In the attempt to simplify the migration from VB6, Microsoft introduced the support for default form instances in VB2005. However, this feature isn’t complete and still creates many problems.
One of such problems is that, even if the code appears to be referencing the same form instance, it actually creates a new form each time the form is shown. To prove this point, consider the following VB.NET code:
Private Sub Form_Load() Handles MyBase.Load
Form2.UserName = "John Doe"
Private Sub Command1_Click() Handles Command1.Click
If you click Command1, then close the second form that appears, and click Command1 again, you will notice that the form’s handle is differente, which in turn proves that you are dealing with two different instances, even though both were accessed through the Form2 variable.
As a consequence for this fact, the second instance of Form2 will have its UserName variable set to an empty string. If your code assumes that the UserName variable value is preserved between calls you are in trouble.
The simplest way to work around this issue is to move the UserName variable into a BAS module (before the migration) or to a VB.NET Module (after the migration), so that its value is preserved between calls.