Why is Entity Framework 6.1.3 throwing a “Could no

问题:

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()

回答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

回答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.

回答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

回答4:

In my case when I got this error, I was not able to find EF in GAC. So nothing was to unistall.

However, after investigating all EF references in all projects of the solution it was found that one of the project referenced EF 6.1.1 and all others 6.1.3. Answer by michaelhawkins helped in this case, I removed all EF from all projects and then installed the same latest version back.

Just leaving it here, because in all cases this exception most probably is due to conflict of versions of EF, but where specifically you need to look to resolve the conflict may depend on various factors.

回答5:

In my case I had to remove the EntityFramework.dll from this folder:

C:\Windows\Microsoft.NET\assembly\GAC_MSIL\EntityFramework

回答6:

The same problem happened to me

Open Visual Studio --> Tools --> Extensions and Updates

1. Check Updates first if any update related with Nuget Package Manager Console update it.

2. Select All tab in Extensions and Updates be sure your Nuget Package Manager Console version

3. Open your project folder --> Packages then delete everything about entityframework

4. If there is a file like entityframework.deleteme --> delete it and restart Visual Studio

回答7:

For future reference in my case removing EntityFramework.SqlServer from GAC fixed this error. The assembly was exactly same version than the one referenced in my application (6.0.0.0 for both EntityFramework.dll and EntityFramework.SqlServer.dll). However, I didn't have EntityFramework in GAC when this exception occurred.

I had installed the EntityFramework references to my application with SQLite Core (x86/x64) using NuGet. Also I had dabbled with GAC a bit previously and most likely added the assembly there myself.

回答8:

Do you have EntityFramework.SqlServer referenced? This should come automatically with entity framework. If not try add it as a reference, or via Nuget.

Ofcourse that is if you are usign SqlServer provider. if not, you need to add your specific provider.

回答9:

Just update the package.config file to match the EF version your using In this case, it is "6.1.3".

回答10:

I was getting this same error after installing Visual Studio 2015 (VS 2015) when running unit tests that use SQL CE. My connection factory is SqlCeConnectionFactory and provider is System.Data.Entity.SqlServerCompact.SqlCeProviderServices, EntityFramework.SqlServerCompact.

The solution for me was to add the path to EntityFramework.SqlServerCompact.dll to the deployment list in my .testsettings file. The line I added looks like this:

<DeploymentItem filename="packages\EntityFramework.SqlServerCompact.6.1.1\lib\net45\EntityFramework.SqlServerCompact.dll" />

回答11:

Changing connectionstring value from

"data source=.;initial catalog=[dbname];integrated security=True"

To

"Server=.;Database=[dbname];integrated security=True"