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If you are someone like me who have recently upgrade to ASP.NET 4.0, you may have come across Yellow Screen of Death with Http Request Validation Exception, something like:

“A potentially dangerous Request.Form value was detected from the client”

Exception Details : System.Web.HttpRequestValidationException: A potentially dangerous Request.Form value was detected from the client

Surprisingly, you will still see this exception even if you have set ValidateRequest to false in either the Page Tag or Web.Config.

ValidateRequest="false" or  <pages validateRequest="false" />

This may end you being freak out identifying the problem.

The solution is perhaps very simple. I would recommend to go and read ASP.NET 4 Breaking Changes.

“In ASP.NET 4, by default, request validation is enabled for all requests, because it is enabled before the BeginRequest phase of an HTTP request. As a result, request validation applies to requests for all ASP.NET resources, not just .aspx page requests. This includes requests such as Web service calls and custom HTTP handlers. Request validation is also active when custom HTTP modules are reading the contents of an HTTP request.and therefore request validation errors might now occur for requests that previously did not trigger errors.”

In order to revert to the behavior we had previously, you need to add the following setting in Web.config file:

<httpRuntime requestValidationMode="2.0"/>

And this should work!

Hope this helps!

Let's start with the new functionalities introduced in Visual Studio 2012 RC.

Recent Project List

Though this was available in earlier versions of Visual Studio, the option to remove a project from the list is now not available; you can remove unwanted projects from the "Recent" list by selecting the "Remove From List" option. (Right-click on the project you want to remove from the list then select "Remove From List".)

You can even see the latest Visual Studio GUI in the following screen shot:

Visual Studio Dark Theme

I have seen so many developers that don't like the default Visual Studio GUI color and they prefer to code using a dark background. Most of them go to Tools-> Options and change the default color and fonts.

But now you can do this by just changing the Visual Experience. Select Tools -> Options then click on "General" from the "Environment" section. You have the option to select "Dark" or "Light". This is really cool stuff. You can even download themes online.





Visual Studio Installation Engine Improvement

The Visual Studio 2012 installation has become very user-friendly compared to previous versions of Visual Studio. You can save almost 25% of installation time and save about 2.5 GB of space. There is significant improvement in the installation engine.

Other Features

Metro Style Application Development

This is the greatest feature and only available for the Window 8 operating system. To develop a Metro style application, you need to download and install the Windows 8 Release Preview Evaluation copy which is freely available on the Microsoft site. Once you install the Window 8 Release Preview, install Visual Studio 2012 RC.

Select File -> New -> Project which will open the "New Project" window. Select Visual C# or Visual Basic from the Template (my favorite is Visual C#) and go to "Windows Metro style".

Here you have the options to select the kind of Metro style application you want to develop.

(Note: Metro style applications are only available for .Net Framework 4.0 and .Net Framework 4.5.)

Introduction

ASP.NET Web Forms became popular due to the wide range of data bound controls such as GridView, DetailsView and ListView. The earlier versions of ASP.NET, however, were a bit rigid about how data was bound to these controls. Most of the time developers had to use one or the other data source control (SQL Data Source, Object Data Source, Entity Data Source etc.) to bind data from the underlying data store with the data bound controls. ASP.NET 4.5 provides a flexible alternative to data bind these controls - model binding. Using the new model binding features you can use methods instead of data source controls to perform CRUD operations. This article explains how the new model binding features can be used. You will also learn to use strongly typed data controls.

Data Binding in ASP.NET Server Controls

In the earlier versions of ASP.NET you used data bound controls and data source controls hand in hand to display and edit data. First, you needed to configure a data source control, such as Object Data Source or Entity Data Source and then set the DataSourceID property of a data bound control to the respective data source control. The data bound control would have one or more fields of some inbuilt type (BoundField for example) or template fields. If the control was using template fields you used Eval() data binding expression for one way data binding and Bind() data binding expression for two way data binding.

The following sample markup shows a GridView control bound with an Entity Data Source.

<asp:EntityDataSource ID="EntityDataSource1" runat="server"
    ConnectionString="name=NorthwindEntities"
    DefaultContainerName="NorthwindEntities" EnableFlattening="False"
    EntitySetName="Customers"
    Select="it.[CustomerID], it.[CompanyName], it.[ContactName], it.[Country]">
</asp:EntityDataSource>
<asp:GridView ID="GridView2" runat="server" AutoGenerateColumns="False"
    DataKeyNames="CustomerID" DataSourceID="EntityDataSource1">
    <Columns>
        <asp:BoundField DataField="CustomerID" HeaderText="CustomerID" ReadOnly="True"
            SortExpression="CustomerID" />
        <asp:BoundField DataField="CompanyName" HeaderText="CompanyName"
            ReadOnly="True" SortExpression="CompanyName" />
        <asp:BoundField DataField="ContactName" HeaderText="ContactName"
            ReadOnly="True" SortExpression="ContactName" />
        <asp:TemplateField HeaderText="Country" SortExpression="Country">
            <EditItemTemplate>
                <asp:Label ID="Label1" runat="server" Text='<%# Eval("Country") %>'></asp:Label>
            </EditItemTemplate>
            <ItemTemplate>
                <asp:Label ID="Label1" runat="server" Text='<%# Bind("Country") %>'></asp:Label>
            </ItemTemplate>
        </asp:TemplateField>
    </Columns>
</asp:GridView>

Notice how the DataSourceID property of the GridView is set to EntityDataSource1. Also, notice the use of Eval() and Bind() to bind the Country column.

Though data source controls work well in simple situations, developers often need complete control on how the data is fetched and how it is saved back to the database. This calls for a more code centered approach than the control driven approach. That is where the new model binding features come into the picture. Using model binding features you can write methods in your code behind class that perform the CRUD operations on the underlying data store. This way you have total control over the process of fetching and editing the data. Have a look at the following markup that uses the new model binding features:

<asp:GridView ID="GridView1" runat="server"
SelectMethod="GetCustomers"
dateMethod="UpdateCustomer"
DeleteMethod="DeleteCustomer"
... >

This time the GridView control doesn't use a data source control. The SelectMethod, UpdateMethod and DeleteMethod properties are set to method names GetCustomers, UpdateCustomers and DeleteCustomers respectively. These methods reside in the code behind. You will develop a complete version of this example in the following sections.

In addition to the code centered data binding, you can also use data within the controls in strongly typed manner. This is especially handy for template fields. Instead of using Eval() and Bind() data binding expressions, you can now use Item and BindItem properties respectively. These properties work along with the ItemType property. The use of these properties will be clear from the following markup.

<asp:GridView ID="GridView1" runat="server"
SelectMethod="GetCustomers"
UpdateMethod="UpdateCustomer"
DeleteMethod="DeleteCustomer"
ItemType="NorthwindModel.Customer"
... >
<Columns>
...
<asp:TemplateField HeaderText="Country" SortExpression="Country">
  <ItemTemplate>
   <asp:Label ID="Label2" runat="server" Text='<%# Item.Country %>'></asp:Label>
  </ItemTemplate
  <EditItemTemplate>
   <asp:TextBox ID="TextBox2" Text='<%# BindItem.Country %>' runat="server"></asp:TextBox>
  </EditItemTemplate>
</asp:TemplateField>
...

Notice the code marked in bold letters. The ItemType property is set to an Entity Framework Data Model type - Customer. Once you do so, you can access properties of Customer class in a strongly typed fashion. Instead of Eval("Country") you now use Item.Country and instead of Bind("Country") you use BindItem.Country. This way there can't be any errors while specifying column names because they are available to you in the intellisense in strongly typed manner.

Creating a Sample Website

Now that you understand the basics of model binding and strongly typed data binding, let's create a web form that illustrates the complete process in detail. You will be using Customers table from the Northwind database in this example. Begin by creating a new ASP.NET Web Site. Then add an Entity Framework Data Model to its App_Code folder and create model class for the Customers table. The following figure shows the Customers model class in the Visual Studio designer



Open the default web form and place a GridView control on it. Configure the GridView to show CustomerID, CompanyName, ContactName and Country columns. Also add Edit and Delete command buttons. The following markup shows the GridView after adding these columns:

<asp:GridView ID="GridView1" runat="server"
SelectMethod="GetCustomers"
UpdateMethod="UpdateCustomer"
DeleteMethod="DeleteCustomer"
ItemType="NorthwindModel.Customer"
AllowSorting="True"
AllowPaging="True"
DataKeyNames="CustomerID" ...>
    <Columns>
        <asp:BoundField DataField="CustomerID" HeaderText="Customer ID" ReadOnly="True"
            SortExpression="CustomerID"></asp:BoundField>
        <asp:TemplateField HeaderText="Company Name" SortExpression="CompanyName">
            <EditItemTemplate>
                <asp:TextBox ID="TextBox2" Text='<%# BindItem.CompanyName %>' runat="server"></asp:TextBox>
            </EditItemTemplate>
            <ItemTemplate>
                <asp:Label ID="Label2" runat="server" Text='<%# Item.CompanyName %>'></asp:Label>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:BoundField DataField="ContactName" HeaderText="Contact Name"
            SortExpression="ContactName"></asp:BoundField>
        <asp:TemplateField HeaderText="Country" SortExpression="Country">
            <EditItemTemplate>
                <asp:TextBox ID="TextBox3" runat="server" Text='<%# BindItem.Country %>'></asp:TextBox>
            </EditItemTemplate>
            <ItemTemplate>
                <asp:Label ID="Label3" runat="server" Text='<%# Item.Country %>'></asp:Label>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:CommandField ShowEditButton="True" ButtonType="Button">
        <ControlStyle Width="75px" />
        </asp:CommandField>
        <asp:CommandField ShowDeleteButton="True" ButtonType="Button">
        <ControlStyle Width="75px" />
        </asp:CommandField>
    </Columns>
...
</asp:GridView>

The following figure shows the GridView at runtime:



Notice that the ItemType property of the GridView is set to NorthwindModel.Customer and its SelectMethod, UpdateMethod and DeleteMethod properties are set to GetCustomers, UpdateCustomer and DeleteCustomer respectively. You will be creating these methods in the following sections.

Selecting Data

In order to display data in the GridView you need to write a method that fetches data from the data store and then specify it in the SelectMethod property of GridView. So, switch to the code behind and add a method named GetCustomers() as shown below:

public IQueryable<Customer> GetCustomers()
{
    NorthwindEntities db = new NorthwindEntities();
    var data = from item in db.Customers
                orderby item.CustomerID
                select item;
    return data;
}

The GetCustomers() method returns an IQueryable collection of Customer objects. Inside it fetches all of the records from the Customers table and returns them to the caller. Note that we have enabled paging in our GridView. When you enable paging for a GridView, behind the scenes it fetches only the required number of records as specified by the PageSize property.

Updating and Deleting Data

The methods UpdateCustomer() and DeleteCustomer() do the job of updating and deleting a Customer respectively. The UpdateCustomer() method is shown next:

public void UpdateCustomer(Customer c)
{
    NorthwindEntities db = new NorthwindEntities();
    var data = from item in db.Customers
                where item.CustomerID == c.CustomerID
                select item;

    Customer obj = data.SingleOrDefault();
    obj.CompanyName = c.CompanyName;
    obj.ContactName = c.ContactName;
    obj.Country = c.Country;
    db.SaveChanges();
}

The UpdateCustomer() method accepts a parameter of type Customer. At runtime, when you modify a GridView row and click the Update button, UpdateCustomer() method will be called and the corresponding Customer object is passed as its parameter. Inside, you find out a specific Customer based on its CustomerID, assign the modified values and then save the changes to the database by calling the SaveChanges() method.

The DeleteCustomer() method follows a similar method signature but internally deletes a Customer. The following code shows the DeleteCustomer() method:

public void DeleteCustomer(Customer c)
{
    NorthwindEntities db=new NorthwindEntities();
    var data = from item in db.Customers
                where item.CustomerID == c.CustomerID
                select item;
    Customer obj = data.SingleOrDefault();
    db.DeleteObject(obj);
    db.SaveChanges();
}

The DeleteCustomer() method receives the Customer being deleted as a parameter. Inside it fetches a Customer matching the CustomerID and deletes it using the DeleteObject() method.

Now, run the web form and try editing and deleting a few Customer records.

Adding Validation Support

Though the GridView is able to modify Customer data, there are no validations on the data being saved. One way to enforce the validations is to use a combination of template fields and validation controls. However, there is an easy alternative - Data Annotations.

Data Annotations are special attributes that you apply on the data model properties. They specify validation criteria such as maximum length, minimum length and specific data format (Email address, URL etc.).

To use Data Annotations add a new class in the App_Code folder and name it as CustomerValidations. The CustomerValidations class will store only validation information for the Customer class. You could have added the data annotation attributes directly to the Customer data model class but to avoid accidental overwriting during model recreation it is recommended to isolate them in a separate class.

public class CustomerValidations
{
    [StringLength(5,MinimumLength=3 ,ErrorMessage="CustomerID must between 3-5 characters!")]
    public string CustomerID { get; set; }

    [StringLength(20, ErrorMessage = "Company Name must be upto 20 characters!")]
    public string CompanyName { get; set; }

    [Required]
    public string ContactName { get; set; }

    [Required]
    [StringLength(15,ErrorMessage="Invalid country length!")]
    public string Country { get; set; }
}

The CustomerValidations class makes use of data annotation attributes such as [StringLength] and [Required]. The former attribute ensures that the entered data is within a specified maximum length. The later attribute enforces that the property value must be provided. You can also use many other data annotation attributes depending on your requirement.

As of now the CustomerValidations class is a stand alone class. You need to associate it with the Customer data model class using the [MetadataType] attribute. To do so, open the Entity Framework Data Model file (Model.Designer.cs) and add the following piece of code:

[MetadataType(typeof(CustomerValidations))]
public partial class Customer : EntityObject
{
...
}

The [MetadataType] attribute specifies the type of the class that contains validation information (CustomerValidations in this case).

Now, open the web form and place a ValidationSummary control below the GridView. Set its ShowModelStateErrors property to true. The ShowModelStateErrors property controls whether data model validation errors should be displayed in the ValidationSummary or not.

<asp:ValidationSummary ID="ValidationSummary1" runat="server"
ShowModelStateErrors="true" ... />

In addition to displaying validation errors to the end user, you should also ensure that the changed Customer details are saved in the database only if model validations are successful. To do so, modify the UpdateCustomer() method as shown below:

public void UpdateCustomer(Customer c)
{
    NorthwindEntities db = new NorthwindEntities();
    var data = from item in db.Customers
                where item.CustomerID == c.CustomerID
                select item;
    Customer obj = data.SingleOrDefault();
    obj.CompanyName = c.CompanyName;
    ...
    if (ModelState.IsValid)
    {
        db.SaveChanges();
    }
}

Notice the code marked in bold letters. The UpdateCustomer() method now checks the state of the model using the ModelState.IsValid property. If all the model validations are successful, the IsValid property will return true and only then will changes be saved to the database.

Now, run the web form again and try to enter some invalid data. You should see validation errors similar to the following figure:



Summary

ASP.NET 4.5 supports model binding that allows a more code centric approach for performing CRUD operations on the data. Instead of using Data Source Controls, you can now write methods in the code behind file that select, insert, update and delete data from the underlying data store. The SelectMethod, InsertMethod, UpdateMethod and DeleteMethod properties of data bound controls are used to specify the respective method. You can also make use of Data Annotations for performing validations on the data being entered. Thus the new model binding features provide a more flexible and powerful approach to data binding.

Introduction

Asynchronously running code can improve the overall performance and responsiveness of your web application. In ASP.NET 4.5 web forms applications you can register asynchronous methods with the page framework. The ASP.NET page framework and .NET 4.5 asynchronous programming support then executes the operations in asynchronous fashion. This article shows how this can be done.

Example Scenario

Consider that you have a web application that needs to call two ASP.NET Web API services namely Customer and Product. These services return Customer and Product data from the Northwind database respectively. Now, assume that each of these services take 5 seconds to complete the data retrieval operation. If you use synchronous mode for calling these services then the total time taken will be 10 seconds. Because the execution will happen sequentially - first Customer service will complete and then Product service will complete.

On the other hand if you invoke these services in asynchronous fashion, the service operations won't block the caller thread. The Customer service will be invoked and control will be immediately returned to the caller. The caller thread will then proceed to invoke the Product service. So, two operations will be invoked in parallel. In this case the total time taken for completing both of the operations will be the time taken by the longest of the operations (5 seconds in this case).

Async, Await, Task and RegisterAsyncTask

Before developing web forms applications that execute asynchronous operations you need to understand a few basic terms involved in the process.

A task is an operation that is to be executed in asynchronous fashion. Such an operation is programmatically represented by the Task class from System.Threading.Tasks namespace.

When an asynchronous operation begins, the caller thread can continue its work further. However, the caller thread must wait at some point of time for the asynchronous operation to complete. The await keyword invokes an asynchronous operation and waits for it to complete.

The async modifier is applied to a method that is to be invoked asynchronously. Such an asynchronous method typically returns a Task object and has at least one await call inside it.

Just to understand how async, await and task are used at code level, consider the following piece of code:

public async Task<MyObject> MyMethodAsync()
{
  MyObject data = await service.GetDataAsync();
  //other operations on data go here
  return data;
}

Here, method MyMethodAsync() is marked with async modifier. By convention, asynchronous method names end with "Async". The MyMethodAsync() returns MyObject wrapped inside a Task instance. Inside the method a remote service is invoked using GetDataAsync(). Since MyMethodAsync() needs to return data retrieved from the service, the await keyword is used to wait till the GetDataAsync() method returns. Once GetDataAsync() returns the execution is resumed and further code is executed. The data is finally returned to the caller.

NOTE:
For a detailed understanding of async, await and Task refer to MSDN dicumentation. Here, these terms are discussed only for giving a basic understanding of the respective keywords.

ASP.NET page framework provides a method - RegisterAsyncTask() - that registers an asynchronous task with the page framework. Tasks registered using the RegisterAsyncTask() method are invoked immediately after the PreRender event. The RegisterAsyncTask() method takes a parameter of type PageAsyncTask. The PageAsyncTask object wraps the information about an asynchronous task registered with a page. The following piece of code shows how they are used:

protected void Page_Load(object sender, EventArgs e)
{
   PageAsyncTask task = new PageAsyncTask(MyMethod);
   RegisterAsyncTask(task);
}

Asynchronous Solution

Now that you are familiar with the basic concepts involved in utilizing asynchronous operations in a web forms application, let's create a sample application that puts this knowledge to use.

Begin by creating two projects - an empty web forms application and an ASP.NET MVC4 Web API application.

Add an Entity Framework Data Model for the Customers and Products tables of the Northwind database. Place the EF data model inside the Models folder.



Add an Entity Framework Data Model for the Customers and Products tables

Add two ApiController classes to the Web API project and name them as CustomerController and ProductController.



Add two ApiController classes

Then add Get() methods to both the ApiController classes as shown below:

public class CustomerController : ApiController
{
    public IEnumerable<Customer> Get()
    {
        Northwind db = new Northwind();
        var data = from item in db.Customers
                    select item;
        System.Threading.Thread.Sleep(5000);
        return data;
    }

}
public class ProductController : ApiController
{
    public IEnumerable<Product> Get()
    {
        Northwind db = new Northwind();
        var data = from item in db.Products
                    select item;
        System.Threading.Thread.Sleep(5000);
        return data;
    }

}

The Get() method of the CustomerController class selects all the Customer records from the Customers table whereas the Get() method of the ProductController class selects all the Product records. For the sake of testing, a delay of 5 seconds is introduced in each Get() method. The Get() methods return an IEnumerable collection of Customer and Product objects respectively.

Now, go to the web forms project and open the code behind file of the default web form. Here, you will write a couple of private methods that invoke the Web API developed previously. These methods are shown below:

public async Task<List<Customer>> InvokeCustomerService()
{
    using (HttpClient client = new HttpClient())
    {
        HttpResponseMessage response = await client.GetAsync("http://localhost
        string json= (await response.Content.ReadAsStringAsync());
        List<Customer> data = JsonConvert.DeserializeObject<List<Customer>>(json
        return data;
    }
}

public async Task<List<Product>> InvokeProductService()
{
    using (HttpClient client = new HttpClient())
    {
        HttpResponseMessage response = await client.GetAsync("http://localhost
        string json = (await response.Content.ReadAsStringAsync());
        List<Product> data = JsonConvert.DeserializeObject<List<Product>>(json
        return data;
    }
}

The InvokeCustomerService() method invokes the Customer Web API whereas InvokeProductService() method invokes Product Web API. Both the methods essentially use an HttpClient to get data from the respective Web API. Notice that both the methods have async modifier and return a Task instance that wraps the actual return type (List<Customer> and List<Product> respectively). The GetAsync() method of the HttpClient object is an asynchronous method. Call to the GetAsync() is marked using the await keyword so that further statements are executed only when GetAsync() returns. The GetAsync() method accepts a URL of the respective Web API. Make sure to change the port number as per your development setup. The GetAsync() method returns an HttpResponseMessage object. The actual data is then retrieved using ReadAsStringAsync() method of the Content property. The ReadAsStringAsync() will return data as a JSON string. This JSON data is converted into a .NET generic List using DeserializeObject() method of the JsonConvert class. The JsonConvert class comes from the Json.NET open source componenet. You can download Json.NET here.

The InvokeCustomerService() and InvokeProductService() methods are called inside another private method GetDataFromServicesAsync() as shown below:

private async Task GetDataFromServicesAsync()
{
    Stopwatch stopWatch = new Stopwatch();
    stopWatch.Start();

    var task1 = InvokeCustomerService();
    var task2 = InvokeProductService();

    await Task.WhenAll(task1, task2);

    List<Customer> data1 = task1.Result;
    List<Product> data2 = task2.Result;

    stopWatch.Stop();
    Label2.Text = string.Format("<h2>Retrieved {0} customers and {1} products
                                 data1.Count, data2.Count, stopWatch.Elapsed.TotalSeconds
}

As shown above, GetDataFromServicesAsync() is also marked as async and returns a Task instance. Inside, a StopWatch class from System.Diagnostics namespace is used to find the time taken by both of the operations to complete. InvokeCustomerService() and InvokeProductService() methods are then called. The returned Task instance is stored in task1 and task2 variables respectively. The WhenAll() method of Task class creates another Task that completes when all the specified tasks are complete. In this case it creates a Task that completes after complition of task1 and task2. Actual data returned by the respective Web API is retrieved using the Result property of the respective Task objects. The time taken to complete the operation is measured by the StopWatch and is displayed in a Label.

The next step is to register GetDataFromServicesAsync() with the page framework. This is done using the RegisterAsyncTask() method as shown below:

protected void Page_Load(object sender, EventArgs e)
{
    RegisterAsyncTask(new PageAsyncTask(GetDataFromServicesAsync));
}

As you can see, Page_Load event handler registers an asynchronous task using RegisterAsyncTask() method. The RegisterAsyncTask() method accepts an instance of PageAsyncTask. The PageAsyncTask instance in turn wraps the GetDataFromServicesAsync() method created earlier.

The final step is to set Async attribute of the @Page directive to true:

<%@ Page Async="true" Language="C#" CodeBehind="WebForm1.aspx.cs" ... %>

The Aync attribute of the @Page directive indicates that this web form will be executed in asynchronous fashion. Web forms that use RegisterAsyncTask() method must set the Async attribute to true, otherwise an exception is raised at runtime.

This completes the application and you can test it by running the web forms application. The following figure shows a sample run of the web form:



A sample run of the web form

Though the code doesn't show the synchronous execution of the Web API operations, for the sake of better understanding the above figure shows time taken for synchronous as well as asynchronous execution. Recollect that both the Get() methods sleep for 5 seconds and hence the synchronous execution takes approximately 10 seconds. However, the asynchronous execution takes approximately 5 seconds. As you can see the asynchronous operation improves the overall performance of the application.

Summary

Using async and await keywords you can create operations that run asynchronously. Such asynchronous tasks can be registered with the page framework using RegisterAsyncTask() method. Registered tasks run immediately after the PreRender event of the web form. Asynchronous operations can improve the overall performance and user responsiveness of a web application.

New Features in HTML5

HTML5 is an umbrella term for the new HTML, JavaScript, and Cascading Style Sheets (CSS) features that are being standardized. New HTML tags include the <nav> tag, which is used for general website navigation; the <video> tag, which is used for displaying video content; and the <audio> tag, which is used for playing audio content. In general, these tags replace the <object> tag that websites used previously. HTML5 also includes new input controls that are designed to handle some of the more common input scenarios, such as issues with dates and times. Finally, numerous attributes have been added to existing controls. Many of the existing input controls have new and enhanced attributes that allow browsers to expose users to new functionality.

Along with the new markup specifications, new JavaScript classes let programmers capitalize on the latest features that developers have been asking for. The following paragraphs discuss some of these features.

JavaScript selectors. There are new JavaScript selectors for getElementById and getElementByTagName. There are also selectors, such as getElementByClassName and querySelector.

LocalStorage. Developers have long been using cookies for local storage. However, cookies are sent across the wire and back to the server, a transfer that increases sent data volumes. HTML5 introduces support for a storage feature named LocalStorage. With this feature, data is no longer sent across the wire with each server request. Also, more data can be stored with LocalStorage than with cookies.

WebSQL. Although WebSQL is no longer a part of the HTML5 standard, this feature has been implemented in several browsers, such as iPhone's Safari and the Android browser. This feature can be tested for and used.

Threads. On a desktop application, a long-running operation can be spun off into another thread, allowing the user to continue working without blocking the application's UI. HTML5 introduces this concept of threads in the browser environment, a feature known as Web Workers.

Application caching. What happens when an application cannot connect to its web server? There may be a variety of reasons, but the user only knows that the application is offline. HTML5 provides an offline application-caching API that allows an application to degrade more gracefully when it cannot connect to its web server.

Web sockets. When there is a long-running event on the server, the browser can be set to poll for a completion. What happens when 100,000 users continually nag the server with the online equivalent of "Are we there yet?" To address this issue, the HTML5 standard has web sockets. However, there are some security issues in the underlying communications protocol that must be addressed.

Drawing. It's possible to draw in the browser by using the Canvas tag and its associated JavaScript commands.

Geolocation . Geolocation is not a part of, but is associated with, the HTML5 specifications. Because it is often discussed as a part of HTML5, we'll consider it that way for this article. Geolocation allows a browser to determine its current location so that the user can be presented with local information. Geolocation allows for more accurate location information than is typically possible through IP address lookup services.

Other features allow for drag-and-drop support, audio and video tag manipulation, server-sent events, and other features. Some of these features will also require server support for optimal performance.

A Peek at HTML5

Let's take a peek at a simple HTML5 web page and make some key observations about the code. Figure 1 shows some sample source code.

Figure 1: Sample HTML5 source code

<!DOCTYPE html>
 <html lang="en">
     <head>
         <meta charset="utf-8" />
         <meta http-equiv="X-UA-compatible" content="IE=edge,chrome=1" />
         <title>About My HTML5 Site</title>

    </head>
     <body>
     <div id="container">
             <header  >               

                <h1>About My HTML5 Site</h1>
             </header>
                 <p>
     This web page was built using ASP.NET. For more information, visit the
     <a href="http://www.asp.net">ASP.NET homepage</a>.
 </p>
             <footer>               

                <span style="margin-left:auto;margin-right:auto;"><a href="http://www.scalabledevelopment.com">SDI</a></span>
             </footer>
         </div>
     </body>
 </html>

Notice that the doctype tag, which tells a browser which version of HTML to use, is now much simpler. In HTML5, there is only one doctype tag. The X-UA-Compatible meta tag tells the browser to use the most recent engine available. My system has the Google Chrome frame plug-in installed, so this information is included, as well as the instruction to use the most recent version of the Internet Explorer (IE) engine. Finally, the page is logically divided by header, content, and footer tags. These tags instruct a browser to separate the content visually. This instruction is particularly important for a mobile web browser.

Browsers Galore

Currently, there is no single dominant browser. We've got IE, Firefox, Chrome, Safari, and Opera for the desktop. Add to those the many mobile device browsers such as Safari, the Android browser, and the mobile IE for Windows Phone 7, along with the various versions of each browser. Developers are presented with a vast and complex array of scenarios to code for. In this vein, you may be familiar with the following JavaScript code:

If ( navigator.useragent.indexOf(…….) > -1)
{
// do something...

This code determines whether the browser is of a specific type. It then responds accordingly—for example, by redirecting the browser to a page optimized for that browser.

Similar functionality exists on the server. The ASP.NET developer can use the Request.Browser server-side object. Some of the properties of this object that you may find useful include the following:

• Request.Browser.IsMobileDevice
• Request.Browser.MobileDeviceManufacturer
• Request.Browser.MobileDeviceModel
• Request.Browser.ScreenPixels

Along with the Request.Browser server-side object, ASP.NET controls contain support for various browsers, based on the user-agent header value. You can also use the Wireless Universal Resource File (WURFL) project. The WURFL project contains a more current set of browser definitions that allow a user to determine device features on the server, such as device input method, audio format support, and other features that are not part of the built-in ASP.NET capabilities. This general technique is referred to as browser detection. While conceptually simple, browser detection tends to be problematic. Browser detection typically results in a large number of if/else statements. This can be confusing and difficult to change.

Feature detection is another useful HTML5 option. A browser is tested for its support of various features. If it supports a particular feature, the browser uses it; if support for the feature is not available in the browser, the feature is not used. Although slightly different from browser detection, feature detection results in simpler code that is ultimately easier to maintain. Although browser detection was fairly common for years, feature detection is better for creating maintainable code.

Along with feature detection, a JavaScript library named Modernizr helps developers implement reliable feature detection. The following code sample uses the Modernizr library to test for geolocation support and then apply geolocation.

       if (Modernizr.geolocation) {
             var navgeo = navigator.geolocation;
             navgeo.getCurrentPosition(WhereIsUser, WhereIsUserError, PosOptions);
         }

Native IE9

At the MIX11 conference, Microsoft made a lot of predictable noise in support of IE because of its "native" status. Terms like native HTML were bandied about. Add to that an early June 2011 demo of Windows 8 with HTML and JavaScript, and there has been some understandable confusion in the marketplace. With all these terms and ideas being tossed around, what's a developer to do? Microsoft will have its BUILD conference in September, so hopefully we'll know more then. In the mean time, there are a few things that we do know about IE9 regarding its optimizations and hardware acceleration.

First, we know that the JavaScript engine has been rewritten to support multiple processor cores. Specifically, a background compilation takes JavaScript and converts it into machine code that runs faster on a given system. Secondly, the machine code that the JavaScript engine produces takes advantage of the most recent and optimized machine commands. Finally, we know that the HTML, Scalable Vector Graphics (SVG), CSS, audio, and video support have been reconfigured for hardware acceleration. Microsoft may have added these features to support modern hardware capabilities such as graphics processing units (GPUs), multiple cores, and other new developments. For example, the <canvas> tag will attain a big boost in performance when it is used in IE9. Overall, it appears that the folks at Microsoft are promoting their browser as the best platform because there are fewer operating system layers to go through when you use IE in a Windows environment.

How ASP.NET Developers Can Be Involved

If you're an ASP.NET developer, you're faced with a couple of questions when designing an ASP.NET application to support HTML5. The first question concerns how to present an application to the user. Currently, HTML5 browsers are more frequently found in mobile devices than in desktop browsers. Since there is a profound difference between a four-inch mobile device and a 25-inch desktop browser, you must understand the differences between the two. A web application designed for a desktop browser (as shown in Figure 2) will most likely present a horrible experience to a user who connects to the application over a mobile device (as shown in Figure 3).





Given the significant differences in device dimensions, successful sites, such as ESPN and Ruby Tuesday design their applications for a general display size. If a user comes to a site through a desktop browser, the user goes right on into the site. If a user comes to a site through a mobile browser, the user is redirected to a mobile version of the application. The code to detect the type of browser and perform the redirection can be placed within the session's Start event.

The second question concerns which ASP.NET display technology to use. Thankfully, it doesn't matter if an application uses ASP.NET Web Forms, ASP.NET MVC, or ASP.NET Web Pages (aka Razor). All these technologies can be used to build an HTML5 ASP.NET application. ASP.NET, MVC, and Web Pages let you directly interact with the HTML output, so you don't need to do anything special when using these types of projects. You only need to write valid HTML5 code for the devices you're planning to support. With a few changes of the standard features in ASP.NET Web Forms, you can use HTML5 features quickly and easily.

Web Forms

ASP.NET Web Forms is a very popular development framework. The problem with Web Forms is that some of its standard features create confusion. The most problematic features in HTML5 and mobile spaces are ViewState, ClientIDs, and MasterPages. We'll walk through ways to provide users with a more optimal solution to the problems encountered when using these features.

ViewState. ASP.NET developers are used to working with ViewState, the feature that makes Web Forms work. However, ViewState increases the size of the web page. For example, if you bind a set of objects to a grid, the size of the page increases dramatically. While the size of the page is not necessarily a big deal for applications that are running over a fairly reliable network, increased page size greatly increases the risk of an error when the page is transmitted over wireless 3G and 4G networks. To work around this issue, you have two options.

First, you can turn off ViewState unless it's needed by a specific control on a page. When you turn off ViewState, it is minimized unless it's absolutely needed, as determined by a developer. However, a page may still be too large because ViewState is stored on the client web page. In this scenario, ViewState can be turned off at the container, page, application, or server level. Turning it off at these levels eliminates the ViewState payload unless it's absolutely necessary for a control.

ASP.NET 4 introduces a feature that lets you turn off ViewState at a higher level in the hierarchy, then turn it on as necessary. Specifically, ViewState can be modified by the ViewStateMode attribute in an ASP.NET control. In the examples in Figure 4 and Figure 5, a grid of data is displayed to the user. The GridView doesn't require many of the more complicated features typically associated with HTML5, so turning off ViewState has no effect on the application or the user. Note that the ViewState mode is turned off within the Content2 container. Figure 4 shows the code for the content view. Figure 5 shows the output of the code in Figure 4.

Figure 4: Code for the content view

<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server" ViewStateMode="Disabled">
 <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.6.1/jquery.min.js"></script>
 View State Size: <span id="ViewStateSize"></span>
 <script language="javascript" type="text/javascript">
     $(document).ready(function () {
         // put all your jQuery goodness in here.
         var vs = document.getElementById("__VIEWSTATE");
         var outPut = document.getElementById("ViewStateSize");
         outPut.innerHTML = vs.value.length;
     });
 </script>
 <asp:GridView ID="gvCustomer" runat="server">
 <Columns>
 <asp:TemplateField AccessibleHeaderText="Get Info" HeaderText="Get Info">
 <ItemTemplate>
     <asp:HyperLink ID="hl" runat="server" Text="Get Info"
         NavigateUrl='<%# String.Format("CustomerInformation.aspx?CustomerID={0}", Container.DataItem) %>' />
 </ItemTemplate>
 </asp:TemplateField>
 </Columns>
 </asp:GridView>
 </asp:Content>



The second option is to store ViewState on the server. When you use this option, the data is never transferred across the wireless connection. This requires some setup on the pages, but once configured, this option is relatively painless. There are a number of articles about this topic on the web, so there's not much reason to go over the details here.

ClientIDs . Automatically generated ClientIDs represent the next issue that ASP.NET developers must negotiate. By default, the client IDs that are generated comprise a munged version of the server-side parent containers and control IDs. For example, the grid shown in the ViewState example has the ID MainContent_gvCustomer. You can use the following JavaScript command to get a client-side reference to a server-side object:

var serverObject = document.getElementById('<%: gvCustomer.ClientID%>');

Unfortunately, developers are not the only folks who work on a project. Designers are also involved, and they may not be familiar with the functionality behind control IDs. Therefore, a new feature was introduced in ASP.NET 4 to grant programmers complete control over the client IDs that are generated. This feature is controlled by the ClientIDMode attribute. The values of particular interest for this attribute are Static and Predictable. The Static attribute makes sure that the client ID that is generated remains the same as the server ID. The Predictable attribute is used in conjunction with the data-bound controls and the Static value to generate repeatable client IDs in a grid.

MasterPages. Although not necessarily a requirement for Web Forms developers, MasterPages is a great tool for sharing display layout among pages. I don't recommend that you try to use the same general layout for both a desktop web application and a mobile web application. Instead, it makes sense to create a master page optimized for mobile devices and to continue using this design and layout technique, although MasterPages will certainly be different because of the difference in the layout capabilities of a mobile device and a desktop web browser.

HTML5 Validation

In the Visual Studio 2010 SP1 release, the April 2011 ASP.NET MVC 3 Tools update, and the June 2011 release of the Visual Studio Web Standards update, Microsoft not only updated its MVC tools, but it also added support for HTML5, as illustrated in Figures 6A and 6B. Developers now get support for HTML5, CSS3, and the JavaScript objects that support the new features. With CSS3 support, even the IE, Mozilla, and Safari extensions are supported.





Saving Bandwidth with CDNs

Most developers are accustomed to copying files locally to a solution, then running the application as a self-contained unit. There are a number of files that applications share, not only across a single company but also across many applications. These are libraries such as jQuery and many of the JavaScript libraries that are a part of the ASP.NET 4 framework. Many companies and organizations share these libraries. Instead of using this bandwidth on your servers and routinely downloading these files, based on caching settings, it makes sense to use the same copies that others may have already downloaded to their systems. This means that instead of loading JavaScript files, CSS files, and others from your web server, the user's browser downloads the files from various content delivery networks (CDNs). Although this approach may not sound like a significant improvement, your users will typically obtain a better response time for various libraries from these CDNs. Along with shipment of ASP.NET 4, Microsoft has provided support for its CDN within the ASP.NET ScriptManager by setting the EnableCdn attribute to true.

To illustrate the difference between using a CDN and using content from your own local web server, let's look at the results from a simple ASP.NET Web Form by using the Firebug and YSlow tools. Let's look at a simple page with only the master page and the script manager installed, as shown in Figure 7.



Once the four standard ASP.NET JavaScript files are cached locally, 56.6KB of data is being pulled from the local cache. This may not sound like a lot of data, but in an HTML5 mobile world, this amount can be significant.

Now, what would have happened if we had not used the CDN? As you can see from Figure 8, YSlow reports that the files are cached coming from our own web server.



However, it is highly unlikely that other applications are pulling this content from our servers; at least we hope that they aren't. By using the files from our local server, users are paying the "bandwidth tax" instead of using the files that may already be cached locally from another application. Every little bit of bandwidth savings helps, especially in the mobile space. A second advantage is that on public-facing websites where bandwidth may cost money, the bandwidth cost for your website will most likely go down by using a CDN. For more information about why to cache files through CDNs, check out Dave Ward's excellent set of articles in the Links of Interest sidebar at the end of this article

ASP.NET MVC

In pages and applications based on the MVC design pattern, the presentation logic is decoupled from the underlying application logic. If an application needs to present different views of the same data to a desktop and a mobile client web client, it is possible to reuse the underlying models and controllers and merely swap the views as necessary. I think this is a huge win for web developers who are using the ASP.NET MVC framework.

With the recent MVC3 Tools update, the ASP.NET team has added the ability to use HTML5 by default. You can do so by selecting the Use HTML5 semantic markup check box, as shown in Figure 9.

In early .NET versions if someone asked, can we implement caching in a Console Application, Windows Presentation Foundation Application and other .NET Applications other than ASP.NET application then people would laugh at this question but now with .NET 4.0 and above framework we can cache data in all types of .NET applications such as Console Applications, Windows Forms and Windows Presentation Application etc.

Let's see what is a new thing in the .NET 4.0 framework. They introduce a new library System.Runtime.Caching that implements caching for all types of .NET Applications.

Reference: http://msdn.microsoft.com/en-us/library/dd985642

Let's try to implement caching in a Console Application.

Step 1: First of all we will create a new Console Application. I have given it the name SystemRuntimeCachingSample40.

Step 2: Now we will try to add a System.Runtime.Caching assembly to our project but unfortunately you will not find that assembly because by default your target framework is .NET Framework 4 Client Profile.





You must change it from client profile to .NET famework 4.



Now you can find the assembly; see the following image:



Step 3: Now everything is set up.

This is the code for caching

static void Main(string[] args)
{  

    for (int i = 0; i < 2; i++)
    {
        ObjectCache cache = MemoryCache.Default;
        CacheItem fileContents = cache.GetCacheItem("filecontents");
        if (fileContents == null)
        {
            CacheItemPolicy policy = new CacheItemPolicy();
            List<string> filePaths = new List<string>();
            string cachedFilePath =
@"C:\Users\amitpat\Documents\cacheText.txt";
            filePaths.Add(cachedFilePath);
            policy.ChangeMonitors.Add(new HostFileChangeMonitor(filePaths));
            string fileData = File.ReadAllText(cachedFilePath);
            fileContents = new CacheItem("filecontents", fileData);
            cache.Set(fileContents, policy);
       }
         Console.WriteLine(fileContents.Value as string);
     }
    Console.Read();
}

When you run your application you will see that for the second time it will not go into the IF block.

Happy Coding.

Main Advantage of Session StateServer (Best to choose while hosting on third party server)

1. Session is persistent and reliable.
2. Avoid Session Timeout due to Memory shortage on server (IIS Setting).

Main Disadvantage

1. Poor Performance compare to Session="InProc"
2. Session_End Event would not fire.

Steps for changing Session InProc Mode to Session StateServer Mode.

Step 1: Start Asp.net State Servcie

1. Go to Control Panel > Administrative Tools > Services

2. Select Asp.Net State Service.

3. Right Click on Asp.net State Service and choose start from popup menu.





If you forget to Start Service you will receive following error.

Server Error in '/' Application.

Unable to make the session state request to the session state server. Please ensure that the ASP.NET State service is started and that the client and server ports are the same. If the server is on a remote machine, please ensure that it accepts remote requests by checking the value of HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\aspnet_state\Parameters\AllowRemoteConnection. If the server is on the local machine, and if the before mentioned registry value does not exist or is set to 0, then the state server connection string must use either 'localhost' or '127.0.0.1' as the server name.

Step 2: Change Session Mode in Web.Config File

<sessionState mode="StateServer"
                stateConnectionString="tcpip=127.0.0.1:42424"
                cookieless="false"
                timeout="120"/>

Note: You can adjust timeout minutes based on your requirement. Let the tcpip server to be localhost i.e. 127.0.0.1. Most webhosting company uses these settings unless you have different IP for StateServer and You are not required to change Port Number.

Step 3: Make All Object Serializable

You should make all object in your website to serializable.

Note: To take advantage of Session StateServer or SQLServer or Custom Mode, object needs to be serialized.

Example: If your project contains class files for creating DAL (Data Access Layer), you should append Serializable to every class definition in order to make class Serializable.

[Serializable]

Class Department
{
          long _deptId;
          string _deptName;

          public long DeptId
          {
                    get { return _deptId; }
                    set { _deptId = value; }
          }

          public string DeptName
          {
                   get { return _deptName; }
                   set { _deptName = value; }
          }
}

IMPORTANT While doing Serialization

Remember SQLConnection cannot be serialized.

You might receive following error if you don't handle this situation.

Unable to serialize the session state. In 'StateServer' and 'SQLServer' mode, ASP.NET will serialize the session state objects, and as a result non-serializable objects or MarshalByRef objects are not permitted. The same restriction applies if similar serialization is done by the custom session state store in 'Custom' mode.

So to handle this situation you need to do following thing.

1. Mark SQLConnection Object as NonSerialized [NonSerialized] protected SqlConnection _mainConnection;

2. Mark your Class as Serializable and derive from IDeserializationCallback
Example:

[Serializable]

Class Department: IDeserializationCallback
{
    long _deptId;
    string _deptName;

    public long DeptId
    {
        get { return _deptId; }
        set { _deptId = value; }
    }

    public string DeptName
    {
        get { return _deptName; }
        set { _deptName = value; }
    }

    //Create this Method Inside your Class
    void IDeserializationCallback.OnDeserialization(object sender)
    {
       //Recreate your connection here
       _mainConnection = new SqlConnection();
       _mainConnection.ConnectionString =
            ConfigurationSettings.AppSettings["connStr"].ToString();
    }
}

In this article, I will show you new features in ASP.NET 4.5, Asynchronous HTTP Module.

First Just to give a brief Idea, why Asynchronous HTTPModules are important ?

As we all know, web is stateless. A Web page is created from scratch every time whenever it is posted back to the server. In traditional web programming, all the information within the page and control gets wiped off on every postback. Every request in ASP.NET goes through a series of events.

Every request is served by am HTTP handler and it goes a series of HTTPModules (HTTPPipeline) which can be read, update the request. A lot of features of ASP.NET like Authentication, Authorization, Session etc are implemented as HTTP Module in ASP.NET. Let’s have a view on the Request Processing



Now as you can see the request is assigned to a thread T1 from the available threads is thread pool. And the request is passed through several HTTPModules and finally served my HTTPHandler and response is send back with the same thread (T1).

During the entire processing, same thread is engaged in serving the same request and cannot be used by any another request till request processing completes. During the request processing if any HTTPModules depends on some entities like I/O based operations, web services, Databases queries etc then it takes long to complete which makes the thread busy for long which makes asp.net thread will not do anything during that duration and will be useless. In this kind of scenarios the throughput goes down rapidly.

In the above scenario, synchronous HTTPModule can degrade the site performance a lot. So if we can make HTTPModules as asynchronous that can increase the through put a lot. In asynchronous mode, ASP.NET thread get released as soon as the control get passed to another component/module, it does not wait. And the thread becomes available in thread pool and can be used to serve another request. When the component completes its assigned task then it got assigned to new ASP.NET thread which completes the request. The flow can be graphically presented as



In the above picture, An asp.net thread T1 is assigned from threadpool to server the request. When the control got passed to File System to log message, asp.net thread got released and when essage logging got completed, control passed to asp.net and it is assigned to another thread say T2 from thread pool.
In .NET Framework 4.o, there was some major enhancement made for asynchronous programming model. Any asynchronous operation is represents a Task and it comes under the namespace System.Threading.Tasks.Task.

In .NET 4.5, there are some new operator and keyword introduced that makes the life easy for implement Asynchronous feature. One is async keyword and await operator.

These two enables us to write the asynchronous code is similar fashion as we write for synchronous mode.

And these features can be easily used while writing HTTPModules and HTTPHandlers. We’ll be using these enhancements in writing our custom asynchronous HTTPModule.

In my sample as depicted in image, I am creating a module that writes some log messages in a text file for every request made.

So to create a Custom HTTPModule, Create a class library project. And create a class say named LogModule which implements IHttpModule. For this you need to add a reference of Assembly System.Web.

LogModule would contains the methods discussed below.

We need to implement two methods Init and Dispose that are part of IHTTPModule interface.

Here first , I have written an asynchronous method that actually reads the information from the request and writes in the log file asynchronously . For this I have used WriteAsync of FileStream

private async Task WriteLogmessages(object sender, EventArgs e)
{
    HttpApplication app = (HttpApplication)sender;
        DateTime time = DateTime.Now;

        string line = String.Format(
        "{0,10:d}    {1,11:T}    {2, 32}   {3}\r\n",
        time, time,
        app.Request.UserHostAddress,
        app.Request.Url);
        using (_file = new FileStream(
            HttpContext.Current.Server.MapPath(
              "~/App_Data/RequestLog.txt"),
            FileMode.OpenOrCreate, FileAccess.Write,
            FileShare.Write, 1024, true))
        {
            line = line + "  ," + threaddetails;
            byte[] output = Encoding.ASCII.GetBytes(line);

            _file.Seek(_position, SeekOrigin.Begin);
            _position += output.Length;
            await _file.WriteAsync(output, 0, output.Length);
        }

}

Here you can see the await key word, what it means..

As per msdn “An await expression does not block the thread on which it is executing. Instead, it causes the compiler to sign up the rest of the async method as a continuation on the awaited task. Control then returns to the caller of the async method. When the task completes, it invokes its continuation, and execution of the async method resumes where it left off.“

await is used with some asynchronous method that returns task and is used suspend the execution of the method until the task completes and control is returned back to the caller to execute further. await should be used with the last expression of any code block.

And Init method would be like

public void Init(HttpApplication context)
{
        // It wraps the Task-based method
        EventHandlerTaskAsyncHelper asyncHelper =
           new EventHandlerTaskAsyncHelper(WriteLogmessages);

        //asyncHelper's BeginEventHandler and EndEventHandler eventhandler that is used
        //as Begin and End methods for Asynchronous HTTP modules
        context.AddOnPostAuthorizeRequestAsync(
        asyncHelper.BeginEventHandler, asyncHelper.EndEventHandler);

}

So apart from above these methods, we need to implement the dispose method.

Now compile your class library and use the reference in your ASP.NET website . Now as you must be knowing that we need to need to add the entry in the config file. So it’ll be as

<system.webServer>
<modules>
<add name="MyCustomHTTPModule" type="MyCustomHTTPModule.LogModule, MyCustomHTTPModule"/>
</modules>
</system.webServer>

Now when you run your application, you will see the logs are created in a text file in App_Data folder as mentioned path in the code.

Hope you all have liked this new feature.

In this article I am trying to explain Custom Caching Provider in ASP.NET 4.0 or 4.5. I have created a sample in Visual Studio 2011.

Purpose

Caching enables you to store data in memory for rapid access. When the data is accessed again, applications can get the data from the cache instead of retrieving it from the original source. This can improve performance and scalability. In addition, caching makes data available when the data source is temporarily unavailable.

Code:

Step 1 : Create two new projects; one is Web Application and the other is Class Library.

Step 2: Now open the Class Library project and add a reference for System.Web assembly.

Step 3: Now inherit your class from OutputCacheProvider Class.

Step 4: Now override all Add, Get, Set and Remove Methods.

Here is sample Code.

public class FileCacheProvider : OutputCacheProvider
    {
        private string _filecachePath;

        public string FilecachePath
        {
            get
            {
                if (!string.IsNullOrEmpty(_filecachePath))
                    return _filecachePath;
                _filecachePath = System.Configuration.ConfigurationManager.AppSettings["OutputCachePath"];

                var context = HttpContext.Current;

                if (context != null)
                {
                    _filecachePath = context.Server.MapPath(_filecachePath);
                    if (!_filecachePath.EndsWith("\\"))
                        _filecachePath += "\\";
                }

                return _filecachePath;
            }
        }
        public override object Add(string key, object entry, DateTime utcExpiry)
        {
            Debug.WriteLine("Cache.Add(" + key + ", " + entry + ", " + utcExpiry + ")");

            var path = GetPathFromKey(key);

            if (File.Exists(path))
                return entry;

            using (var file = File.OpenWrite(path))
            {
                var item = new CacheItem { Expires = utcExpiry, Item = entry };
                var formatter = new BinaryFormatter();
                formatter.Serialize(file, item);
            }

            return entry;
        }
        public override object Get(string key)
        {
            Debug.WriteLine("Cache.Get(" + key + ")");
 
            var path = GetPathFromKey(key);

            if (!File.Exists(path))
                return null;

            CacheItem item = null;

            using (var file = File.OpenRead(path))
            {
                var formatter = new BinaryFormatter();
                item = (CacheItem)formatter.Deserialize(file);
            }

            if (item == null || item.Expires <= DateTime.Now.ToUniversalTime())
            {
                Remove(key);
                return null;
            }

             return item.Item;
        }
        public override void Remove(string key)
        {
            Debug.WriteLine("Cache.Remove(" + key + ")");

            var path = GetPathFromKey(key);

            if (File.Exists(path))
                File.Delete(path);
        }

        public override void Set(string key, object entry, DateTime utcExpiry)
        {
            Debug.WriteLine("Cache.Set(" + key + ", " + entry + ", " + utcExpiry + ")");

            var item = new CacheItem { Expires = utcExpiry, Item = entry };
            var path = GetPathFromKey(key);

            using (var file = File.OpenWrite(path))
            {
                var formatter = new BinaryFormatter();
                formatter.Serialize(file, item);
            }
        }
        private string GetPathFromKey(string key)
        {
            return FilecachePath + MD5(key) + ".txt";
        }

        private string MD5(string s)
        {
            var provider = new MD5CryptoServiceProvider();
            var bytes = Encoding.UTF8.GetBytes(s);
            var builder = new StringBuilder();

            bytes = provider.ComputeHash(bytes);

            foreach (var b in bytes)
                builder.Append(b.ToString("x2").ToLower());

            return builder.ToString();
        }
    }

Step 5 : Now add the class library project reference to your web application and add the following attribute to your web.config file:

  <caching>
      <outputCache defaultProvider="FileCacheProvider">
        <providers>
         <add name="FileCacheProvider" type="CustomCacheProviderLib4_5.FileCacheProvider"/>
        </providers>
      </outputCache>
    </caching>

Step 6: Now add an OutputCache Directive to your page (Default.aspx).

<%@ OutputCache VaryByParam="ID" Duration="300" %>

Step 7: Now run your web application and see that your page is loading from the Cache:



Step 8 : Here is the output window: