VB.Net SelectedChangeCommitted抛出错误

Question

我真的很恼火在这里。我不明白为什么这个事件不断抛出一个空白的错误。以下是我的代码。

Private Sub cboSections_SelectedChangeCommitted(sender As System.Object, e As System.EventArgs) Handles cboSections.SelectionChangeCommitted 
    On Error GoTo EH 

    If TypeOf sender Is Windows.Forms.ComboBox Then 
     'some boolean that checks if we are skipping this event, thus it does if so 
     If mbSkipEvent Then Exit Sub 

     'checks if index that was changed to is > 0 then it toggles the bottom command buttons 
     If cboSections.SelectedIndex > 0 Then 
      ToggleCmdButtons(True) 
     Else 
      ToggleCmdButtons(False) 
     End If 

     'sets the string msPurpose 
     msPurpose = "Show Section" 
     Debug.Print("Im here") 
    End If 
EH: 
    Debug.Print("Error Description: " & Err.Description) 
End Sub 

在我的输出中，我得到“错误描述：”。而已。如果任何人有任何解决方案或指向正确的方向将是伟大的。

Answer 1

让我们尝试一些真正的错误处理，看看你是否有更好的。虽然我们在这，但我们可以简化代码：

Private Sub cboSections_SelectedChangeCommitted(sender As System.Object, e As System.EventArgs) Handles cboSections.SelectionChangeCommitted 
    Dim comboBox = TryCast(sender, ComboBox) 
    If comboBox Is Nothing OrElse mbSkipEvent Then Exit Sub 
    Try 
     'checks if index that was changed to is > 0 then it toggles the bottom command buttons 
     ToggleCmdButtons(cboSections.SelectedIndex > 0) 

     'sets the string msPurpose 
     msPurpose = "Show Section" 
     Debug.Print("Im here") 
    Catch Ex As Exception 
     Debug.Print("Error Description: " & Ex.Message) 
    End Try 
End Sub