Preventing Multiples of an MDI Child Form

I ran into an issue with my C# development, in the mdi-child forms being allowed to be opened multiple times. Which for the application I am developing at the moment, is not a good thing.

Having multiples of the same form was confusing some database filtering for other forms.

Having had this issue back in Delphi 3, I racked my brain trying to figure out how to stop this happening in Visual Studio 2012 using C#.

The code below will hopefully be of some help to you, I found many solutions online and some just made things even more confusing.

The code sample below, is in my view the easiest to follow. As you can see, it’s in a Button_Click() method, but it could be anywhere. To adapt to suit your own needs. Simply change (f.Text == “Client Record Manager”) to suite the Text property of your own form, and replace ClientsFrm with the name of your form.

[code lang=”csharp”]private void ClientsBtn_Click(object sender, EventArgs e)
bool IsOpen = false;
foreach (Form f in Application.OpenForms)
if (f.Text == “Client Record Manager”)
IsOpen = true;
f.WindowState = FormWindowState.Normal;

if (IsOpen == false)
ClientsFrm ClientsFrm = new ClientsFrm();
ClientsFrm.MdiParent = this;

Leave a Reply

%d bloggers like this: