What is the best or most interesting use of Extension Methods you've seen? [closed]

Answer 1

Often times, I've needed to display a user-friendly value based on an Enum value, but didn't want to go the custom Attribute route, as it didn't seem too elegant.

With this handy extension method:

public static string EnumValue(this MyEnum e) {
    switch (e) {
        case MyEnum.First:
            return "First Friendly Value";
        case MyEnum.Second:
            return "Second Friendly Value";
        case MyEnum.Third:
            return "Third Friendly Value";
    }
    return "Horrible Failure!!";
}

I can do this:

Console.WriteLine(MyEnum.First.EnumValue());

Yay!