Sorting gridview bound to datatable in c#.net

Question

I have a gridview which is bound to a DataTable. When I try to sort the gridview, it goes blank. How can I enable sorting this gridview?

I know this question has been asked before, but what I'm looking for is an explanation of how to do it. Perhaps with a simple example.

I have read that I need to put some code in the on_sorting and/or on_sorted events, but I don't understand what needs to go there.

Again, I want to understand the method of accomplishing this, I don't just want a giant block of code.

---

Ok, here's what I have now, but still not working:

            <asp:GridView ID="gridResults" runat="server" CellPadding="4" ForeColor="#333333"
            GridLines="Horizontal" AllowSorting="True" AllowPaging="True" 
            EmptyDataText="No Tracking Information Found for the given criteria." 
            PageSize="15" onsorted="gridResults_Sorted" AutoGenerateColumns="False" 
            EnableSortingAndPagingCallbacks="True">
            <RowStyle BackColor="#E3EAEB" />
            <FooterStyle BackColor="#1C5E55" Font-Bold="True" ForeColor="White" />
            <PagerStyle BackColor="#666666" ForeColor="White" HorizontalAlign="Center" />
            <SelectedRowStyle BackColor="#C5BBAF" Font-Bold="True" ForeColor="#333333" />
            <HeaderStyle BackColor="#1C5E55" Font-Bold="True" ForeColor="White" />
            <EditRowStyle BackColor="#7C6F57" />
            <AlternatingRowStyle BackColor="White" />
        </asp:GridView>

And then in code behind:

  //From search method
gridResults.Columns.Clear();
    foreach (DataColumn col in currentResults.Columns)
    {
        String fieldName = col.ColumnName;
        BoundField field = new BoundField();
        field.DataField = fieldName;
        field.SortExpression = fieldName;
        field.HeaderText = fieldName;

        gridResults.Columns.Add(field);  
    }

    gridResults.DataSource = currentResults;
    gridResults.DataBind();
    gridResults.AllowSorting = true;

Can anyone see what I'm still missing? Results show, but no sorting or paging works.

Answer 1

You are able to make a GridView sortable using a DataTable. All you need to do is make sure that you have Enable Sorting = true and you provide the column name that you wish to be sorted in the SortExpression.

This is what you would need to do to allow this to be sortable:

<asp:BoundField HeaderText="Product" 
      DataField="ProductName" SortExpression="ProductName">
</asp:BoundField>

You always need to set the SortExpression or you are not going to be able to sort your columns