Hi Yma,
Ths is not related to the Store module but to how ASP.NET works! You need a really good book on this subject, I can't give you a title because my books are in French. :-) You have to understand that I can't support ASP.NET for the world. I always explain that the Store module is not a simple one, because it use several advanced concept like the dynamic generation of controls to build the Catalog. This require a stong knowledge about ASP.NET.
If your code is in the button click event, you can't use the sender object to do what you try. The sender object is a reference to the object source of the event, in this case the button not the dropdownlist nor the textbox. As explain in my previous post, your controls are generated "on the fly". You have to give them an id to be able to retreive them at runtime (when the user click on the button).
Start ASP.NET crash course:
In the token code (ProductList.cs - processToken) you need something like that:
TextBox txtMYSEARCH = new TextBox();
txtMYSEARCH.ID = "txtMYSEARCH";
DropDownList ddMYSEARCH = new DropDownList();
ddMYSEARCH.ID = "ddMYSEARCH";
And in the button click event code, you need this to retreive a reference to your controls:
TextBox txtMYSEARCH = (TextBox)this.FindControl("txtMYSEARCH");
DropDownList ddMYSEARCH = (DropDownList)this.FindControl("ddMYSEARCH");
End of ASP.NET crash course.
Gilles