You have three lines that reference the Textbox class and, from the error message, it would appear you have imported the windows and web assemblies that reference textbox classes. You have at least two options.

Decide whether you're building a WinForm or a Web solution and remove the other import

or

Explicitly specify whether textbox is a WinForm control or an web server control i.e. System.Forms.We bControls.Textb ox...

When I have a database error I like to log the actual SQL statement that created the error but I've recently modified my code to use parameters to deter SQL injection. I have an example below which works fine except the error messages don't show the actual SQL that caused the error - they just show the parameter placeholders. Does anyone know a way to get to the SQL after the parameter substitution has taken place so I can do accurate error reporting?...