C# has an interesting delegate option, Func. Func is nothing but a syntactic sugar over classic delegate template, but it does make it simple to process and to read. If we have the following code using delegate

static int Factorial(int source)
        {
            int first=1;
            for (int i=1;i<=source;i++)
            {
                first*=i;
            }
            return first;
        }
delegate T SingleMath<T,T1>(T1 arg);
SingleMath<int,int> singleMath=Factorial;
Code language: C# (cs)

We can also write the same exact thing using Func:

static int Factorial(int source)
        {
            int first=1;
            for (int i=1;i<=source;i++)
            {
                first*=i;
            }
            return first;
        }
Func<int,int> mathFunc=Factorial;
Code language: C# (cs)

This is both clearer and shorter. we can pass a value of this delegate the same way:

static int DoSomething(int source,Func<int,int>)
        {
            
        }
Code language: C# (cs)

This can be used in functional programming schema. Templates can also be used in a template based as well:

static int DoSomething(int source,Func<T,T1>)
        {
            
        }
Code language: C# (cs)

In the example above, T1 and T can be different or the same parameter types.