If you set AllowPaging="true" or AllowSorting="true" on a GridView control without using a DataSourceControl DataSource (i.e. SqlDataSource, ObjectDataSource), you will run into the following errors:

When changing the page on the GridView control:

The GridView 'GridViewID' fired event PageIndexChanging which wasn't handled.

When clicking a column name to sort the column on the GridView control:

The GridView 'GridViewID' fired event Sorting which wasn't handled.

As a result of not setting the DataSourceID property of the GridView to a DataSourceControl DataSource, you have to add event handlers for sorting and paging.

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

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_PageIndexChanging(object sender, GridViewPageEventArgs e)
{
   gridView.PageIndex = e.NewPageIndex;
   gridView.DataBind();
}

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();
   }
}