C# – How to Disable Alt + F4 closing form


What is the best way to disable Alt + F4 in a c# win form to prevent the user from closing the form?

I am using a form as a popup dialog to display a progress bar and I do not want the user to be able to close it.

Best Solution

This does the job:

private void Form1_FormClosing(object sender, FormClosingEventArgs e)
    e.Cancel = true;

Edit: In response to pix0rs concern - yes you are correct that you will not be able to programatically close the app. However, you can simply remove the event handler for the form_closing event before closing the form:

this.FormClosing -= new System.Windows.Forms.FormClosingEventHandler(this.Form1_FormClosing);