Add and Delete Event in C#

Question

Hello,

I created simple Windows Forms app in C#.
Why is it not possible to remove from the clickMeButton1.Click event?
I expected ClickMeButton1_Click method executed one time because I detach method from event with clickMeButton1.Click -= ClickMeButton1_Click;

The whole project in OneDrive:
https://1drv.ms/u/s!AiKKqJaRZheDognJPo0Ih379wgBQ?e=9qDZVY

namespace WinFormsApp1  
{  
    public partial class Form1 : Form  
    {  
        public Form1()  
        {  
            InitializeComponent();  
        }  
  
        private void Form1_Load(object sender, EventArgs e)  
        {  
            clickMeButton1.Click += ClickMeButton1_Click; //execute   
            clickMeButton1.Click += ClickMeButton1_Click; // execute  
            clickMeButton1.Click += ClickMeButton1_Click; // execute  
        }  
  
        private void ClickMeButton1_Click(object? sender, EventArgs e)  
        {  
            MessageBox.Show("Hi!"); //executed 3 times  
            clickMeButton1.Click -= ClickMeButton1_Click;  
            clickMeButton1.Click -= ClickMeButton1_Click;  
            clickMeButton1.Click -= ClickMeButton1_Click;  
            clickMeButton1.Click -= ClickMeButton1_Click;  
            clickMeButton1.Click -= ClickMeButton1_Click;  
            clickMeButton1.Click -= ClickMeButton1_Click;  
            clickMeButton1.Click -= ClickMeButton1_Click;  
            clickMeButton1.Click -= ClickMeButton1_Click;  
            clickMeButton1.Click -= ClickMeButton1_Click;  
            clickMeButton1.Click -= ClickMeButton1_Click;  
            MessageBox.Show("Bye!"); //executed 3 times  
        }  
    }  
}  

Answer 1

It's expected behavior.

You have assigned the event handler 3 times, right? Then when you click on the button it will run 3 times, no matter what you do inside the event handler.

So it basically does this for 3 times:

• Show Hi
• Remove event handler 10 times
• Show Bye

After completing these 3 rounds, now if you click on the button again, it doesn't run the event handler, because you have removed the event handlers. Well, as a side-note, you don't need to remove the event handler 10 times; 1 time will be enough.

You should not assign the event handler more than once. If you assigned, then you cannot disable it inside the event handler itself, it's too late.