XHTML 1.1 and DataBinding (Chapter Excerpt #2)

When doing serious data binding in ASP.NET you may want to reconsider using XHTML 1.1 or XHTML 1.0 Strict at all. The rule is simple: use the document type that can be deterministicly proven to be proper in your situation. Put another way, unless you have deterministicly proven that there will never be any invalid markup in the data, you should always use XHTML 1.0 Transitional.

If the binding data has some odd markup, then you will end up sending invalid XHTML 1.0 sent to IE breaking validation or sending invalid XHTML 1.1 markup to browsers such as Firefox, halting the rendering.

But what does it mean to be deterministicly proper? To put it simply it means to absolutely garuntee that the data will always be proper, that is, to be able to always predict the properness of data. This does not mean "well, it worked for 100,000 tests, so it's good enough", but rather it means that it absolutely will always work 100% of the time. You can get this level of determinism by looking at the symantics of what is going to be bound. For example, if you are binding a table with numbers, which will always be numbers, then you should have a level of determinism here. However, if you are binding a table with unvalidated under input, then you do not have determinism as you have no idea what a user will input. The user could input <b><i></b></i>, which will break the page. You have no idea. Having a proven, not demonstrated, view of data is what this is all about.

Here are a few guidelines that should help you with determining what is and not deterministic.

These things are never deterministic...

• Unvalidated user input
• Unvalidated external data
• HTML
• Anything else with angle brackets (<, >), except wellformed XML

Given symantical care, these things should be deterministic...

• Wellformed XML
• Alphanumeric strings
• Base64 encoded data
• Alphanumeric strings

To reiterate: only use the document type that is deterministicly proven to always be proper.