ASP.NET SelectParameter / Control Parameter usage

Question

newbie to asp.net here.

I am trying to setup a selectparameters and controlparameters based off textbox web controls for date ranges to retrieve data on a asp.net page.

SelectCommand="SELECT SUM(Turnover) AS TotalTurnover, (SUM(Turnover) / (SELECT COUNT(*) FROM (SELECT DISTINCT [Trade Date] FROM TradeSummary WHERE ([Trade Date] BETWEEN @T1 AND @T2)))) AS AverageTO FROM TradeSummary WHERE ([Trade Date] BETWEEN @T1 AND @T2)">
                        <SelectParameters>
                            <asp:ControlParameter ControlID="TradeDate1" DefaultValue="8-10-2012" Name="T1" Type="DateTime" PropertyName="Text" />
                            <asp:ControlParameter ControlID="TradeDate2" DefaultValue="8-11-2012" Name="T2" Type="DateTime" PropertyName="Text" />
                    </SelectParameters>

TradeDate1 and TradeDate2 refer to 2 textbox controls that I setup for date picking.

I am wondering how I can examine the values of @T1 and @T2 so that I can ensure the query being passed to the DB is valid because it seems like if I were to eval("TotalTurnover") then I get a dbnull error.

Any help would be appreciated. Thanks!

Answer 1

you can also pass the control paraamters from your code behind after checking the values. Add the below code in your Page_Load or any other control event ( e.g button )

// check your textbox values
if( TradeDate1.Text != null )
{
   SqlDataSource1.SelectParameters.Add("@T1",TradeDate1.Text);
}