Why is Entity Framework 6.1.3 throwing a "Could not load type 'System.Data.Entity.Infrastructure.TableExistenceChecker'"

Question

Brand new project and entity framework will not start due to the exception being thrown as soon as the context instance is created.

Entity framework throws the following exception:

Could not load type 'System.Data.Entity.Infrastructure.TableExistenceChecker' from assembly 'EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'.

References:

• EntityFramework
• EntityFramework.SqLServer

Via the nuget package manager:

Install-Package entityframework

Very simple context and entity:

public class TextDbContext : DbContext
{
    public TextDbContext()
        : base("Test")
    {
    }

    public DbSet<TestEntity> TestEntity { get; set; }
}

public class TestEntity
{
    public int Id { get; set; } 
    public string Name { get; set; }
}

static void Main(string[] args)
{
    var test = ConfigurationManager.ConnectionStrings["Test"].ConnectionString;

    using (var conn = new SqlConnection(test))
    {
        conn.Open();
        var cmd = new SqlCommand("Select * from testtable", conn);
        var result = cmd.ExecuteReader();
    }
    //exception thrown on this line is the same as the one in the context
    var instance = SqlProviderServices.Instance;

    using (var db = new TextDbContext())
    {
         var item = new TestEntity
         {
             Name = "xyz"
         };
         db.TestEntity.Add(item);
         db.SaveChanges();
    }
}

Here is the current app.config file:

<?xml version="1.0" encoding="utf-8"?>
<configuration>
    <configSections>
        <section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=6.0.0.0, Culture=neutral,  PublicKeyToken=b77a5c561934e089" requirePermission="false" />
    </configSections>
    <connectionStrings>
        <add name="Test" connectionString="server=localhost;database=Test;Data Source=localhost;Integrated Security=True;Pooling=True" providerName="System.Data.SqlClient" />
    </connectionStrings>
    <startup>
       <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
    </startup>
    <entityFramework>
        <defaultConnectionFactory type="System.Data.Entity.Infrastructure.SqlConnectionFactory, EntityFramework" />
         <providers>
            <provider invariantName="System.Data.SqlClient" type="System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer" />
        </providers>
    </entityFramework>
</configuration>

Stack trace is as follows:

   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor)
   at System.Reflection.RuntimeMethodInfo.UnsafeInvokeInternal(Object obj, Object[] parameters, Object[] arguments)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at System.Reflection.RuntimePropertyInfo.GetValue(Object obj, BindingFlags invokeAttr, Binder binder, Object[] index, CultureInfo culture)
   at System.Reflection.RuntimePropertyInfo.GetValue(Object obj, Object[] index)
   at System.Data.Entity.Utilities.MemberInfoExtensions.GetValue(MemberInfo memberInfo)
   at System.Data.Entity.Infrastructure.DependencyResolution.ProviderServicesFactory.GetInstance(Type providerType)
   at System.Data.Entity.Infrastructure.DependencyResolution.ProviderServicesFactory.GetInstance(String providerTypeName, String providerInvariantName)
   at System.Data.Entity.Internal.AppConfig.<.ctor>b__2(ProviderElement e)
   at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at System.Data.Entity.Internal.AppConfig.<.ctor>b__1()
   at System.Lazy`1.CreateValue()
   at System.Lazy`1.LazyInitValue()
   at System.Lazy`1.get_Value()
   at System.Data.Entity.Internal.AppConfig.get_DbProviderServices()
   at System.Data.Entity.Infrastructure.DependencyResolution.AppConfigDependencyResolver.RegisterDbProviderServices()
   at System.Data.Entity.Infrastructure.DependencyResolution.AppConfigDependencyResolver.GetServiceFactory(Type type, String name)
   at System.Data.Entity.Infrastructure.DependencyResolution.AppConfigDependencyResolver.<>c__DisplayClass1.<GetService>b__0(Tuple`2 t)
   at System.Collections.Concurrent.ConcurrentDictionary`2.GetOrAdd(TKey key, Func`2 valueFactory)
   at System.Data.Entity.Infrastructure.DependencyResolution.AppConfigDependencyResolver.GetService(Type type, Object key)
   at System.Data.Entity.Infrastructure.DependencyResolution.DbDependencyResolverExtensions.GetServiceAsServices(IDbDependencyResolver resolver, Type type, Object key)
   at System.Data.Entity.Infrastructure.DependencyResolution.AppConfigDependencyResolver.GetServices(Type type, Object key)
   at System.Data.Entity.Infrastructure.DependencyResolution.ResolverChain.<>c__DisplayClass6.<GetServices>b__5(IDbDependencyResolver r)
   at System.Linq.Enumerable.<SelectManyIterator>d__14`2.MoveNext()
   at System.Linq.Enumerable.<ConcatIterator>d__71`1.MoveNext()
   at System.Linq.Enumerable.<OfTypeIterator>d__aa`1.MoveNext()
   at System.Data.Entity.Utilities.IEnumerableExtensions.Each[T](IEnumerable`1 ts, Action`1 action)
   at System.Data.Entity.Infrastructure.DependencyResolution.InternalConfiguration.Lock()
   at System.Data.Entity.Infrastructure.DependencyResolution.DbConfigurationManager.<.ctor>b__1()
   at System.Lazy`1.CreateValue()
   at System.Lazy`1.LazyInitValue()
   at System.Lazy`1.get_Value()
   at System.Data.Entity.Infrastructure.DependencyResolution.DbConfigurationManager.GetConfiguration()
   at System.Data.Entity.DbContext.InitializeLazyInternalContext(IInternalConnection internalConnection, DbCompiledModel model)
   at System.Data.Entity.DbContext..ctor(String nameOrConnectionString)
   at test2.TextDbContext..ctor() in \\srv\users\carl.tierney\Documents\Visual Studio 2013\Projects\test2\test2\test2context.cs:line 13
   at test2.Program.Main(String[] args) in \\srv\users\carl.tierney\Documents\Visual Studio 2013\Projects\test2\test2\Program.cs:line 13
   at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
   at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
   at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
   at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state
   at System.Threading.ThreadHelper.ThreadStart()

Answer 1

If you find as I did that EF is not installed in the Gac then the next step is to uninstall it AFTER you note the version of your package. I use NuGet so I went to Tools...Library Package Manager...Package Manager Console. I tried the GUI first but uninstalling failed and as of this writing you can only install the latest version of the package.

1. Open your solution and go to Tools...Library Package Manager...Package Manager Console
2. Select the project that uses EF and is having the problem
3. Type Uninstall-package EntityFramework
4. You should be prompted to restart Visual Studio so close and reopen VS and your solution
5. Open Package Manager Console with Tools...Library Package Manager...Package Manager Console
6. Type Install-package EntityFramework (add -Version x.x.x if you're installing an older version)
7. You should be good to go

Answer 2

I had the exact same problem in my unit test project. After a couple of hours of troubleshooting I noticed that the .csproj-file still had reference to my previous version of EF:

<Reference Include="EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089, processorArchitecture=MSIL">
    <SpecificVersion>False</SpecificVersion>
    <HintPath>..\packages\EntityFramework.6.1.1\lib\net45\EntityFramework.dll</HintPath>
</Reference>

I simply changed the version to 6.1.3 and all tests ran fine again.

Answer 3

Apparently if there is a reference to entity framework in the GAC and it is not the same as the one you have referenced via Nuget you get this error. In my case it was 6.0.0 in the GAC.

Solution:

Launch the developer command prompt for visual studio then:

gacutil -u EntityFramework