c# - Is it possible to "steal" an event handler from one control and give it to another?

Question

I want do something like this:

Button btn1 = new Button();
btn1.Click += new EventHandler(btn1_Click);
Button btn2 = new Button();
// Take whatever event got assigned to btn1 and assign it to btn2.
btn2.Click += btn1.Click; // The compiler says no...

Where btn1_Click is already defined in the class:

void btn1_Click(object sender, EventArgs e)
{
    //
}

This won't compile, of course ("The event 'System.Windows.Forms.Control.Click' can only appear on the left hand side of += or -="). Is there a way to take the event handler from one control and assign it to another at runtime? If that's not possible, is duplicating the event handler and assigning it to another control at runtime doable?

A couple of points: I have googled the heck out of this one for awhile and found no way of doing it yet. Most of the attempted approaches involve reflection, so if you read my question and think the answer is incredibly obvious, please try to compile the code in Visual Studio first. Or if the answer really is incredibly obvious, please feel free to slap me with it. Thanks, I'm really looking forward to seeing if this is possible.

I know I could just do this:

btn2.Click += new EventHandler(btn1_Click);

That's not what I'm looking for here.

This is also not what I'm looking for:

EventHandler handy = new EventHandler(btn1_Click);
Button btn1 = new Button();
btn1.Click += handy;
Button btn2 = new Button();
btn2.Click += handy;

Answer 1

Yeah, it's technically possible. Reflection is required because many of the members are private and internal. Start a new Windows Forms project and add two buttons. Then:

using System;
using System.ComponentModel;
using System.Windows.Forms;
using System.Reflection;

namespace WindowsFormsApplication1 {
  public partial class Form1 : Form {
    public Form1() {
      InitializeComponent();
      button1.Click += new EventHandler(button1_Click);
      // Get secret click event key
      FieldInfo eventClick = typeof(Control).GetField("EventClick", BindingFlags.NonPublic | BindingFlags.Static);
      object secret = eventClick.GetValue(null);
      // Retrieve the click event
      PropertyInfo eventsProp = typeof(Component).GetProperty("Events", BindingFlags.NonPublic | BindingFlags.Instance);
      EventHandlerList events = (EventHandlerList)eventsProp.GetValue(button1, null);
      Delegate click = events[secret];
      // Remove it from button1, add it to button2
      events.RemoveHandler(secret, click);
      events = (EventHandlerList)eventsProp.GetValue(button2, null);
      events.AddHandler(secret, click);
    }

    void button1_Click(object sender, EventArgs e) {
      MessageBox.Show("Yada");
    }
  }
}

If this convinces you that Microsoft tried really hard to prevent your from doing this, you understood the code.