把判断放到前面
Dim cb As WinForm.ComboBox = e.Form.Controls("ComboBox1")
If cb.value = "" Then
MessageBox.Show("选择相关表")
Return
End If
Dim tb As Table = Tables("列属性设置_table1")
Dim dtl As DataTable = DataTables("列属性")
Dim dt As DataTable = DataTables(cb.Value) ' 所选择的表
都还没有判断,就使用了,DataTables(cb.Value)肯定会出错了