Based on Microsoft definition "Func is a generic delegate that encapsulates a method that can accept parameters and return some value." There is about 17 override for Func in Dot Net. Here is the different declaration of Func delegate in C#:
public delegate TResult Func<out TResult>() public delegate TResult Func<in T, out TResult>(T arg); public delegate TResult Func<in T1, in T2, out TResult>(T1 arg1, T2 arg2); public delegate TResult Func<in T1, in T2, in T3, out TResult>(T1 arg1, T2 arg2, T3 arg3); … public delegate TResult Func<in T1, in T2, in T3, in T4, in T5, in T6, in T7, in T8, in T9, in T10, in T11, in T12, in T13, in T14, in T15, in T16, out TResult>(T1 arg1, T2 arg2, T3 arg3, T4 arg4, T5 arg5, T6 arg6, T7 arg7, T8 arg8, T9 arg9, T10 arg10, T11 arg11, T12 arg12, T13 arg13, T14 arg14, T15 arg15, T16 arg16);
As you can see The first delegate cannot accept parameters and return Type that is specified by the TResult parameter. For example:
Func<double> func = () => Math.PI / 3;
Or
Func<int, string> func = (x) => string.Format("value={0}", x);
These samples are the usage Fun with Lambda Expression. Rather than Lambda Expression, Fun provides a way to store anonymous methods in a generalized way. For example:
public static string Sum(int a, int b)
{
string result = string.Format("Sum:{0}", a + b);
return result;
}
static void Main(string[] args)
{
Func<int, int, string> func = Sum;
string result = func(4, 5);
Console.WriteLine(result);
}
Finally, Fun can be used as anonymous functions:
static void Main(string[] args)
{
Func<int, int, string> func3 = delegate (int a, int b)
{
string result3 = string.Format("Sum:{0}", a + b);
return result3;
};
string result = func3(4, 5);
Console.WriteLine(result);
}