Explanation of Func

Question

I was wondering if someone could explain what Func is and how it is used with some clear examples.

Answer 1

A Func eats ints and returns strings. So, what eats ints and returns strings? How about this ...

public string IntAsString( int i )
{
  return i.ToString();
}

There, I just made up a function that eats ints and returns strings. How would I use it?

var lst = new List() { 1, 2, 3, 4, 5 };
string str = String.Empty;

foreach( int i in lst )
{
  str += IntAsString(i);
}

// str will be "12345"

Not very sexy, I know, but that's the simple idea that a lot of tricks are based upon. Now, let's use a Func instead.

Func fnc = IntAsString;

foreach (int i in lst)
{
  str += fnc(i);
}

// str will be "1234512345" assuming we have same str as before

Instead of calling IntAsString on each member, I created a reference to it called fnc (these references to methods are called delegates) and used that instead. (Remember fnc eats ints and returns strings).

This example is not very sexy, but a ton of the clever stuff you will see is based on the simple idea of functions, delegates and extension methods.

One of the best primers on this stuff I've seen is here. He's got a lot more real examples. :)