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.

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In last few posts about I have written lots of things about delegates and this post is also part of that series. In this post we are going to learn about Action delegates in C#.  Following is a list of post related to delegates.

1. Delegates in C#.
2. Multicast Delegates in C#.
3. Func Delegates in C#.

Action Delegates in c#:

As per MSDN action delegates used to pass a method as parameter without explicitly declaring custom delegates. Action Delegates are used to encapsulate method that does not have return value. C# 4.0 Action delegates have following different variants like following. It can take up to 16 parameters.

• Action – It will be no parameter and does not return any value.
• Action(T)
• Action(T1,T2)
• Action(T1,T2,T3)
• Action(T1,T2,T3,T4)
• Action(T1,T2,T3,T4,T5)
• Action(T1,T2,T3,T4,T5,T6)
• Action(T1,T2,T3,T4,T5,T6,T7)
• Action(T1,T2,T3,T4,T5,T6,T7,T8)
• Action(T1,T2,T3,T4,T5,T6,T7,T8,T9)
• Action(T1,T2,T3,T4,T5,T6,T7,T8,T9,T10)
• Action(T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11)
• Action(T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,T12)
• Action(T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,T12,T13)
• Action(T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,T12,T13,T14)
• Action(T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,T12,T13,T14,T15)
• Action(T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,T12,T13,T14,T15,T16)

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We already know about delegates in C# and I have previously posted about basics of delegates in C#. Following are posts about basic of delegates I have written.

Delegates in C#
Multicast Delegates in C#

In this post we are going to learn about Func Delegates in C#. As per MSDN following is a definition.

“Encapsulates a method that has one parameter and returns a value of the type specified by the TResult parameter.”

Func can handle multiple arguments. The Func delegates is parameterized type. It takes any valid C# type as parameter and you have can multiple parameters as well you have to specify the return type as last parameters.

Followings are some examples of parameters.
Func<int T,out TResult>
Func<int T,int T, out Tresult>

Now let’s take a string concatenation example for that. I am going to create two func delegate which will going to concate two strings and three string. Following is a code for that.

using System;
using System.Collections.Generic;

namespace FuncExample
{
    class Program
    {
        static void Main(string[] args)
        {
            Func<string, string, string> concatTwo = (x, y) => string.Format("{0} {1}",x,y);
            Func<string, string, string, string> concatThree = (x, y, z) => string.Format("{0} {1} {2}", x, y,z);

            Console.WriteLine(concatTwo("Hello", "Jalpesh"));
            Console.WriteLine(concatThree("Hello","Jalpesh","Vadgama"));
            Console.ReadLine();
        }
    }
}

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In yesterday’s post We learn about Delegates and how we can use delegates in C#. In today’s blog post we are going to learn about Multicast delegates.

What is Multicast Delegates?

As we all know we can assign methods as object to delegate and later on we can call that method with the help delegates. We can also assign more then methods to delegates that is called Multicast delegates. It’s provide functionality to execute more then method at a time. It’s maintain delegates as invocation list (linked list).

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I have used delegates in my programming since C# 2.0. But I have seen there are lots of confusion going on with delegates so I have decided to blog about it. In this blog I will explain about delegate basics and use of delegates in C#.

What is delegate?

We can say a delegate is a type safe function pointer which holds methods reference in object. As per MSDN it's a type that references to a method. So you can assign more than one methods to delegates with same parameter and same return type.

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