This is an extension of my earlier blog post. I myself, find delegates as one of the most powerful type to use in C#. It helps in writing very flexible and scalable program.
As 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 is provided.
One more type of predefined delegate that is provided by .NET that is counterpart Action delegate . As we saw that it always returns void. But Func returns a value instead of void as Action does.
There is also 5 flavours of the Func delegate is provided.These are
– Public delegate TResult Func<TResult>()
— Public delegate TResult Func<TResult>() // Take no parameter and returns a value
– Public delegate TResult Func<T, TResult>(T t) // Take one input parameter and returns a value
– Public delegate TResult Func<T1, T2, TResult>(T1 t1, T2 t2) // Take 2 input parameter and returns a value
– Public delegate TResult Func<T1, T2, T3, TResult>(T1 t1, T2 t2, T3 t3) // Take 3 input parameter and returns a value
– Public delegate TResult Func<T1, T2, T3, T4, TResult>(T1 t1, T2 t2, T3 t3,T4 t4) // Take 4 input parameter and returns a value
If we see the declaration, TResult is put at last, this is just a convention. One can put it wherever s/he wants.
First lets 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 lets move to code to another overload of Func Delegate. It takes two input parameter and resturns 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 same as Action delegate. i e It can also be used with Anonymous functions and Lambda functions. Lets have a quick look on 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 must have 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 few weeks back, I found it very useful. It helps us writing better and well organised code, also less error prone code. I talked to lot of developers, they didn’t have any idea about these predefined delegates. So I thought of sharing to you all.
Please share your valuable feedback.
Cheers,
Brij
Code Wala 