Saturday, September 8, 2012

Predicate delegate in C#

I am writing few post on different type of delegates and this post also will be part of it. In this post I am going to write about Predicate delegate which is available from C# 2.0. Following is list of post that I have written about delegates.

  1. Delegates in C#.
  2. Multicast delegates in C#.
  3. Func delegate in C#.
  4. Action delegate in C#.

Predicate delegate in C#:

As per MSDN predicate delegate is a pointer to a function that returns true or false and takes generics types as argument. It contains following signature.

Predicate<T> – where T is any generic type and this delegate will always return Boolean value. The most common use of a predicate delegate is to searching items in array or list. So let’s take a simple example. Following is code for that.

using System;
using System.Collections.Generic;

namespace DelegateExample
    class Program
        static void Main(string[] args)
            Predicate<int> numberGreaterthenFive = i => i > 5;
            List<int> NumberList = new List<int>{1,2,3,4,5,6,7,8,9,10};
            var newlist = NumberList.FindAll(numberGreaterthenFive);
            Action<int> print = i => Console.WriteLine(i);

If you see in the above code I have written a predicate delegate numberGreaterthenFive to decide whether numebr is greater then five or not. Then I have created a list of number and use the predicate delegate which we created just before find that number is greater then five or not. So once we get new list, I have printed the number with console writeline and action delegate.

Let’s run the application and following is output as expected.

Predicate Delegate in C#- Delegate Series

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