ok, Thanks..
'f1.GetType.ToString' was not working but 'If f1.GetType Is GetType(Form1) Then' is working perfectly..
There's another question I'm not sure:
From frmContainer:
dim f1 as new Form1
f1 .MdiParent = Me
f2.show()
From Form1:
dim f2 as new Form2
f2 .MdiParent = frmContainer.ActiveForm
f2.show()
I hav used this code above, but now I hav noticed that 'frmContainer.ActiveForm' is the same as 'ActiveForm' & it simply refers to the 'Active form' in my Application.
The Active form in my Application is always the 'MDI Container' (frmContainer) since every form I instantiates is a MDIChild of this Container..
But I hav just found another way: f2.MdiParent = Me.ParentForm, Is this one better than the previous?