DialogResult

Displaying a Windows Form

Dim objMyForm As frmMyForm 

objMyForm = New frmMyForm 
If (objMyForm.ShowDialog = WIndows.Forms.DialogResult.OK) Then 

End If 

DialogResult

This can be used to identify which button was used to close a form.

Private Sub btnStart() Handles btnStart_Click 
   Me.DialogResult = Windows.Forms.DialogResult.OK 
End Sub 

Private Sub btnCancel() Handles btnCancel_Click 
   Me.DialogResult = Windows.Forms.DialogResult.Cancel 
End Sub 

Buttons that return a DialogResult
All buttons have a DialogResult property !!
If you are using the FormClosing event make sure this property is "None" for all buttons.

CancelButton

AcceptButton

If the CancelButton has the focus though pressing Enter will press this button and the AcceptButton is ignored
Always check the TabIndex and make sure this is always the Default OK/Cancel button.

Important

If you change the AcceptButton or the CancelButton property on a windows form the DialogResult property is automatically changed for the button control. If that button is copied and pasted the DialogResult remains intact