I found a free survey application called NSurvey. It’s a free ASP.NET survey application written in .NET. Here’s the official list of features:

• User friendly web based administration interface.
• Unlimited paging support
• Page navigation (previous / next)
• Survey progress can be saved and resumed later
• Value piping from query, session, cookie or server variables
• Client (javascript) & server side field validity checks (Numeric, dates etc...)
• Receive an email report after each entry completion
• Single or matrix question layouts
• Flexible form engine allowing you to create almost any form
• Extensible security addins architecture (click here for a schema)
• Cookie and IP security addins to prevent double submissions
• ASP.net context security addin (Forms , Windows authentication etc...)
• Restrict survey entry on email code using the email code security addin
• XML answer "feeder" (eg: countries, us states ...)
• Specify a maximum / minimum answers required for each question
• Email invitations
• Full multi-language support
• Conditional question branching logic
• Reports filtering through custom rules
• Editable detailed individual vote reports
• Opening / closing date
• Scored surveys to create tests, quizzes
• Protect your survey with a password security addin or a "thank you" message
• Custom redirection URL at the end of the survey
• Customizable design with visual studio / webmatrix designer support
• Open API
• Last but not least ... It's free!

It’s definitely better than writing your own.