Search Problem-gridview, sqldatasource

I want to implement search. The user can input a From Date, To Date, Department and Name.  When the search button is clicked, I want the search results to be displayed in a gridview. I already have a stored procedure that is working. I configured the sqldatasource using the wizard. When I Test Query it, it works fine. However, when I view it in browser, it always displays "No entry found".  Here's my code:
<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" DataSourceID="SqlDataSource2"> <Columns> <asp:BoundField DataField="RISID" HeaderText="RISID" InsertVisible="False" ReadOnly="True" SortExpression="RISID" /> <asp:BoundField DataField="DateReq" ...