如何在属性方法VB.NET中使用GridViewUpdateEventArgs

Question

I wanna show drop down list on the footer of my GridView.

    aspx code:
 <FooterTemplate>                                                      
 <asp:DropDownList ID="ddSrc" runat="server">    
 </asp:DropDownList>                                                   
 </FooterTemplate>



 'VB Code
         Protected Sub gvID_RowDataBound(sender As Object, e As GridViewRowEventArgs)
             If e.Row.RowType = DataControlRowType.DataRow Then
                 If e.Row.DataItem IsNot Nothing Then
                    Dim ddSrc As DropDownList = DirectCast(e.Row.FindControl("ddSrc"), DropDownList)      
                        If ddSrc IsNot Nothing Then
                             ddSrc.DataTextField = "Name"
                             ddSrc.DataValueField = "Id"
                             ddSrc.DataSource = GetData()
                             ddSrc.DataBind()
                        End If
                 End If
             End If
         End Sub

I have used above code behind code used to load my dropdown list but getting issue like "object reference not set to an instance of an object " over the line " ddSrc.DataTextField = "Name" " during runtime.

I have edited my question to easy understand.

Answer 1

you need to load droupdown list on RowDataBound event of grid view

Protected Sub gvID_RowDataBound(sender As Object, e As GridViewRowEventArgs)
    If e.Row.RowType = DataControlRowType.Footer Then
        If e.Row.DataItem IsNot Nothing Then
           Dim ddSrc As DropDownList = DirectCast(e.Row.FindControl("ddSrc"), DropDownList)      
               If ddSrc IsNot Nothing Then
                    ddSrc.DataTextField = "Name"
                    ddSrc.DataValueField = "Id"
                    ddSrc.DataSource = GetData()
                    ddSrc.DataBind()
               End If
        End If
    End If
End Sub

Answer 2

Shot in the dark, but could it mean it requires a 'new' in the declaration?

Dim e As New GridViewUpdateEventArgs 

If it hasnt been created yet, you wont be able to assign a variable to it.