Looking in Func Delegates

This is an extension of my earlier blog post. I myself, find delegates as one of the most powerful types to use in C#. It helps in writing very flexible and scalable programs.

I already discussed in my last blog that in the traditional way, we need to write more code. There I also discussed, one predefined delegate Action delegate that is provided by the framework. There are four flavors of Action delegate provided.

One more type of predefined delegate that is provided by .NET is the counterpart Action delegate. As we saw, it always returns void. But Func returns a value instead of void as Action does.

There are also 5 flavours of the Func delegate that are provided. These are:

Public delegate TResult Func<TResult>()

• C#

  Public delegate TResult Func<TResult>()  // Take no parameter and return a value

• C#

  Public delegate TResult Func<T, TResult>(T t)  // Take one input parameter 
  					 // and return a value

• C#

  Public delegate TResult Func<T1, T2, TResult>(T1 t1, T2 t2)  // Take 2 input 
  					// parameters and return a value

• C#

  Public delegate TResult Func<T1, T2, T3, TResult>(T1 t1, T2 t2, T3 t3)  // Take 3 
  					// input parameter and return a value

• C#

  Public delegate TResult Func<T1, T2, T3, T4, TResult>
      (T1 t1, T2 t2, T3 t3,T4 t4)  // Take 4 input parameter and return a value

If we see the declaration, TResult is put last, this is just a convention. One can put it wherever s/he wants.

First let's see first one, with no parameter and returning a value:

public class Program
{
static void Main(string[] args)
{
//Creating the Func variable and assigning it a function
Func<string> myFunc = SayHello;

//Calling function using Func Delegate
string returnedString = myFunc();

Console.WriteLine(returnedString);

Console.ReadKey();
}

private static string SayHello()
{
return "Hello Dude!!";
}
}

Now let's move to code to another overload of Func Delegate. It takes two input parameters and returns a value.

public class Program
{
static void Main(string[] args)
{
//Creating the Func variable (which takes two input parameters and returns a value) 
//and assigning it a function
Func<double, double, double> myFunc1 = Add;

//Calling function using Func Delegate
double sum = myFunc1(3.5, 4.5);

Console.WriteLine(sum);

Console.ReadKey();
}

private static double Add(double first, double second)
{
return first + second;
}
}

It is also the same as Action delegate, i.e., it can also be used with Anonymous functions and Lambda functions. Let's have a quick look at both:

Anonymous Function

public class Program
{
static void Main(string[] args)
{
//Creating the Func variable (which takes three input parameters and returns a value) 
//and assigning it an Anonyomus function
Func<double, double, double, double> myFunc1 = delegate(double d1, double d2, double d3)
{
return d1 + d2 + d3;
};

//Calling function using Func Delegate
double sum = myFunc1(3.5, 4.5, 5.5);

Console.WriteLine(sum);

Console.ReadKey();
}
}

Lambda Function

public class Employee
{
public int Id { get; set; }
public string Name { get; set; }
}
public class Program
{
static void Main(string[] args)
{

Func<Employee,string> checkEmployee = s=>{
if (s.Id > 11)
return s.Name;
else
return "Employee is not with the given Criteria.";
};

Console.WriteLine(checkEmployee(new Employee() {Id=12, Name="Brij"}));
Console.WriteLine(checkEmployee(new Employee() {Id=10, Name="Abhijit"}));

Console.ReadKey();
}
}

Hope you all enjoyed the delegates.

We use delegates a lot. But most of us use the traditional way in programs. When I learnt first these Action and Func delegates a few weeks ago, I found them very useful. It helps us in writing better and well organised code, which is also less error prone. I talked to a lot of developers, they didn’t have any idea about these predefined delegates. So I thought of sharing with all of you.

Please share your valuable feedback.

Cheers,

Brij