C Sharp Generic delegates Func, Action and Predicate with anonymous method

Generic delegates in C#: An Overview

In .net 3.5 some new generic delegates -Func<T>, Action<T>, and Predicate<T> were introduced. Using generic delegates, it is possible to concise delegate type which means you don’t have to define the delegate statement. These delegates are the Func<T>, Action<T>, and Predicate<T> delegates and are defined in the System namespace.

In this C# Tutorial, we will explore more about generic delegates which will include generic delegates with examples, func action predicates with examples, and Generic delegates using an anonymous method. Certified C# professionals earn 20% more than non-certified peers. Get your Free C Sharp Course with Certification today!

What are the generic delegates?

• Delegates in C# are nothing but pointers to function.
• They are used for implementing events and call-back methods.
• Func, Action, and Predicate are the delegates defined in C# 3.0
• Func, Action, and Predicate are generic inbuilt delegates.
• Let's see the types of delegates with its example in C# Compiler.

1.Func Delegate in C#:

• Func is a generic delegate present in the System namespace.
• Func takes one or more input parameters and returns one out parameter and the last parameter is considered as a return value.
• It can include 0 to 16 input parameters of different types but it must have one return type.

Example:

Func delegate with two input parameters

 Func func1 = DelegateClass.Add;  
int value = func1(22, 44);  
TParameter = 22,44;  
TOutput = value = 66;    

Func delegate with Anonymous Methods

 Func with Anonymous methods:  
Func func= delegate(intx,int y){ return (x+y); };  
int result = func4(2,3);    

2. Action Delegate in C#

• Action present in the System namespace.
• It takes one or more than one input parameter and returns nothing.
• It does not return any value.

Example:

Action delegate with two input parameters

 Action action1=DelegateClass.ShowEmploye;  
action1(44,"Jayanti");  
TParameter = 44,Jayanti;  
TOutput = Not available (No return value)   

Action delegate with Anonymous Methods

 Action action = delegate(String msg)  
{  
    Console.WriteLine(msg);  
};  
action("Jayanti");     

3. Predicate Delegate in C#

• A predicate delegate is also an inbuilt generic delegate and is present in the System namespace.
• predicate is used to verify certain criteria of the method and returns output as Boolean, either True or False.
• The predicate can be used with the method, anonymous, and lambda expressions.

Example:

Predicate delegate with two input parameters

 Predicate predicate = DelegateClass.IsNumeric;
bool number = predicate("987654");

Predicate delegate with Anonymous Methods

 Predicate predicate = delegate(string str)  
{  
    double retNum;  
    bool isNum = Double.TryParse(Convert.ToString(str), System.Globalization.NumberStyles.Any, System.Globalization.NumberFormatInfo.InvariantInfo, out retNum);  
    return isNum;  
};  
bool found = predicate("987654");   

Generic delegates in a nutshell

Action<T> operates on the generic arguments. Func<T> performs an operation on the argument(s) and returns a value, and Predicate<T> is used to represent a set of criteria and determine if the argument matches the criteria.

 delegate TResult Func  ();
delegate TResult Func  (T arg);
delegate TResult Func  (T1 arg1, T2 arg2);
... up to T16
 delegate void Action ();
delegate void Action  (T arg);
delegate void Action  (T1 arg1, T2 arg2);
... up to T16   

Here "in" shows the input parameters and "out" shows the return value by the delegate.

Read More - C# Interview Questions For Freshers

Generic delegate example

 using System;
class demo 
{ 
delegate void MyDelegate(string str); 
static void Main(string[] args) 
{ 
MyDelegate d = show; 
d("Hello World!"); 
Console.ReadLine();
 }
static void show(string str) 
{ 
Console.WriteLine(str); 
} 
}

The above code can be written using a generic delegate.

 using System;
class demo 
{ 
static void Main(string[] args) 
{ 
Action<string> d = show;
d("Hello World!"); 
Console.ReadLine(); 
}
static void show(string str)
{ 
Console.WriteLine(str); 
} 
}  

Generic delegate using an anonymous method

 using System;
class demo 
{ 
static void Main(string[] args) 
{ 
Action<string> d = s => Console.WriteLine(s); 
d("Hello World!"); 
}
}   

Summary

In this article, I try to explain the generic delegates with examples. I hope after reading this article you will be able to understand the use of generic delegates.

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