How to control MDI forms through a general method?

Question

I am developing a system with MDI forms. I have a menu that is the MdiParent and everyone else is allocated as your children.

Originally, MDI allowed me to open the same form several times; then I started to control the existence of the forms through a static statement, thus:

public static Form form1;

When opening the form:

if (form1 != null)
{
    form1.Activate();
}
else
{
    form1 = new TED_Dados();
    form1.MdiParent = this;
    form1.Show();
}

And finally, when I close the form:

Menu.form1 = null;

This code is functional, but it is necessary to replicate it to all forms, and I need all of them to be declared in the menu. I would like to know if there is any solution that would allow me to control all forms through a single class or method.

Answer 1

There are several ways to solve this.

One approach I like is to create a generic method to open the Forms.

In this case, the method is in the MDI form.

public void OpenForm<TForm>() where TForm : Form, new()
{
    var form = Application.OpenForms.OfType<TForm>().FirstOrDefault();
    if (form != null)
        form.BringToFront();
    else
        new TForm {MdiParent = this}.Show();
}

See a working GIF: