asp.net gridview paging and sorting with linq to sql custom linq statement

Question

Ok, I know this cant really be that hard, but im having trouble finding any info. I have a gridview on the page that i am filling with data based on a user selected date range(a dropdown list). When the user clicks the button i fill the gridview and display it. This is all done using Linq to Sql. I need to impliment paging and sorting as well. Help PLEASE!!! Below is my button click event... i am open to any suggestions to get this working

protected void btnGenerate_Click(object sender, EventArgs e)
     {
         int dateRange =0;
         if (rbDateList.Checked)
         {
             switch (ddlDateRange.SelectedIndex)
             {
                 case 0:
                     dateRange = 30;
                     break;
                 case 1:
                     dateRange = 60;
                     break;
                 case 2:
                     dateRange = 90;
                     break;
                 default:
                     dateRange = 30;
                     break;
             }
         }
         GYTDataContext gt = new GYTDataContext();
         var productList = from o in gt.PurchaseOrderDetails
                           join p in gt.Products on o.ProductId equals p.ProductId
                           join h in gt.PurchaseOrderHeaders on o.PurchaseOrderId equals h.PurchaseOrderId
                           where h.OrderDate>DateTime.Now.AddDays(-dateRange)
                           group o by o.ProductId into orderedItems
                           select new
                           {
                               orderedItems.Key,
                               QuantityOrdered = orderedItems.Sum(s => s.OrderQuantity)
                           };
         var totalOrderInfo = from p in productList
                              join prod in gt.Products
                              on p.Key equals prod.ProductId
                              select new
                              {
                                  prod.Reference,
                                  UnitPrice = prod.Price,
                                  prod.ManufacturerProductId,
                                  p.QuantityOrdered,
                                  TotalCost = prod.Price * Convert.ToInt32(p.QuantityOrdered)
                              };

        gvOrderReport.DataSource = totalOrderInfo;
         gvOrderReport.DataBind();
         gvOrderReport.Visible = true;

Answer 1

I had the same problem as you. Most examples of linqdatasource, ilustare the WhereParameters > controlparameter functionality which is cool but not that powerful.

The answer is simple: Use a LinqDataSource and just implement the "onselecting" event pass whatever kind of data you wish.

Here is a short example with full filtering-paging-ordering capabilities (also note that the populated sql is optimal and only requests top 10 records every time)

ASPX:

<asp:TextBox ID="txtLastName" runat="server"></asp:TextBox>
<asp:Button ID="btnFilter" runat="server" Text="Filter" 
    onclick="btnFilter_Click"/>

<asp:LinqDataSource ID="LinqDataSource1" runat="server" 
    onselecting="LinqDataSource1_Selecting">
</asp:LinqDataSource>

<asp:GridView ID="GridView1" runat="server" AllowPaging="True" 
    AllowSorting="True" AutoGenerateColumns="False" DataSourceID="LinqDataSource1">
    <Columns>
        <asp:BoundField DataField="FirstName" HeaderText="FirstName" ReadOnly="True" 
            SortExpression="FirstName" />
        <asp:BoundField DataField="MiddleName" HeaderText="MiddleName" ReadOnly="True" 
            SortExpression="MiddleName" />
        <asp:BoundField DataField="LastName" HeaderText="LastName" ReadOnly="True" 
            SortExpression="LastName" />
    </Columns>
</asp:GridView>

CODEBEHIND:

    protected void LinqDataSource1_Selecting(object sender, LinqDataSourceSelectEventArgs e)
    {
        var ctx = new LinqDataSource.DBDataContext();
        IQueryable<Customer> customers = ctx.Customers;

        if (!String.IsNullOrEmpty(txtLastName.Text))
            customers = customers.Where ( c => c.LastName.Contains(txtLastName.Text));

        e.Result = customers;
    }

    protected void btnFilter_Click(object sender, EventArgs e)
    {
        GridView1.DataBind();
    }

Answer 2

Since you are using LINQ-to-SQL with a GYTDataContext, why not use a LinqDataSource to populate your Gridview?

The LinqDataSource can handle paging and sorting automatically.

http://msdn.microsoft.com/en-us/library/bb547113.aspx