SqlDataSource Events Selecting And Selected Not Work

When I handle a event for selecting to change the value of a parameter it does not use the new value and the selected event is never called. What am I doing wrong?

 

protected void OptionListSource_Selecting(object sender, SqlDataSourceSelectingEventArgs e)

{

string productID = Request.QueryString["p"].ToString();

SqlDataSourceView Source = (SqlDataSourceView)sender;

Source.SelectParameters["ProductID"].DefaultValue=productID;



}

protected void OptionListSource_Selected(object sender, SqlDataSourceStatusEventArgs e)

{

SqlDataSourceView Source = (SqlDataSourceView)sender;

}