Is there a simple way to test if the contents of a TextBox have been changed?

I have a page in the ASP.NET 3.5 app I am developing that has several text boxes for capturing user input. Each text box is initially populated with data (if any) previously stored in my SQL Server database. There is a button on the page to initiate the processing of any changes.

When processing the button click event, I want to find out which text boxes have been changed. I could create my own code, linked to the TextChanged event of each text box, but I was wondering if there was an even simpler way - something analogous to the 'dirty' property in Access. For example, can ViewState be used in some way to achieve this? I'm still an ASP.NET newbie, so any guidance would be appreciated.

David  
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