主题：[新手求教]说明书这段如何在找不到表和列时不报错啊？

可视化授权的实现

For Each t As Table In Tables
    t.Visible = True
    t.AllowEdit = true
    For Each c As Col In t.Cols
        c.Visible = True
        c.AllowEdit = True
    Next
Next
Tables("授权表").Visible = (User.Type <> UserTypeEnum.User )
If User.Type = UserTypeEnum.User Then
    For Each dr As DataRow In DataTables("授权表").Select("分组名 = '" & User.Group & "'" )
        If dr.IsNull("列名") Then
            Tables(dr("表名")).Visible = Not dr("不可见")
            Tables(dr("表名")).AllowEdit = Not dr("不可编辑")
        Else
            Tables(dr("表名")).Cols(dr("列名")).Visible = Not dr("不可见")
            Tables(dr("表名")).Cols(dr("列名")).AllowEdit = Not dr("不可编辑")
        End If
    Next
End If

这段代码， 要是在某个用户的客户端没有载入某表某列， 然后授权表中又说到那表那列时， 就会报错。

如何简单修改下让其跳过找不到的表和列啊，然后其它行照样生效啊？

For Each t As Table In Tables
    t.Visible = True
    t.AllowEdit = True
    For Each c As Col In t.Cols
        c.Visible = True
        c.AllowEdit = True
    Next
Next
Tables("授权表").Visible = (User.Type <> UserTypeEnum.User )
If User.Type = UserTypeEnum.User Then
    For Each dr As DataRow In DataTables("授权表").Select("分组名 = '" & User.Group & "'" )
        If Tables.Contains(dr("表名")) Then
            If dr.IsNull("列名") Then
                Tables(dr("表名")).Visible = Not dr("不可见")
                Tables(dr("表名")).AllowEdit = Not dr("不可编辑")
            Else
                If  Tables(dr("表名")).Cols.Contains(dr("列名")) Then
                    Tables(dr("表名")).Cols(dr("列名")).Visible = Not dr("不可见")
                    Tables(dr("表名")).Cols(dr("列名")).AllowEdit = Not dr("不可编辑")
                End If
            End If
        End If
    Next
End If