Asp.net 使用对象声明dataview

我在前面的代码中有一个对象，它绑定在datagrid上。现在我需要添加排序列。我搜索web以从数据源转换数据表。但我得到一个错误“必须在使用DataView之前设置DataTable” 有人告诉我怎么做吗？提前谢谢

下面是绑定datagrid的代码：

Dim thisOrder as New co.Orders(123)
dgrdOrders.DataSource=thisOrder
dgrdOrders.DataBind()

这是我的代码：

Private Sub dgrdOrders_SortCommand(source As Object, e As DataGridSortCommandEventArgs) Handles dgrdOrders.SortCommand        

    Dim dataTable As DataTable = TryCast(dgrdOrders.DataSource, DataTable)
    Dim dv As New DataView(dataTable)
    dv.Sort = e.SortExpression
    dgrdOrders.DataSource = dv
    dgrdOrders.DataBind()
End Sub

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最后我找到了排序的方法：

  Private Sub dgrdOrders_SortCommand(source As Object, e As DataGridSortCommandEventArgs) Handles dgrdOrders.SortCommand

    Dim lstOrders As New List(Of co.Order)
      For Each objOrder As co.Order In thisOrder
        lstOrders.Add(objOrder)
      Next

    Select Case e.SortExpression
       Case "Type"
          lstOrders  = lstOrders.OrderBy(Function(x) x.Type).ToList
       Case "Region"
          lstOrders  = lstOrders.OrderBy(Function(x) x.Region).ToList
     End Select
     dgrdOrders.DataSource = lstOrders  
     dgrdOrders.DataBind()

   End Sub