C#

e.Handled = (txtKod.Text.Length == 3);

Adriaan Davel wrote:

I would hate to have to code for each vendor

public override void Test(int arg) {
    using (Form f=new Form()) {
        f.Text="my latest form";
        f.Show();
        listForms("Form shown");
        f.Hide();
        listForms("Form hidden");
        // f.Close();                     // optional
        // listForms("Form closed");      //
    }
    GC.Collect();
    listForms("Collected");
}

private void listForms(string title) {
    log("List of forms: "+title);
    int i=0;
    foreach (Form f in Application.OpenForms) {
        log("    Form "+i+" text="+f.Text);
        i++;
    }
    log("Found "+i+" forms");
}

Roger Wright wrote:

an article that explained that if Close() is called on a hidden Form, it doesn't work, nor does it emit an error. At least, not reliably