SharePoint 2007 Forms Authentication Error "Value cannot be null."

Every so often, users logging into a SharePoint 2007 portal via forms authentication with a custom membership provider get the following error message. Once the message starts to be received, it will continue to function in that manner.

Value cannot be null.
Parameter name: value at System.String.EndsWith(String value, StringComparison comparisonType)
at Microsoft.SharePoint.ApplicationRuntime.SPRequestModule.PostAuthenticateRequestHandler(Object oSender, EventArgs ea)
at System.Web.HttpApplication.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

The error was not resulting from any of my code which made this incredibly hard to figure out. If you restart the IIS and the OWSTimer, the issue goes away (for a while), but doesn't fix this issue.

This morning I was searching around with a very odd set keywords and ran across this article, Fixing the Elusive “Value Cannot Be Null” FBA Authentication Error. The page doesn't contain the error text or a specific solution, but it does contain a screen shot of exactly what I was experiencing.

I have included the text and solution in this blog to make it crawl-able.

The solution:
The issue appears to be the fact that the web.config, C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\12\TEMPLATE\LAYOUTS\web.config, in the layouts directory of the hive has batch compilation set to false.

<compilation batch="false" batchTimeout="600" maxBatchSize="10000" maxBatchGeneratedFileSize="10000" />

The line should read:

<compilation batch="true" batchTimeout="600" maxBatchSize="10000" maxBatchGeneratedFileSize="10000" />

After making this change, the performance of the site in general improved significantly on the Windows and Forms authentication sides. It looks like an all-around win.


Batch Compilation Information:
From Microsoft's KB article, How to use the "batch" attribute of the Web.config file compilation element in SharePoint Server 2007 and in Windows SharePoint Services 3.0:

The batch attribute is used by the ASP.NET compilation element. This attribute controls all compilation for applications to which the Web.config file applies.

When the attribute is set to "true," the delay that you experience when you access files for the first time can be decreased. This is because, when the batch attribute is set to "true," all uncompiled files will be compiled in batch mode by ASP.NET.

However, for larger applications, there may be a significant delay when files are compiled for the first time because there are more file batches to compile. After the initial compilation, delays are decreased when you access the compiled files.

Microsoft has an excellent web performance best practices site, Developing High-Performance ASP.NET Applications. The pertinent part for our issue:

Consider precompiling
A Web application is batch-compiled on the first request for a resource such as an ASP.NET Web page. If no page in the application has been compiled, batch compilation compiles all pages in a directory in chunks to improve disk and memory usage. You can use the ASP.NET Compilation Tool (Aspnet_compiler.exe) to precompile a Web application. For in-place compilation, the compilation tool calls the ASP.NET runtime to compile the site in the same manner as when a user requests a page from the Web site. You can precompile a Web application so that the UI markup is preserved, or precompile the pages so that source code cannot be changed. For more information, see How to: Precompile ASP.NET Web Sites.

This article explains in depth how debug and batch compilation works. It is worth the read. ASP.NET Resources - Beware Of Deploying Debug Code In Production