How to avoid Multiple Child forms shown in MDIParent C# Win Forms

Question

I want to avoid my child form from appearing many times when a user tries to open the child form which is already open in MDIParent. One way to avoid this is by disabling the Controller (in my case BUTTON) but I have given a shortcut key (Ctrl+L) for this function as well. So if the user types Ctrl+L, the same child Form opens and I can see two child forms are in MDI.

private void leadsToolStripMenuItem_Click(object sender, EventArgs e)
    {
        frmWebLeads formWeblead = new frmWebLeads();
        formWeblead.MdiParent = this;
        formWeblead.WindowState = System.Windows.Forms.FormWindowState.Maximized;
        formWeblead.Show();

    }

I want to avoid this. How can I do this?

In the image you can see that a child form Name Online Leads is opened twice as the user opened first time using Menu (LEADS) and second time by Shortcut key. I don't want this to happen. If the form is already opened it should avoid opening another same form ... How to do this?

Answer 1

the way i usually do it if i am only supposed to have one open is something like:

//class member for the only formWeblead
frmWebLeads formWebLead = null;

private void leadsToolStripMenuItem_Click(object sender, EventArgs e)
{
    if (formWebLead == null)
    {
        formWeblead = new frmWebLeads();
        formWeblead.MdiParent = this;
    }

    formWeblead.WindowState = System.Windows.Forms.FormWindowState.Maximized;
    formWeblead.Show();
}