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ADO.NET provider with invariant name 'System.Data.SqlClient' could not be loaded

Today blog post will be started with the following error when running DB tests on the CI machine:
threw exception: 
System.InvalidOperationException: The Entity Framework provider type 'System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer' registered in the application config file for the ADO.NET provider with invariant name 'System.Data.SqlClient' could not be loaded. Make sure that the assembly-qualified name is used and that the assembly is available to the running application. See for more information.
    at System.Data.Entity.Infrastructure.DependencyResolution.ProviderServicesFactory.GetInstance(String providerTypeName, String providerInvariantName)

This error happened only on the Continuous Integration machine. On the devs machines, everything has fine. The classic problem – on my machine it’s working. The CI has the following configuration:

  • TeamCity
  • .NET 4.51
  • EF 6.0.2
  • VS2013

It seems that there is an assembly reference that is not copied to the output. If we are looking closes in the error code we notify that ‘EntityFramework.SqlServer’ is missing.
First step: Check the Unit Test project and rest of the projects to see if that assembly is there – YES
Second step: Check the ‘Copy Local’ attribute of the reference to be true – YES
Third step: Check the configuration file of unit test project to specify the SQL provider – YES
    <provider invariantName="System.Data.SqlClient" type="System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer" />
Forth step: Copy the source code directly from CI machine to local machine and use them to run the tests – YES (all tests are green)
Fifth step: Force that specific assembly to be loaded from code. We need to use a class from EntityFramewok.SqlServer
Type providerService = typeof(System.Data.Entity.SqlServer.SqlProviderServices);

And YES, the build is green, all tests are running. It seems that the reference was not copied in the output folder where unit tests are run.

It seems that this is a known problem for EF 6 without an official solution. I hope that in the next release of EF this problem will be solved.


  1. I was facing the same issue with Team City, I had to follow the fifth step.

  2. In my-case, adding solved the issue.
    thanks for the explanation!.

  3. Only the Fifth step worked for me. Excellent post man! Thank you so much!

  4. Thank you very very very much!!! Fifth step worked!

  5. Thank you - the fifth step was the key - with a simple modification:
    It worked in Debug mode but not in Release. I suspect compiler optimizations to remove the unused variable assignment. To make it work even in Release mode, I've added a function call.
    So, my solution was to add the following line anywhere in the test project:

    var bugFix = typeof(System.Data.Entity.SqlServer.SqlProviderServices).ToString();

  6. Solves my issue at step 1! Thanks for the explanation.


    I had encountered exactly the same problem on my CI build server (running Bamboo), which doesn't install any Visual Studio IDE on it.

    Without making any code changing for the build/test process (which I don't think is good solution), the best way is to copy the EntityFramework.SqlServer.dll and paste it to C:\Program Files (x86)\Microsoft Visual Studio 12.0\Common7\IDE. (where your mstest running)

    Problem solved!


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