Question

I installed Visual Studio 2010 Beta 2 in an XP Mode VM on Windows 7. Then I created a trivial Silverlight 4 (beta) project and tried to build it. I get the following error:

Error 1 The "ValidateXaml" task failed unexpectedly. System.IO.FileLoadException: Could not load file or assembly file:// sclientdUsersmeDocumentsVisual Studio 2010ProjectsSilverlightApplication2SilverlightApplication2objDebugSilverlightApplication2.dll or one of its dependencies. Operation is not supported. (Exception from HRESULT: 0x80131515)

File name: file:// sclientdUsersmeDocumentsVisual Studio 2010ProjectsSilverlightApplication2SilverlightApplication2objDebugSilverlightApplication2.dll ---> System.NotSupportedException: An attempt was made to load an assembly from a network location which would have caused the assembly to be sandboxed in previous versions of the .NET Framework. This release of the .NET Framework does not enable CAS policy by default, so this load may be dangerous. If this load is not intended to sandbox the assembly, please enable the loadFromRemoteSources switch. See http://go.microsoft.com/fwlink/?LinkId=155569 for more information.

at System.Reflection.RuntimeAssembly._nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, RuntimeAssembly locationHint, StackCrawlMark& stackMark, Boolean throwOnFileNotFound, Boolean forIntrospection, Boolean suppressSecurityChecks) at System.Reflection.RuntimeAssembly.nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, RuntimeAssembly locationHint, StackCrawlMark& stackMark, Boolean throwOnFileNotFound, Boolean forIntrospection, Boolean suppressSecurityChecks) at System.Reflection.RuntimeAssembly.InternalLoadAssemblyName(AssemblyName assemblyRef, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection, Boolean suppressSecurityChecks) at System.Reflection.RuntimeAssembly.InternalLoadFrom(String assemblyFile, Evidence securityEvidence, Byte[] hashValue, AssemblyHashAlgorithm hashAlgorithm, Boolean forIntrospection, Boolean suppressSecurityChecks, StackCrawlMark& stackMark) at System.Reflection.Assembly.LoadFrom(String assemblyFile) at Microsoft.Silverlight.Build.Tasks.ValidateXaml.XamlValidator.Execute(ITask task) at Microsoft.Silverlight.Build.Tasks.ValidateXaml.XamlValidator.Execute(ITask task) at Microsoft.Silverlight.Build.Tasks.ValidateXaml.Execute() at Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute() at Microsoft.Build.BackEnd.TaskBuilder.ExecuteInstantiatedTask(ITaskExecutionHost taskExecutionHost, TaskLoggingContext taskLoggingContext, TaskHost taskHost, ItemBucket bucket, TaskExecutionMode howToExecuteTask, Boolean& taskResult)

I believe this is related to the fact that XP Mode redirects the My Documents folder to the host, turning it into a network share location, and some sort of CAS / security policy is being triggered.

Anyone know how to fix it?

Answer 1

Have you added <loadFromRemoteSources enabled="true"/> in your configuration file?

Answer 2

Enabling loadFromRemoteSources is also explained on http://social.msdn.microsoft.com/Forums/en-US/webdevelopmentprerelease/thread/ea9b9cab-cbfd-496d-8a81-7b3dd06e8c23 along with another option; set the environment variable COMPLUS_EnableLegacyCASPolicy.

Edit: (copy and paste from the above URL as the post got taken down)

David DeWinter - MSFT (Wednesday, May 20, 2009 2:10 AM)

Caveat: I m not on the security team but will attempt to answer this nonetheless...

What s happening here is that the build tasks for Silverlight are attempting to load an assembly that, in previous versions of the CLR, would classify it as a partial trust assembly based on its evidence (e.g. its zone) according to CAS policy.

In CLR 4.0, CAS policy is totally deprecated and is not even enabled by default. Under the circumstances, though, it appears the CLR throws an Exception when what would be a partial trust load in CLR 2.0 is a full trust load in CLR 4.0.

The loadFromRemoteSources switch the Exception message refers to is in the runtime element under configuration and looks like this:

<runtime>
  <loadFromRemoteSources enabled="true|false" />
</runtime>

This will not enable legacy CAS policy but will allow you (or, in this case, the build system) to load remote assemblies with the same permissions as the host AppDomain. In this case it seems as though you could modify the configuration for the build system (which I assume in this case would be Visual Studio: %ProgramFiles%Microsoft Visual Studio 10.0Common7IDEdevenv.exe.config) to enable this switch.

If you don t want to modify that configuration then you can set the environment variable COMPLUS_EnableLegacyCASPolicy to 1, which will enable CAS Policy that was present in CLR 2.0 and also allow Silverlight to load this task.

Hope that helps. David, Blog - http://blogs.rev-net.com/ddewinter/ Twitter - @ddewinter

Answer 3

It should work if you add <loadFromRemoteSources enabled="true"/> to devenv.exe.config. More info at http://msdn.microsoft.com/en-us/library/dd409252%28VS.100%29.aspx

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