call by name in C#?

Question

Hi everybody.
Can anyone tell me how can I implement Call By Name in C#?
I really have no idea about this.
Thanks for any advise.

Answer 1

You can do that using Reflection:

using System;
using System.Reflection;

class CallMethodByName
{
   string name;

   CallMethodByName (string name)
   {
      this.name = name;
   }

   public void DisplayName()      // method to call by name
   {
      Console.WriteLine (name);   // prove we called it
   }

   static void Main()
   {
      // Instantiate this class
      CallMethodByName cmbn = new CallMethodByName ("CSO");

      // Get the desired method by name: DisplayName
      MethodInfo methodInfo = 
         typeof (CallMethodByName).GetMethod ("DisplayName");

      // Use the instance to call the method without arguments
      methodInfo.Invoke (cmbn, null);
   }
}

Answer 2

If you mean this, then I think the closest equivalent would be delegates.

Answer 3

Pass a lambda function instead of a value. C# is eagerly evaluated so in order to defer execution so that each site re-evaluates the supplied arguments you need to wrap the arguments in a function.

int blah = 1;

void Foo(Func<int> somethingToDo)  {
  int result1 = somethingToDo(); // result1 = 100

  blah = 5;
  int result2 = somethingToDo(); // result = 500
}

Foo(() => blah * 100);

You can use the Lazy class if you're in .NET 4.0 to get a similar (but not identical) effect. Lazy memoizes the result so that repeated accesses do not have to re-evaluate the function.