MDI childs - can't make active no matter what i try

[ferguslogic]

Hello everyone,

I have a C# winforms application which is designed as a mdi application.
I am having a focus problem with it that I cannot seem to solve.

If I open a mdi child and it is the only child form that is open in the mdi parent then the focus sets to this mdi child without issue and the cursor appears in the text field with the tab index of 0 exactly as it should.

However, if I open up a mdi child form and another mdi child form is already open in the mdi parent, then the mdi chid becomes active (the title bar is bright blue as if it is active) but the cursor stays on the first mdi child window. So if I hit the tab key even though the back window does not have focus, the controls in the back window are being tabbed through rather than the front window with focus.

I thought that it might relate to how I was displaying the mdi child so I have tried all of these options include many variations of sequence
frmPOS.TopMost = true;
frmPOS.Show();
frmPOS.Activate();
frmPOS.Focus();
frmPOS.BringToFront();
frmPOS.Refresh();
frmPOS.Select();
frmPOS.Update();

No matter what I do, the cursor will not appear in the mdi child that i display if at least 1 mdi child is already on the screen.

Any ideas?

[ferguslogic]

Well I answered my own question and I hope that this helps someon else out.

I bet this is causing 99% of the mdi child focus problems that everyone is experiencing when you search on google, msdn or here on these boards.

The problem with my mdi child focus issue was being caused by the way i was firing and handling events or by the way .net handles this functionality.

In my application, a modal dialog was being displayed so that users could type in employee numbers before opening a mdi child screen (for security purposes).

This box was firing events of loginSucceeded and loginFailed and the event handlers would then close the modal login screen and show the correct mdi child form.

You would think this would work but when stepping through the code i noticed that irregardless as to whether I closed the modal form or not, .net was still returning focus back to it to finish out the sub procedure after the event fired and this was pulling focus away from my mdi child forms.


So i removed the event functionality and used the DialogResult returned from the modal dialog instead which ensured that this window was closed prior to showing the mdi child and that resolved the issue.

If you are having mdi child focus issues, step through the code with f10 and see if focus is being set somewhere else after your mdichild is displayeyed.

8 )

hope that helps someone.