MySql Access VB

Question

My application is
Microsoft Access front end
MySql back end
Code is in vb

我正在尝试修改一个包含几个下拉字段的表单[！[在此处输入图像说明] [1]] [1]。在更新之前我需要它来要求 jobcustomerID 。现在，如果我首先添加一个地址，它会告诉我添加客户但是给我一个错误＆＃34;无效使用null＆＃34;

当前代码

    Private Sub Form_BeforeUpdate(Cancel As Integer)
       If IsNull(Me.JobCustomerID) Or Me.JobCustomerID = "" Then
            Call MsgBox("You must select a Customer from the list provided", vbExclamation, "REQUIRED ENTRY")
             Me.JobCustomerID.SetFocus
             Cancel = True
             Exit Sub
           End If
       End Sub

我确实有一个字段的图像，但缺乏所需的声誉

Answer 1

尝试将取消移到前面。

If IsNull(Me.JobCustomerID) Or Me.JobCustomerID = "" Then
    Cancel = True
    MsgBox "You must select a Customer from the list provided", vbExclamation, "REQUIRED ENTRY"
    Me.JobCustomerID.SetFocus
    Exit Sub
End If