Just wanted to give a heads up on two issues that we are aware of that were introduced with .NET 3.5 SP1.
Reason: 3.5 SP1 added a settable Action property to the HtmlForm type. This new feature makes it much easier for developers to explicitly set the form’s action attribute for scenarios where a developer wants to use a different Url than the normal postback-generated Url. However this change also means that if the action attribute has been set in an .aspx page’s declarative markup, ASP.NET will use the setting from the markup when rendering a <form /> element.
Workaround: Previous versions of ASP.NET always ignored the action attribute if it was present in the declarative markup for a <form /> element. Developers should remove the action attribute from their declarative markup to return to the original behavior where ASP.NET renders the postback Url.
Example: Before (the action attribute was ignored by ASP.NET as dead code):
<form name="form1" method="post" runat="server" action="test.aspx"></form>
3.5 SP1 (remove the action attribute to have ASP.NET render the postback Url):
<form name="form1" method="post" runat="server" ></form>
The behavior you are seeing is the original behavior of ASP.NET 2.0. When the .NET Framework 3.5 and Visual Studio 2008 were introduced, a bug was introduced that affected certain pageBaseType scenarios that unfortunately were not intended. It seems as if you might have run into one of these scenarios. In the .NET Framework 3.5 SP1, the bug was fixed and these scenarios no longer occur; pageBaseType again works the same as in ASP.NET 2.0, as requested by customers. Unfortunately, this means that customers who have relied on the unintended behavior that was introduced in the .NET Framework 3.5 will now encounter problems when they run their applications.
Here are some details about the issue; we will post a more detailed description soon. The mismatch is caused by the class in the code file not being assignable to the pageBaseType that is defined in the web.config file. The sequence that occurs is this:
Both of these issues are also mentioned here.