Question

I am trying to sort a gridview in visual basic using the following method, however the second line of code (Dim dv as DataView…) throws a NullReferenceException. When I debug the code and step through it, I can see that the DataTable dt has a value of “Nothing” after it is instantiated. Any help would be greatly appreciated.

        Dim dt As DataTable = grdExpProd.DataSource
        Dim dv As DataView = dt.DefaultView

        If (blnExTraining) Then
            dv.Sort = "ExpirationDate DESC"
        Else
            dv.Sort = "ExpirationDate ASC"
        End If

        grdExpProd.DataSource = dv
        grdExpProd.DataBind()

Answer 1

After postback the DataSource of any Web-Databound-Control like GridView is Nothing (null in C#). Note that HTTP is stateless, all objects that are created in a page’s life-cycle will be destroyed as soon as the page was rendered.

So the solution is easy, select the DataSource again with the correct ORDER BY.