Question

I have a very simple custom UserControl, named MyControl

In my form I have this code (I tried to put it into LoadEvent and constructor, after InitalizeCompoment):

var crl = new MyControl();
Controls.Add(ctrl);
ctrl.HandleDestroyed+=(sender,evt) => { MessageBox.Show("Destroyed") };

But when I close the form handler is never called.

Answer 1

If it’s on the main form, then I don’t think the event gets called. Try disposing the control in the FormClosing event in order to force the event to be called:

void Form1_FormClosing(object sender, FormClosingEventArgs e) {
  crl.Dispose();
}

Another way is to add the FormClosing event to the UserControl:

void UserControl1_Load(object sender, EventArgs e) {
  this.ParentForm.FormClosing += new FormClosingEventHandler(ParentForm_FormClosing);
}

void ParentForm_FormClosing(object sender, FormClosingEventArgs e) {
  OnHandleDestroyed(new EventArgs());
}

or in Lambda methodology:

void UserControl1_Load(object sender, EventArgs e) {
  this.ParentForm.FormClosing += (s, evt) => { OnHandleDestroyed(new EventArgs()); };
}