LINQ

//1
delegate void FunctionPointer(string str);
static void Main(string[] args)
{
    FunctionPointer fp = HelloWorld;
    fp("Hello World");
}

static void HelloWorld(string str)
{
    Console.WriteLine(str);
    Console.ReadLine();
}
//2
delegate void FunctionPointer(string str);
static void Main(string[] args)
{
    FunctionPointer fp = delegate(string s)
    {
        Console.WriteLine(s);
        Console.ReadLine();
    };
    fp("Hello World!");
}
//3
delegate void FunctionPointer(string str);
static void Main(string[] args)
{
    FunctionPointer fp = a => Console.WriteLine(a);

    fp("Hello World");
    Console.ReadLine();
}
//4
static void Main(string[] args)
{
    Action<string> fp = s => Console.WriteLine(s);
    fp("Hello World!");
    Console.ReadLine();
}