函式 'Instance' 並未傳回有關所有程式碼路徑的值。使用該結果時,可能會在執行階段發生 null 參考例外狀況。
VB.NET code
 Private frm1 As Form_customer_order
    Public Function Instance(ByVal frm As Form_customer_order)
        frm1 = frm
    End Function
------解决方案-------------------- Private frm1 As Form_customer_order=Nothing
   Public Function Instance(ByVal frm As Form_customer_order)
       frm1 = frm
   End Function