Pass a derived class, to a method that takes the base Class

[HBMSGuy]

Hi, I have a question regarding Methods.
I have a method that takes a base class. I am getting an Error when I pass class that is derived of the base to it.
For Example

Class TaskToRun
{
public virtual void run ();
}

Class SayHi : TaskToRun
{
public run()
{
Console.WriteLine("Hi");
}

Now I can't pass SayHi to a method that takes TaskToRun as its parameter:

RunTask(TaskToRun task)
{
delegate void MethodToRun();
MethodToRun methodtorun = new MethodToRun(task.run);
methodtorun();
}

Thank you so much for any help!

[Antenka]

Hello, HBMSGuy.
Are you sure, that you have error about passing derived class when method asks the base one? Only thing, that I see it's a few mistakes (in other area):

Class TaskToRun
{
     public virtual void run ();
}

here if you don't specify any functionality to the method 'run', call the calss (also as this method) as abstract. Or add empty brackets pair: { } - if you want to leave it as virtual.

Class SayHi : TaskToRun
{
    public run()
    {
        Console.WriteLine("Hi");
    }
}

if you decided to make your base class abstract, you should add 'override' keyword to method run . Also the return type is also needed :P
if you decided to leave your method in base class as virtual - you have 2 ways to go:

Warning 'SayHi.run()' hides inherited member 'TaskToRun.run()'. To make the current member override that implementation, add the override keyword. Otherwise add the new keyword.

RunTask(TaskToRun task)
{
   delegate void MethodToRun();
   MethodToRun methodtorun = new MethodToRun(task.run);
   methodtorun();
}

The delegate declaration should be at class level (like you would declare variable in the class) .. or higher - in namespace. You decide.
Also there're some notes about initializing and calling it. Look here, there is good example: delegate (C# Reference).

Well, here's what we have in result (my version):

delegate void MethodToRun();

class TaskToRun
    {
        public virtual void run() { }
    }

class SayHi : TaskToRun
    {
        public override void run()
        {
            Console.WriteLine("Hi");
        }
    }
public class Test
    {        
        void RunTask(TaskToRun task)
        {
            MethodToRun methodtorun = task.run;
            methodtorun();

        }
        static void Main()
        {
             RunTask(new SayHi());
        }
    }

[HBMSGuy]

Thank you so much. I think your first idea was what I was looking for.
You were correct, how I was trying to complete the task was wrong.

[HBMSGuy]

OK. I thought that was my issue, but it wasn't. :(
Sorry there is a lot of code.

using System;
using System.ComponentModel;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;

namespace Trajectory
{
    abstract class TaskToRun
    {
        public abstract void run();
    }
    class ProjectilePath : TaskToRun
    {   //This will contain the data for each one of the launchers combinations
        //Many Varibles
        public override void run()
        {
            Console.WriteLine("Running in background");
        }
    }
    class Threads
    {   //Will help create and manage the threads that are to be used by the program
        private TaskToRun[] dervivedobject;
        private delegate void MethodToRun();
        private MethodToRun[] methodtorun;
        public Threads(ref TaskToRun[] in_derivedobject)
        {
            this.dervivedobject = in_derivedobject;
            //Initilize the Array of Delegates
            Array.Resize(ref this.methodtorun, (int)this.numberoftasks_backing);
            for (int index = 0; index < this.derivedobject.Length; index++)
            {
                methodtorun[index] = new MethodToRun((dervivedobject[index]).run);
                Console.WriteLine("Added method to methodtorun[{1}]", index);
            }
        }
        //Other Methods
    }
    class Test
    {
        public static void Main()
        {
        ProjectilePath[] arrayoftasks = new ProjectilePath[50];
        Threads treads = new Threads(arrayoftasks);
        }
    }
}

Thanks so much.