asp.net SelectParameters: use variable from code

Today I was building a GridView and wanted to set the SelectParameters of the SqlDataSource to use a value that was being sent in the query string.  But then I realized that the value I needed was not being sent in the query string and I didn't want to change the calling page to send the parameter that I needed.  What I wanted to do was to run a query in Page_Load to get the value I needed, store it in a variable, and then assign that variable to some SelectParameter.  But I'd never set the value of a SelectParameter to a value stored in a variable.

When I did a search, I found this solution that uses a generic .  That looked promising, but I couldn't get it to work.  I figured I could copy my variable into a Session variable, and then use a , but that seemed like overkill to create a Session variable just for that page.

The solution ended up being pretty simple.  What I did was:

•  create a TextBox control on the page
• set the TextBox Text property to the value of my variable obtained from the query in Page_Load
• use a ControlParameter for the SelectParameter of the data source and specify that TextBox control as the control from which to get the value

In my case, it turned out that I could keep the control visible on the page because it was useful information, but if that isn't option for you then you could just set the control's visibility to false.