How to limit the number of open forms?

Question

I have a Main form, which is MDI, and it has many child forms.

I want to limit the number of forms that can be open at once - e.g. no more than 8 forms open at a time.

How can I accomplish this?

Answer 1

If you're using MDI properly, then just check the Length of the MdiChildren collection in the Main MDI Form:

private void button1_Click(object sender, EventArgs e)
{
    if (this.MdiChildren.Length < 8)
    {
        Form child = new Form();
        child.MdiParent = this;
        child.Show();
    }
}