These are called breaking changes for a reason – in upgrading to ASP.NET 4, you run the chance of running into any of these things that can break your website.  I recently updated my account with DiscountASP and moved this domain to a Windows Server 2008/.NET 4 environment.  The next step was to get my TDPE stages in place, which required addressing web.config inheritance issues.  Today, I wanted to post about TDPE 2 launching… only to be greeted with the request validation errors. Um… this worked just fine, why am I seeing this now?  Oh yeah… I moved servers….

So, if you’re moving your BlogEngine blog to a .NET 4 environment fron a .NET 2 environment and have some validateRequest=”False” files, make sure that the following setting appears in your web.config:

<httpRuntime requestValidationMode=”2.0″ />

For this and other breaking changes, see the ASP.NET 4 Breaking Changes whitepaper.