I upgraded an OCX library from VS2010/Win7 to VS2019/Win10. The project builds, however when I try and use RegSvr32.exe from an elevated command prompt, I receive error 0x0040200. I did a bit of debugging and the offending call is the call to AfxOleRegisterTypeLib.
Yes, I saw this SO article, which states that "absence of a tlb file near the dll". Other searches state to run from an administrative command prompt.
I do NOT have a TLB near the OCX control. If I try and create one using tlbexp.exe, I get the following error:
TlbExp : error TX0000 : Could not load file or assembly 'file:///C:\pathto.ocx' or one of its dependencies. The module was expected to contain an assembly manifest.
TlbExp command line (used Run as Administrator for all cmd.exe):
"C:\Program Files (x86)\Microsoft SDKs\Windows\v10.0A\bin\NETFX 4.7.2 Tools\x64\tlbexp.exe" /VERBOSE "<path to OCX file>" /out:"<path to .tlb output file>"
I downloaded Resource Tuner and that shows the manifest nicely. The manifest does not have any TLB information.
I am thinking that maybe the OCX manifest needs something more that helps TlbExp get at the information that it wants, just a thought.
<?xml version="1.0" encoding="utf-8"?>
<assembly manifestVersion="1.0" xmlns="urn:schemas-microsoft-com:asm.v1">
<assemblyIdentity version="1.0.0.0" name="DriveOps.ocx"/>
<trustInfo xmlns="urn:schemas-microsoft-com:asm.v2">
<security>
<requestedPrivileges xmlns="urn:schemas-microsoft-com:asm.v3">
<requestedExecutionLevel level="requireAdministrator" uiAccess="false" />
</requestedPrivileges>
</security>
</trustInfo>
<compatibility xmlns="urn:schemas-microsoft-com:compatibility.v1">
<application>
<!-- Windows 7 -->
<supportedOS Id="{35138b9a-5d96-4fbd-8e2d-a2440225f93a}" />
<!-- Windows 8 -->
<supportedOS Id="{4a2f28e3-53b9-4441-ba9c-d69d4a4a6e38}" />
<!-- Windows 8.1 -->
<supportedOS Id="{1f676c76-80e1-4239-95bb-83d0f6d0da78}" />
<!-- Windows 10 -->
<supportedOS Id="{8e0f7a12-bfb3-4fe8-b9a5-48fd50a15a9a}" />
</application>
</compatibility>
<application xmlns="urn:schemas-microsoft-com:asm.v3">
<windowsSettings>
<dpiAware xmlns="http://schemas.microsoft.com/SMI/2005/WindowsSettings">true</dpiAware>
</windowsSettings>
</application>
</assembly>
I did use Depends64 (aka Dependency Walker 64-bit) and there are no missing components DLLs. It finds all of them nicely, as does RegSvr32.exe.
Placing the OCX file in C:\Windows\System32 does not help.
To anyone looking at the DLLs, these same DLLs work fine on the Win7 box. Here is some more information on the non-Windows DLLs
PlxApi720_x64.dll: PLX v7.2 API (The Broadcom PLX chip is a PCIe switch (think USB/network switch, just w/PCIe lanes)
LSIDirectAccess.dll: The LSI API is a self-contained DLL that allows the software to talk to the LSI HBA RAID adapter
Ipp*.dll: The Ipp prefix are the DLLs used by the Intel Code Composer Studio redistribution (x64) files, here version 2011, an older one that needs to be updated to the latest and greatest, not to mention now free API. These are all in the System32 folder.
Here is the code:
// DllRegisterServer - Adds entries to the system registry
STDAPI DllRegisterServer(void)
{
AFX_MANAGE_STATE(_afxModuleAddrThis);
if (!AfxOleRegisterTypeLib(AfxGetInstanceHandle(), _tlid))
return ResultFromScode(SELFREG_E_TYPELIB); // <- failure line, through debugging
if (!COleObjectFactoryEx::UpdateRegistryAll(TRUE))
return ResultFromScode(SELFREG_E_CLASS);
return NOERROR;
}
The Intel Code Composer Studio 2011 files are in the C:\Windows\System32 directory, just like on the Win7 box.
For what it is worth, TlbExp fails on the Win7 box too, just it registers, which is probably why the UI can add the control. As I recall, I once replaced the OCX on the Win7 project and VS2010 automatically created the TLB and prefixed Ax in front, but that was a couple of years ago, so my memory may not be the most accurate. Attempting to add the OCX to the UI (.Net WinForms) fails miserably and just says could not be added.
The OCX does use the latest platform tool set (Visual Studio 2019 (v142)).
A comment for developer newbies, regasm.exe is for .Net Assemblies. RegSvr32.exe is for ActiveX Controls (OCX/DLL), which is what I have. RegSvr32 is for dynamically loaded modules, hence the DllRegister entry point.
Thoughts?
Notes From Further Testing
(Saturday 9/21/2019) When I upgraded, I created an empty C++ DLL project and then added all the files, changing the target extension to OCX going through the old project settings and when reasonable aligning them to the new project file wanting to keep things the same. I wanted to do a test and see what happens with a brand new OCX project. I saw that there was such a thing as "MFC ActiveX Control" for a project type in VS2019. I created that and saw that I got different base files, but more importantly RegSvr32.exe works. That means that either the mistake was the initial project file, so I need to import to a clean project or import piece by piece, if that is possible, and see where things break.
(Saturday 9/21/2019) The new test project did not come with a manifest file and TlbExp.exe failed with the same error message like my real project. I went to add new item and saw "Package Manifest". That manifest file, though still produces the same TlbExp.exe error, looks quite different from the application manifest file from above. I created yet another new MFC ActiveX Control project and added in the manifest from above just changing names and saw that the project refused to build throwing 1) Error c1010001 Values of attribute "level" not equal in different manifest snippets. and 2) LNK1327 failure during running mt.exe. That tells me that the original Win7 project and my Win10 project files probably have some error in it, otherwise VS should have thrown these errors to me. That does not answer why even on the test project TlbExp.exe fails. Maybe some attributes in the manifest are required. I just left the defaults.
Package Manifest
(It is the first time that I ever saw one of these. I always saw the app.manifest kind.)
<?xml version="1.0" encoding="utf-8"?>
<!-- TODO: Make sure to set the Package attributes -->
<Package xmlns="urn:Microsoft.WindowsPhone/PackageSchema.v8.00"
Owner=""
OwnerType="OEM"
Platform=""
Component=""
SubComponent="Package"
ReleaseType="Test" >
<Components>
<Driver InfSource="$(_RELEASEDIR)$(TARGETNAME).inf">
<Reference Source="$(_RELEASEDIR)$(TARGETNAME)$(TARGETEXT)" />
<Files>
<!-- For kernel mode drivers, $(DRIVER_DEST) evaluates to "drivers" by default -->
<!-- For user mode drivers, $(DRIVER_DEST) evaluates to "drivers\umdf" by default -->
<File Source="$(_RELEASEDIR)$(TARGETNAME)$(TARGETEXT)" DestinationDir="$(runtime.system32)\$(DRIVER_DEST)" />
</Files>
</Driver>
</Components>
</Package>
This article has an interesting approach, namely create a C++ DLL and then call LoadLibrary(dll) and after that GetProcAddress(module, "DllRegisterServer") to see which one fails. Well, in my case the both functions succeed. That means that the author missed one other failure branch and these two API calls are not the only thing that RegSvr32.exe does.
Though I am still not at the end of the road, as I have aximp.exe / tlbimp.exe issues on the OCX, I found the problem that prevented me from registering the ActiveX control, which was the question here.
The answer is the GUID in the main CPP file:
(I am giving my research, as I could not find anyone explaining how RegSvr32.exe works and what it does. I wanted to share in hopes that it helps others.)
const GUID CDECL _tlid = { 0xFE5C7D88,0xD53C,0x4977,{0xBA,0x56,0x4B,0xF3,0x02,0x0A,0x5D,0x8A} };
which gets used in the main registration function STDAPI DllRegisterServer(void) must match the GUID present in the IDL:
[uuid(FE5C7D88-D53C-4977-BA56-4BF3020A5D8A), version(1.0),
helpfile("DriveOps.hlp"),
helpstring("DriveOps ActiveX Control module"),
control]
library DriveOpsLib
{
...
}
I had 2 different values, hence the failure.
Here is the methodology and research that I used to find the problem, but first I will state the registration function, as that is key again.
STDAPI DllRegisterServer(void)
{
AFX_MANAGE_STATE(_afxModuleAddrThis);
HINSTANCE hiTypeLib = AfxGetInstanceHandle();
if (!AfxOleRegisterTypeLib(hiTypeLib, _tlid))
return ResultFromScode(SELFREG_E_TYPELIB);
if (!COleObjectFactoryEx::UpdateRegistryAll(TRUE))
return ResultFromScode(SELFREG_E_CLASS);
return NOERROR;
}
The failure was at this line, as I believe was mentioned in the question.
if (!AfxOleRegisterTypeLib(hiTypeLib, _tlid))
I had already found the source code for RegSvr32.exe on the internet. It was part of Microsoft GitHub sources located in VCSamples-master.
Direct Link to RegSvr32.exe: here
Direct Link to download zip: here
The code was a sort of dead end, as it told me what should have been obvious, namely that utility called the DllRegisterServer entry point of a DLL to do all the work. I should have known that, but, well, I had to see it to make sense.
Using procmon.exe, did not shed any light and the various calls to the registry was like reading a foreign language, not helpful.
Here I drew a blank until it occurred to me to get the source code for AfxOleRegisterTypeLib, as that what was failing. I wanted to see what the heck that thing did and what was at line 113 of source file ctlreg.cpp.
I was still thinking on the comment of procmon and a registry issue, but I figured that the code will tell me which one. It took me a bit of research, but I found the code. I love Microsoft sharing code. Their error messages are not helpful, but being able to actually see what they were trying to do so totally helps.
Here is the code:
BOOL AFXAPI AfxOleRegisterTypeLib(HINSTANCE hInstance, REFGUID tlid,
LPCTSTR pszFileName, LPCTSTR pszHelpDir)
{
USES_CONVERSION;
BOOL bSuccess = FALSE;
CString strPathName;
TCHAR *szPathName = strPathName.GetBuffer(_MAX_PATH);
::GetModuleFileName(hInstance, szPathName, _MAX_PATH);
strPathName.ReleaseBuffer();
LPTYPELIB ptlib = NULL;
// If a filename was specified, replace final component of path with it.
if (pszFileName != NULL)
{
int iBackslash = strPathName.ReverseFind('\\');
if (iBackslash != -1)
strPathName = strPathName.Left(iBackslash+1);
strPathName += pszFileName;
}
if (SUCCEEDED(LoadTypeLib(T2COLE(strPathName), &ptlib)))
{
ASSERT_POINTER(ptlib, ITypeLib);
LPTLIBATTR pAttr;
GUID tlidActual = GUID_NULL;
if (SUCCEEDED(ptlib->GetLibAttr(&pAttr)))
{
ASSERT_POINTER(pAttr, TLIBATTR);
tlidActual = pAttr->guid;
ptlib->ReleaseTLibAttr(pAttr);
}
// Check that the guid of the loaded type library matches
// the tlid parameter.
ASSERT(IsEqualGUID(tlid, tlidActual));
if (IsEqualGUID(tlid, tlidActual))
{
// Register the type library.
if (SUCCEEDED(RegisterTypeLib(ptlib, T2OLE((LPTSTR)(LPCTSTR)strPathName), T2OLE((LPTSTR)pszHelpDir))))
bSuccess = TRUE;
}
RELEASE(ptlib);
}
else
{
TRACE1("Warning: Could not load type library from %s\n", (LPCTSTR)strPathName);
}
return bSuccess;
}
I kept receiving an ASSERT, so although line 113 did was on a non-code line, the actual failure was obvious. I knew that I did not fail out on the ASSERT_POINTER, as that error message is different, which meant that I failed at:
ASSERT(IsEqualGUID(tlid, tlidActual));
I looked at the code in detail as well as the entry arguments. I decided to copy and paste this function contents into the real registration code in my OCX to gain further visibility while debugging. I wanted to see the values.
Sure enough, I saw 2 different GUID values, one from the top, my _tlid, and the one returned from the instance handle. I took out my handy-dandy TextPad text editor, though Visual Studio has a Find in Files, but TextPad is so much easier to use. That led to one other instance in the entire solution, namely in DriveOps.idl. That file up until that moment meant nothing to me, but suddenly I saw that the GUID here was the one that RegSvr32.exe pulled from the instance handle.
I unified the IDs, rebuilt, and now RegSvr32.exe no longer complains. Yeah, since I got the code, it had no choice but to register. That it does not modify the registry is a different story and problem from what I can tell, but that is another question. RegSvr32.exe now registers without complaint.
(Yes, I still have tlbimp.exe, aximp.exe, and adding my OCX project to my WinForms project problems, but I got this thing licked and learned something in the process. I guess the difference in line numbers may be some changes Microsoft made in the header, either way, functionality appears the same.)
Great. Issue in all such cases is the IDL has a different GUID as compared to what the DLL / OCX has in code for registration. How it changed, I did not investigate but was able to fix this issue by reading new GUID from project generated *.idl file.
I'm pretty sure I understand the error, I just don't understand why and why now.
Unhandled Exception: System.IO.FileLoadException: Could not load file
or assembly 'Microsoft.WindowsAzure.Storage, Version=9.3.0.0,
Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its
dependencies. The located assembly's manifest definition does not
match the assembly reference. (Exception from HRESULT: 0x80131040)
---> System.IO.FileLoadException: Could not load file or assembly 'Microsoft.WindowsAzure.Storage, Version=7.2.1.0, Culture=neutral,
PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The
located assembly's manifest definition does not match the assembly
reference. (Exception from HRESULT: 0x80131040)
Sure enough the version the web site is:
My question is that this was a running web job which ran successfully back in 2018-09-03 - why is it failing on the versioning of an assembly now?
After this time, we simply turned down the resources of the web site, and waiting for the next time the system would be used.
This year, I cranked up the resources and it's now failing! The Web.config has no reference to this file or the version - so I'm thinking it should just find the dll, but I don't know why it's referring to the 9.3.0.0 version, and why the reference to the 7.2.1.0 version?
I really don't want to take the time to re-deploy and recompile, as that will then require a full regression test - and the client will simply not pay for something that should just be running.
What am I missing?
I have a pretty straight forward WiX project. Nothing fancy. When trying to perform a MajorUpgrade over an existing installation, it is unable to start the service and inevitably rolls back to the previous version and starts the service just fine. I have removed the Start="install" and manually started the application successfully, so I know it's not a dependency issue.
I have searched endlessly and found no answers to my problem.
<MajorUpgrade DowngradeErrorMessage="A newer version of [ProductName] is already installed." Schedule="afterInstallFinalize" />
My service install:
<ServiceInstall
Id="ServiceInstaller"
Type="ownProcess"
Name="LsdnService"
DisplayName="Lsdn Service"
Description="Placeholder for now."
Start="auto"
Account="[SERVICEACCOUNT]"
Password="[SERVICEPASSWORD]"
ErrorControl="normal"/>
<ServiceControl Id="StartService" Start="install" Stop="both" Remove="uninstall" Name="LsdnService" Wait="yes" />
I dumped the MSI log to a file and got this error but it is quite vague.
MSI (s) (18:48) [22:41:27:349]: Note: 1: 2205 2: 3: Error
MSI (s) (18:48) [22:41:27:349]: Note: 1: 2228 2: 3: Error 4: SELECT `Message` FROM `Error` WHERE `Error` = 1920
There are some registry modifications during an installation. The installer attempts to read from the registry and inherit the already existing values.
<Property Id="LSDNADDRESS" Value="127.0.0.1">
<RegistrySearch Id="LsdnAddressProperty" Root="HKLM" Key="$(var.RegistryKey)" Name="LsdnAddress" Type="raw" />
</Property>
<Property Id="LSDNPORT" Value="9920">
<RegistrySearch Id="LsdnPortProperty" Root="HKLM" Key="$(var.RegistryKey)" Name="LsdnPort" Type="raw" />
</Property>
<Property Id="LSDNKEY" Value="6f380b07-0b54-4904-8303-95d1ec45d453">
<RegistrySearch Id="LsdnKeyProperty" Root="HKLM" Key="$(var.RegistryKey)" Name="LsdnKey" Type="raw" />
</Property>
Debugging Results: Following a lot of debugging (by original poster - OP) this turned out to be a known MSI issue described here:
https://wix-users.narkive.com/EMfQPDrM/a-bug-get-reg-sz-when-using-type-integer. Nice search work.
What is in a DWORD? (a REG_SZ apparently): Essentially MSI "converts" a DWORD value found via a RegistrySearch
operation to a formatted string - REG_SZ - during upgrade
installations (could be more involved too). This causes services that
expect a DWORD value to fall over on startup during major
upgrades. A very exotic error.
Workaround: One can try to "solve" this problem by making the service code capable of reading both DWORD and REG_SZ.
This yields a more robust solution than solving the problem in a
custom action since it is a "permanent" fix as long as the code is in
there (and the presence of the code alerts other developers about the
problem). Or maybe use only REG_SZ?
Quick Checks: Check the service password and login - obviously. Anything in the
Event Viewer? Windows Key + Tap R + eventvwr.msc + Enter. How to use the Event Viewer to troubleshoot problems with a Windows Service. Perhaps you can try to do a folder diff on the before and after folders and see if you see something unexpected in
the config files? Naturally there will be lots of binary
differences, but check the text files (also encoding). Check the MSI log file
again and search for "value 3" as described here: Tips For Checking MSI Log
Files. Manually copy the new files in place and attempt to start the service via the services.msc applet.
Service Experts: Windows Services Frequently Asked Questions (FAQ). Content seems to be up to date - at face value at least.
These guys claim to be experts on services. I have no idea who they
are.
Look in the "Errors" section in the link above. Here are some
extracts:
1053: The service did not respond to the start or control request in a timely fashion
Why doesn't my Windows Service start automatically after a reboot?
1069: The service did not start due to a logon failure
Generic Check Lists: If none of the above does anything, maybe try these "torpedoes full spread" check-lists (just ideas to start debugging):
Desktop applicaton not opening after installation in client system
Windows Application Startup Error Exception code: 0xe0434352
General Purpose Debugging: Throwing in some general-purpose debugging approaches.
Custom Action Debugging: WIxsharp debug custom action in console
Dependency Scanning: Which winform project files should be packed up into the installer
Some Further Links:
C# Debug folder when copied to another location does not run the exe
wix service install not enough permission
How exactly does the WiX 'Service Install' work internally?
WiX Toolset PermissionEx Problem - App Does Not Run After Installation
It certainly could be a dependency issue. For example, GAC / WinSXS files don't get installed into the GAC until the commit phase which is after StartServices.
I would leave the Start="Install" in and while it's sitting at the failed to start prompt inspect the state of the machine and debug the service start manually. I bet you'll find something missing.
I am currently trying to upgrade our c++ mfc solution from visual studio 2010 to a visual studio 2013 solution. When i try to build it i get the error MSB4018 The "ResolveComReference" task failed unexpectedly. I enabled fusion logging and this is what it tells me:
=== Pre-bind state information ===
LOG: DisplayName = System
(Partial)
WRN: Partial binding information was supplied for an assembly:
WRN: Assembly Name: System | Domain ID: 1
WRN: A partial bind occurs when only part of the assembly display name is provided.
WRN: This might result in the binder loading an incorrect assembly.
WRN: It is recommended to provide a fully specified textual identity for the assembly,
WRN: that consists of the simple name, version, culture, and public key token.
WRN: See whitepaper http://go.microsoft.com/fwlink/?LinkId=109270 for more information and common solutions to this issue.
LOG: Appbase = file:///C:/Program Files (x86)/MSBuild/12.0/bin/
LOG: Initial PrivatePath = NULL
Calling assembly : Microsoft.Build.Tasks.v12.0, Version=12.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a. ===
LOG: This bind starts in default load context.
LOG: Using application configuration file: C:\Program Files (x86)\MSBuild\12.0\bin\MSBuild.exe.Config
LOG: Using host configuration file:
LOG: Using machine configuration file from C:\Windows\Microsoft.NET\Framework\v4.0.30319\config\machine.config.
LOG: Policy not being applied to reference at this time (private, custom, partial, or location-based assembly bind).
LOG: Attempting download of new URL file:///C:/Program Files (x86)/MSBuild/12.0/bin/System.DLL.
LOG: Attempting download of new URL file:///C:/Program Files (x86)/MSBuild/12.0/bin/System/System.DLL.
LOG: Attempting download of new URL file:///C:/Program Files (x86)/MSBuild/12.0/bin/System.EXE.
LOG: Attempting download of new URL file:///C:/Program Files (x86)/MSBuild/12.0/bin/System/System.EXE.
I understand that msbuild has been moved, but i dont understand why it is trying to find System.dll in the msbuild path, how can i make it look for it in its proper location?
Edit:
I have now also tried upgrading to visual studio 2012 which worked without bigger problems and I did not run into the same problem. However i noticed that when running devenv /upgrade (with vs2013) it seems to completely change everything under vc++ directories (it stayed unchanged when upgrading to vs2012). Could this have something to do with this issue?
Edit2:
Tried to build the project in vs2013 after upgrading it to 2012 (without running devenv /upgrade), this also didnt work so I guess the problem is not related to that...
After enabling diagonostic build output i found that it was 3 broken COM references in the project that where failing to load. Removing these references solved the building issue. These where only showing up as warnings in vs2010 but resulted in MSB4018 in vs 2013 for some reason.
This is your problem:
LOG: Appbase = file:///C:/Program Files (x86)/MSBuild/12.0/bin/
Fix the base folder in your build system if you really need it to point to another filder. However it would probably be better to redo you build system targeting 2013 instead of patching the 2010 version.
I am using Xunit.net with Visual Studio Online hosted build. My tests are being discovered and run fine both locally and on the build server. But on the build server I get this exception (causing the build to reach a "Partially Succeeded" state). This is odd, since all my tests are in fact being discovered and run.
[xUnit.net 00:00:01.3170293] Exception discovering tests from C:\a\bin\xunit.runner.visualstudio.testadapter.dll: System.IO.FileNotFoundException: Could not load file or assembly 'Microsoft.VisualStudio.TestPlatform.ObjectModel, Version=12.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified.
File name: 'Microsoft.VisualStudio.TestPlatform.ObjectModel, Version=12.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' ---> System.IO.FileNotFoundException: Could not load file or assembly 'Microsoft.VisualStudio.TestPlatform.ObjectModel, Version=11.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified.
File name: 'Microsoft.VisualStudio.TestPlatform.ObjectModel, Version=11.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'
WRN: Assembly binding logging is turned OFF.
To enable assembly bind failure logging, set the registry value HKLM\Software\Microsoft\Fusion!EnableLog to 1.
Note: There is some performance penalty associated with assembly bind failure logging.
To turn this feature off, remove the registry value [HKLM\Software\Microsoft\Fusion!EnableLog].
at System.Reflection.RuntimeAssembly.GetExportedTypes(RuntimeAssembly assembly, ObjectHandleOnStack retTypes)
at System.Reflection.RuntimeAssembly.GetExportedTypes()
at Xunit.Sdk.Executor.EnumerateTests..ctor(Executor executor, Object _handler)$$RethrowMarker$$ at ExceptionExtensions.RethrowWithNoStackTraceLoss(Exception ex)
at Xunit.RemoteAppDomainManager.CreateObjectTObject
at Xunit.Xunit1Executor.EnumerateTests(ICallbackEventHandler handler)
at Xunit.Xunit1.Find(Predicate`1 filter, Boolean includeSourceInformation, IMessageSink messageSink)
at Xunit.Xunit1.Find(Boolean includeSourceInformation, IMessageSink messageSink)
at Xunit.XunitFrontController.Find(Boolean includeSourceInformation, IMessageSink messageSink)
at Xunit.Runner.VisualStudio.TestAdapter.VsTestRunner.GetTests(IEnumerable`1 sources, IMessageLogger logger, XunitVisualStudioSettings settings, Stopwatch stopwatch)
See http://go.microsoft.com/fwlink/?LinkId=254169
I have the following nuget packages installed in the test project:
xunit 1.9.2
xunit.runner.visualstudio 0.99.2
Other unit testing frameworks, such as MS Test and NUnit, are working without problems. This makes me think the issue is with Xunit.net rather than with Visual Studio Online.
I have also opened an issue at the xUnit.net GitHub, but it remains unsolved.
https://github.com/xunit/xunit/issues/47
How can I get this working? Does anyone know of a workaround? Could I somehow suppress the error message?
The testrunner tries to discover the unit tests in xunit.runner.visualstudio.testadapter.dll. Why? Because it matches the default test sources spec of *.test*.dll.
When changing the default test source spec to *.tests.dll or something else more specific, it will work.
Source: http://erictummers.wordpress.com/2014/02/11/execute-xunit-tests-on-hosted-build-controller/