Question

Is it possible to call a delegate stored in a variable by its variable name (as a string)? I guess I’d have to use reflection mechanism, but I’m not getting anywhere

Example code:

class Demo {
  public delegate int DemoDelegate();

  private static int One() {
    return 1;
  }

  private static void CallDelegate(string name) {
    // somehow get the value of the variable with the name
    // stored in "name" and call the delegate using reflection
  }

  private static void CallDelegate(string name, DemoDelegate d) {
    d();
  }

  static void main(string[] args) {
    DemoDelegate one = Demo.One;
    CallDelegate(one);
    // this works, but I want to avoid writing the name of the variable/delegate twice:
    CallDelegate("one", one);
  }

}

Is this even possible? If so how?

Answer 1

Yes, it is possible, as long as you use Linq Expressions, and little reflection.

Take a look at this code, it does something simillar to what I think you want:

using System;
using System.Linq.Expressions;
using System.Reflection;
using System.Collections.Generic;

namespace q6010555
{
    class Demo
    {
        static List<string> varNamesUsed = new List<string>();

        public delegate int DemoDelegate();

        private static int One()
        {
            return 1;
        }
        private static void CallDelegate(Expression<Func<DemoDelegate>> expr)
        {
            var lambda = expr as LambdaExpression;
            var body = lambda.Body;
            var field = body as MemberExpression;
            var name = field.Member.Name;
            var constant = field.Expression as ConstantExpression;
            var value = (DemoDelegate)((field.Member as FieldInfo).GetValue(constant.Value));

            // now you have the variable name... you may use it somehow!
            // You could log the variable name.
            varNamesUsed.Add(name);

            value();
        }
        static void Main(string[] args)
        {
            DemoDelegate one = Demo.One;
            CallDelegate(() => one);

            // show used variable names
            foreach (var item in varNamesUsed)
                Console.WriteLine(item);
            Console.ReadKey();
        }
    }
}