【一个巨简单的有关问题】个很简单的有关问题：怎么从后台传参给SelectParameters？

【求助一个巨简单的问题】个很简单的问题：如何从后台传参给SelectParameters？？？
如下代码：

 <asp:SqlDataSource ID="SqlDataSource4" runat="server" 
                                                                                        ConnectionString="<%$ ConnectionStrings:LH700ConnectionString %>" 
                                                                                        SelectCommand="SELECT [DocEntry], [LineNum], [ItemCode], [Dscription],[Quantity], [U_U001], [U_DW], [U_ZMJ], [U_U012],[Price], 
                                                                                                               [PriceBefDi],[U_ZK], [LineTotal],[INMPrice],[ShipDate],[U_U018], [U_NDFL], [U_JDFL], [U_YDFL], [U_ZXFL], [U_GGFL],
                                                                                                               [U_ZLFL] FROM [PRE_RDR1] WHERE [DocEntry] = @DocEntry" >
                                                                                      <SelectParameters>
                                                                                        <asp:ControlParameter ControlID="NewGridView" Name="DocEntry" PropertyName="SelectedValue" /> 
 
                                                                                      </SelectParameters>

                                                                                    </asp:SqlDataSource>

private void defineDataSet()
        {
            string connStr = ConfigurationManager.ConnectionStrings["LHT400ConnectionString"].ToString();
            SqlConnection conn = new SqlConnection(connStr);
            dsOrderLine = new DataSet();
            dsOrder = new DataSet();
            int docentry = Convert.ToInt16(Session["DocEntry"]);


            conn.Open();

 this.SqlDataSource1.SelectParameters["pName"] = value;
            this.SqlDataSource1.DataBind();