Generic Delegates in C#

Before you continue reading this article, you must be familiar with the basics of delegates in C#. If you do not understand delegates then I highly recommend reading this previous article on Delegates.  

• Delegates Simplified by Mahesh Chand

In the preceding article and code sample, we have a delegate called DelegateInt that takes two integer parameters and returns an int type. 

public delegate int DelegateInt(int a, int b);

The DelegateInt works only with methods that have two integer parameters. What if we want to create a delegate that will work with any type of two parameters and return any type? In that case, it will not work. This is where generics are useful and generics play a major role in LINQ.

The following code snippet declares a generic delegate. 

public delegate string GenericDelegateNumber<T1, T2>(T1 a, T2 b);

The following code snippet defines two methods for creating instances of generic delegates. 

public static string AddDoubles(double a, double b)
{
  return (a + b).ToString();
}

public static string AddInt(int a, int b)
{
  return (a + b).ToString();
}

The following code snippet creates two delegate instances where the first one uses integers and the second delegate uses double parameter values. 

GenericDelegateNumber<int, int> gdInt = new GenericDelegateNumber<int, int>(AddInt);
Console.WriteLine(gdInt(3, 6));
GenericDelegateNumber<double, double> gdDouble = new GenericDelegateNumber<double, double>(AddDoubles);
Console.WriteLine(gdDouble(3.2, 6.9));

The following code lists the complete sample. 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace GenericDelegateSample
{
class Program
{
static void Main(string[] args)
{
GenericDelegateNumber<int, int> gdInt = new GenericDelegateNumber<int, int>(AddInt);
Console.WriteLine(gdInt(3, 6));
GenericDelegateNumber<double, double> gdDouble = new GenericDelegateNumber<double, double>(AddDoubles);
Console.WriteLine(gdDouble(3.2, 6.9));
Console.ReadKey();
}

// Generic Delegate takes generic types and returns a string
public delegate string GenericDelegateNumber<T1, T2>(T1 a, T2 b);

public static string AddDoubles(double a, double b)
{
return (a + b).ToString();
}

public static string AddInt(int a, int b)
{
return (a + b).ToString();
}
}

}