CountBy, a new LINQ function introduced in.NET 9, simplifies common data grouping and counting operations. By effectively classifying elements according to a given key, this function generates a collection of KeyValuePair objects. Every key-value pair denotes a group and the number of elements that go with it. Before.NET 9, we had to use a two-step procedure to group elements and count how often they appeared. First, we categorized elements according to a particular key using the GroupBy technique. We then projected each group in order to determine how many elements it contained.

Example
var message = "welcometoprpcoding";
var characterOccurences = message
                            .GroupBy(c => c)
                            .Select(g => new { Key = g.Key, Value = g.Count() });

foreach (var characterOccurence in characterOccurences)
{
    Console.WriteLine($"Character: {characterOccurence.Key}, " +
                      $"Count: {characterOccurence.Value}");
}

Grouping and Counting Characters
This code uses LINQ to group the characters in the string and count their occurrences.

  • message.GroupBy(c => c): Groups the characters based on their value. Each group contains characters with the same value.
  • Select(g => new { Key = g.Key, Value = g.Count() }): Projects each group into an anonymous object with two properties:
    • Key: The character itself.
    • Value: The count of occurrences of that character in the group.

Output

With .NET 9, the CountBy method significantly streamlines this process.
var message = "welcometoprpcoding";
var characterOccurences = message.CountBy(c => c);

foreach (var characterOccurence in characterOccurences)
{
    Console.WriteLine($"Character: {characterOccurence.Key}, " +
                      $"Count: {characterOccurence.Value}");
}

Output

Key Benefits of CountBy

  • Conciseness: Simplifies code, improving readability.
  • Efficiency: Potentially optimizes performance by streamlining the grouping and counting process.
  • Clarity: Clearly expresses the intent of categorizing and quantifying elements.

By leveraging the CountBy method, you can write more concise, efficient, and expressive LINQ queries in your .NET 9 applications. Happy Coding!

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