Classificando dados com controles de fonte de dados

<asp:LinqDataSource 
    ContextTypeName="ExampleDataContext" 
    TableName="Products" 
    AutoPage="true"
    AutoSort="true"
    ID="LinqDataSource1" 
    runat="server">
</asp:LinqDataSource>
<asp:GridView 
    AllowPaging="true"
    AllowSorting="true"
    DataSourceID="LinqDataSource1"
    ID="GridView1" 
    runat="server">
</asp:GridView>

<asp:GridView ID="EmployeesGridView" 
  DataSourceID="EmployeesSqlDataSource" 
  DataKeyNames="EmployeeID" 
  AllowSorting="True"
  RunAt="Server" />

<asp:SqlDataSource ID="EmployeesSqlDataSource"  
  SelectCommand="SELECT EmployeeID, LastName, FirstName FROM Employees" 
  Connectionstring="<%$ ConnectionStrings:NorthwindConnectionString %>" 
  RunAt="server" />

<asp:ObjectDataSource 
  ID="EmployeesObjectDataSource" 
  runat="server" 
  TypeName="Samples.AspNet.Controls.NorthwindEmployee" 
  SortParameterName="SortColumns"
  EnablePaging="true"
  StartRowIndexParameterName="StartRecord"
  MaximumRowsParameterName="MaxRecords" 
  SelectMethod="GetAllEmployees" >
</asp:ObjectDataSource>

public static void Initialize()
{
  // Initialize data source. Use "Northwind" connection string from configuration.

  if (ConfigurationManager.ConnectionStrings["Northwind"] == null ||
      ConfigurationManager.ConnectionStrings["Northwind"].ConnectionString.Trim() == "")
  {
    throw new Exception("A connection string named 'Northwind' with a valid connection string " + 
                        "must exist in the <connectionStrings> configuration section for the application.");
  }

  _connectionString = 
    ConfigurationManager.ConnectionStrings["Northwind"].ConnectionString;

  _initialized = true;
}


// Select all employees.

[DataObjectMethod(DataObjectMethodType.Select, true)]
public static DataTable GetAllEmployees(string sortColumns, int startRecord, int maxRecords)
{
  VerifySortColumns(sortColumns);

  if (!_initialized) { Initialize(); }

  string sqlCommand = "SELECT EmployeeID, LastName, FirstName, Address, City, Region, PostalCode FROM Employees ";

  if (sortColumns.Trim() == "")
    sqlCommand += "ORDER BY EmployeeID";
  else
    sqlCommand += "ORDER BY " + sortColumns;

  SqlConnection conn = new SqlConnection(_connectionString);
  SqlDataAdapter da  = new SqlDataAdapter(sqlCommand, conn); 

  DataSet ds =  new DataSet(); 

  try
  {
    conn.Open();
    da.Fill(ds, startRecord, maxRecords, "Employees");
  }
  catch (SqlException e)
  {
    // Handle exception.
  }
  finally
  {
    conn.Close();
  }

  if (ds.Tables["Employees"] != null)
    return ds.Tables["Employees"];

  return null;
}


//////////
// Verify that only valid columns are specified in the sort expression to avoid a SQL Injection attack.

private static void VerifySortColumns(string sortColumns)
{
  if (sortColumns.ToLowerInvariant().EndsWith(" desc"))
    sortColumns = sortColumns.Substring(0, sortColumns.Length - 5);

  string[] columnNames = sortColumns.Split(',');

  foreach (string columnName in columnNames)
  {
    switch (columnName.Trim().ToLowerInvariant())
    {
      case "employeeid":
        break;
      case "lastname":
        break;
      case "firstname":
        break;
      case "":
        break;
      default:
        throw new ArgumentException("SortColumns contains an invalid column name.");
        break;
    }
  }
}