sql - ASP.NET SqlDataSource, like on SelectCommand -

i'm working on asp.net. have sqldatasource query hardcoded on selectcommand:

<asp:sqldatasource id="datasource1" runat="server" cancelselectonnullparameter="false"     connectionstring="<%$ connectionstrings:s.properties.settings.connectionstring %>"      selectcommand="select * [table]     ([col1] case @col1_param when null col1 else @col1_param end)     ,  ([col2] case @col2_param when null col2 else @col2_param end)"     selectcommandtype="text">     <selectparameters>         <asp:controlparameter controlid="textbox1" name="col1_param" propertyname="text"             type="string" />         <asp:controlparameter controlid="textbox2" name="col2_param" propertyname="text"             type="string" />     </selectparameters> 

what want if enter data on 1 textbox only, data display according textbox value on clause. , if no values placed neither of textboxes, the query executes if there no where.

right code,what happens if put on 1 textbox no data displayed. same if textboxes empty.

i don't want use sql stored procedure.

how can solve this?

thanks...

assuming passes null when there no text entered, otherwise need check empty string

selectcommand="select * [table]     ([col1] '%@col1_param%' or @col1_param null)     ,  ([col2] '%@col2_param%' or @col2_param null)"