First of all, we have 2 Windows Form, the main form called Form1, the child form called ChildForm. Add a menu in the main form, use to instantiate the subform, we write down the code in Form1.cs:
Private static childform childform; // static variable, save unique instance
Private void Menuitem2_click (Object Sender, System.Eventargs E)
{
Childform ChildForm = getChildForm (); // Get a child form object
ChildForm.show (); // Display
}
Private child form getChildForm ()
{
// The order cannot be wrong, the previous condition is used to determine if it is the first time, the latter condition is used to determine if the child form is turned off.
IF (ChildForm == Null || CHildForm.Indisposed)
{// The first instantiation is also, it is closed, all re-instantiate
ChildForm = new childform ();
ChildForm.mdiparent = this;
}
Return CHildForm;
}
