c# - allow sorting by column gridview

Question

I am writing project which gets data from Data Acess Layer and show it in GridView. The problem is to allow sorting by column. When I click on head of columnt following occurs following error:

Exception Details: System.Web.HttpException: GridView 'GridView1' Trigger Events Sorting, which has not been processed.

Here the .cs code:

public partial class Default: System.Web.UI.Page
    {
        EmployeesTableAdapter eta = new EmployeesTableAdapter();

        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                GridView1.DataSource = eta.GetData();
                GridView1.DataBind();
            }
        }
    }

Here the .aspx code(only gridview):

<asp:GridView ID="GridView1" runat="server" AllowPaging="True" 
        AllowSorting="True" CellPadding="4" ForeColor="#333333" GridLines="None" 
        AutoGenerateColumns="False">
        <AlternatingRowStyle BackColor="White" />

<Columns>
            <asp:TemplateField HeaderText="Select">
                <ItemTemplate>                
                    <asp:CheckBox ID="CheckBox1" runat="server">
                </asp:CheckBox>
                </ItemTemplate>                
            </asp:TemplateField>  

            <asp:BoundField DataField="FirstName" HeaderText="FirstName" SortExpression="FirstName" />
            <asp:BoundField DataField="LastName" HeaderText="LastName" SortExpression="LastName" />
            <asp:BoundField DataField="Country" HeaderText="Country" SortExpression="Country" />

            <asp:TemplateField HeaderText="View">
                <ItemTemplate>                
                    <asp:ImageButton ID="ImageButton1" runat="server" ImageUrl="images/view.png"/>
                </ItemTemplate>                
            </asp:TemplateField> 

            <asp:TemplateField HeaderText="Edit">
                <ItemTemplate>                
                    <asp:ImageButton ID="ImageButton2" runat="server" ImageUrl="images/edit.png"/>
                </ItemTemplate>
            </asp:TemplateField> 

        </Columns>
        <EditRowStyle BackColor="#2461BF" />
        <FooterStyle BackColor="#507CD1" Font-Bold="True" ForeColor="White" />
        <HeaderStyle BackColor="#507CD1" Font-Bold="True" ForeColor="White" />
        <PagerStyle BackColor="#2461BF" ForeColor="White" HorizontalAlign="Center" />
        <RowStyle BackColor="#EFF3FB" />
        <SelectedRowStyle BackColor="#D1DDF1" Font-Bold="True" ForeColor="#333333" />
        <SortedAscendingCellStyle BackColor="#F5F7FB" />
        <SortedAscendingHeaderStyle BackColor="#6D95E1" />
        <SortedDescendingCellStyle BackColor="#E9EBEF" />
        <SortedDescendingHeaderStyle BackColor="#4870BE" />
       </asp:GridView>

Does someony know how to allow sorting by columns?

Answer 1

The GridView does not sort itself. You need to add some code for a GridView sorting event and wire it up.

First, you add the name of the OnSorting event to the GridView on the .aspx page:

<asp:GridView ID="gridView" OnSorting="gridView_Sorting" runat="server" />

Then, you add that event in the code-behind. This example also handles changing the sort direction -- once the user has sorted, they may want to reverse the sort direction, and you have to keep track of that.

   private string ConvertSortDirectionToSql(SortDirection sortDirection)
    {
       string newSortDirection = String.Empty;

   switch (sortDirection)
   {
      case SortDirection.Ascending:
             newSortDirection = "ASC";
             break;

      case SortDirection.Descending:
         newSortDirection = "DESC";
         break;
   }

   return newSortDirection;
}

protected void gridView_Sorting(object sender, GridViewSortEventArgs e)
{
   DataTable dataTable = gridView.DataSource as DataTable;

   if (dataTable != null)
   {
      DataView dataView = new DataView(dataTable);
      dataView.Sort = e.SortExpression + " " + ConvertSortDirectionToSql(e.SortDirection);

      gridView.DataSource = dataView;
      gridView.DataBind();
   }
}