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TFS Error: MSB4018 The "BuildShadowTask" task failed unexpectedly

TL;DR; Explains the MSB4018 “BuildShadowTask” error in TFS when using Accessors in unit test projects, its cause, and how removing .accessor files resolves build issues.

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There seams to be a problem in MSBuild when you add an “Accessor” as part of a Unit Test project.

 1C:Program FilesMSBuildMicrosoftVisualStudiov9.0TeamTestMicrosoft.TeamTest.targets(14,5): error MSB4018: The "BuildShadowTask" task failed unexpectedly.
 2System.IO.FileLoadException: API restriction: The assembly 'file:///C:WINDOWSMicrosoft.NETFrameworkv2.0.50727System.Web.dll' has already loaded from a different location. It cannot be loaded from a new location within the same appdomain.
 3   at System.Reflection.Assembly._nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, Assembly locationHint, StackCrawlMark& stackMark, Boolean throwOnFileNotFound, Boolean forIntrospection)
 4   at System.Reflection.Assembly.nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, Assembly locationHint, StackCrawlMark& stackMark, Boolean throwOnFileNotFound, Boolean forIntrospection)
 5   at System.Reflection.Assembly.InternalLoad(AssemblyName assemblyRef, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection)
 6   at System.Reflection.Assembly.InternalLoadFrom(String assemblyFile, Evidence securityEvidence, Byte[] hashValue, AssemblyHashAlgorithm hashAlgorithm, Boolean forIntrospection, StackCrawlMark& stackMark)
 7   at System.Reflection.Assembly.ReflectionOnlyLoadFrom(String assemblyFile)
 8   at Microsoft.VisualStudio.TestTools.UnitTesting.Publicize.WebBinder.LoadData()
 9   at Microsoft.VisualStudio.TestTools.UnitTesting.Publicize.WebBinder.Init()
10   at Microsoft.VisualStudio.TestTools.UnitTesting.Publicize.Shadower..ctor()
11   at Microsoft.VisualStudio.TestTools.BuildShadowReferences.BuildShadowTask.Execute()
12   at Microsoft.Build.BuildEngine.TaskEngine.ExecuteInstantiatedTask(EngineProxy engineProxy, ItemBucket bucket, TaskExecutionMode howToExecuteTask, ITask task, Boolean& taskResult)

An Accessor allows your test project to access code that would normally be “Private” or “Friend” from outside the Assembly that it resides in.

TFS Error: MSB4018 The "BuildShadowTask" task failed unexpectedly

It creates a little file with the “.accessor” extension that is the same name as your DLL, and contains the name of the DLL.

TFS Error: MSB4018 The "BuildShadowTask" task failed unexpectedly

If you remove this file then your remote MSBuild server will then build you solution successfully again including running your Unit Tests.

Reference:

Re: BuildShadowTask Failed unexpectedly - Accessor Problem (Upconvert VS 2005 to 2008) – URGENT

BuildShadowTask Failed unexpectedly - Accessor Problem (Upconvert VS 2005 to 2008) – URGENT

Technorati Tags: ALM   TFBS   TFS 2008   VS 2005

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