Could not load file or assembly 'Microsoft.Extensions.DependencyInjection.Abstractions using COM [duplicate]

Question

[Recent Note]

If it were not for the com-visible aspect, this question would be a duplicate of this question on assembly binding. I had struggled for days because I did not realize that I needed to alter my unit test project as well as the com visible project. If you don't want to read through my struggles realizing this, skip to the last update.

[Pre-amble]

I feared it may be a bridge to far trying to access a dotnet standard 2.0 library from VB6 via a COM Visible Framework 4.7.2 library, but wanted to try.

Hello World does work. ( i.e calling a simple function that returns a string )

However I get this error when I try and run the VB6 program via the IDE or as a .EXE.

The error message indicates the problem is occuring in the code of the c# dotnet standard2.0 library.

System.IO.FileNotFoundException: Could not load file or assembly 'Microsoft.Extensions.DependencyInjection.Abstractions, 
Version=3.1.0.0, Culture=neutral, 
PublicKeyToken=adb9793829ddae60' or one of its dependencies. 
The system cannot find the file specified.
File name: 'Microsoft.Extensions.DependencyInjection.Abstractions, Version=3.1.0.0,
Culture=neutral, PublicKeyToken=adb9793829ddae60'
at Microsoft.EntityFrameworkCore.Internal.ServiceProviderCache.<>c__DisplayClass4_0.<GetOrAdd>g__BuildServiceProvider|3()
at Microsoft.EntityFrameworkCore.Internal.ServiceProviderCache.<>c__DisplayClass4_0.<GetOrAdd>b__2(Int64 k)
at System.Collections.Concurrent.ConcurrentDictionary`2.GetOrAdd(TKey key, Func`2 valueFactory)
at Microsoft.EntityFrameworkCore.Internal.ServiceProviderCache.GetOrAdd(IDbContextOptions options, Boolean providerRequired)
at Microsoft.EntityFrameworkCore.DbContext..ctor(DbContextOptions options)
at SBDSTD.Standard.Entities.ApiDbContext..ctor(DbContextOptions options)
at SBDSTD.Standard.Services.Helper.MakeContext(String connectionString)

The library code where the error is occurs is

public static ApiDbContext MakeContext(string connectionString)
{
       var optionsBuilder = new DbContextOptionsBuilder<ApiDbContext>();
       optionsBuilder.UseSqlServer(connectionString );
       var options = optionsBuilder.Options;
       return new ApiDbContext(options); // Error occurs here
}

The context class contains

public class ApiDbContext : DbContext
{
    public ApiDbContext(DbContextOptions<ApiDbContext> options)
        : base(options)
    {
    }
 // etc

I managed to work around the issue by creating a Framework console exe , then getting vb6 to shell out to it.

Dim num As Long
num = ShellSync(cmd, vbMinimizedNoFocus)

Where code for shellsync is in a module

Option Explicit
Private Const INFINITE = &HFFFFFFFF
Private Const SYNCHRONIZE = &H100000
Private Const PROCESS_QUERY_INFORMATION = &H400&

Private Declare Function CloseHandle Lib "kernel32" ( _
    ByVal hObject As Long) As Long

Private Declare Function GetExitCodeProcess Lib "kernel32" ( _
    ByVal hProcess As Long, _
    lpExitCode As Long) As Long

Private Declare Function OpenProcess Lib "kernel32" ( _
    ByVal dwDesiredAccess As Long, _
    ByVal bInheritHandle As Long, _
    ByVal dwProcessId As Long) As Long

Private Declare Function WaitForSingleObject Lib "kernel32" ( _
    ByVal hHandle As Long, _
    ByVal dwMilliseconds As Long) As Long

Public Function ShellSync( _
    ByVal PathName As String, _
    ByVal WindowStyle As VbAppWinStyle) As Long
    'Shell and wait.  Return exit code result, raise an
    'exception on any error.
    Dim lngPid As Long
    Dim lngHandle As Long
    Dim lngExitCode As Long

    lngPid = Shell(PathName, WindowStyle)
    If lngPid <> 0 Then
        lngHandle = OpenProcess(SYNCHRONIZE _
                             Or PROCESS_QUERY_INFORMATION, 0, lngPid)
        If lngHandle <> 0 Then
            WaitForSingleObject lngHandle, INFINITE
            If GetExitCodeProcess(lngHandle, lngExitCode) <> 0 Then
                ShellSync = lngExitCode
                CloseHandle lngHandle
            Else
                CloseHandle lngHandle
                Err.Raise &H8004AA00, "ShellSync", _
                          "Failed to retrieve exit code, error " _
                        & CStr(Err.LastDllError)
            End If
        Else
            Err.Raise &H8004AA01, "ShellSync", _
                      "Failed to open child process"
        End If
    Else
        Err.Raise &H8004AA02, "ShellSync", _
                  "Failed to Shell child process"
    End If
End Function

Interestingly if I call shell instead of shellsync I get the error

System.Exception: kg1System.IO.FileNotFoundException: Could not load file or assembly 'System.Threading.Tasks.Extensions, Version=4.2.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51' or one of its dependencies. The system cannot find the file specified.
File name: 'System.Threading.Tasks.Extensions, Version=4.2.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51'
   at SBDSTD.Standard.Helpers.LogHelper.LogMessage(String message, 

[Update]

I added the following to my code to the com visible library

    [DispId(2)]
    [ComVisible(true)]
    public string ReferenceCheck()
    {
        var factory = new Microsoft.Extensions.DependencyInjection.DefaultServiceProviderFactory();
        return "";
    }

but it did not help.

I tried to use Fuslogvw but the log viewer is empty, even after I change the settings to Log in exception text and attempt to troubleshoot

I tried using Procmon and can see the following sort of thing

I also tried to find the Modules window from the Debug menu but dont see it.

Checking This link

[Update]

I notice I have assembly binding logging turned off.

But when I look in RegEdit it is already 1

[Update]

After reading Hans Passant's comment In the com visible library I added some code to resolve assemblies

My test method in the com visible library shows the following error information.

System.TypeInitializationException: 
The type initializer for 'Microsoft.Data.SqlClient.TdsParser' 
threw an exception. ---> 
System.TypeInitializationException: 
The type initializer for 'Microsoft.Data.SqlClient.SNILoadHandle' threw an exception. 
---> System.TypeInitializationException: 
The type initializer for 'Microsoft.Data.SqlClient.SNINativeMethodWrapper' threw an exception. ---> 
System.ComponentModel.Win32Exception: Failed to load C:\Dev2\UnitTestProjectStandard\bin\Debug\x86\SNI.dll ---> System.ComponentModel.Win32Exception: 
The specified module could not be found
  Stack Trace: 
    SNINativeMethodWrapper.cctor() line 64
    --- End of inner exception stack trace ---
    SNINativeMethodWrapper.SNIInitialize()
    SNILoadHandle.ctor() line 36
    SNILoadHandle.cctor() line 17
    --- End of inner exception stack trace ---
    TdsParser.cctor() line 166
    --- End of inner exception stack trace ---
    DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection) line 1411
    DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection) line 1310
    DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal oldConnection, DbConnectionInternal& connection) line 357
    DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions) line 773
    DbConnectionClosed.TryOpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions) line 72
    SqlConnection.TryOpenInner(TaskCompletionSource`1 retry) line 1860
    SqlConnection.TryOpen(TaskCompletionSource`1 retry) line 1853
    SqlConnection.Open() line 1421
    RelationalConnection.OpenDbConnection(Boolean errorsExpected)
    RelationalConnection.Open(Boolean errorsExpected)
    RelationalCommand.ExecuteReader(RelationalCommandParameterObject parameterObject)
    Enumerator.InitializeReader(DbContext _, Boolean result)
    SqlServerExecutionStrategy.Execute[TState,TResult](TState state, Func`3 operation, Func`3 verifySucceeded)
    Enumerator.MoveNext()
    Enumerable.SingleOrDefault[TSource](IEnumerable`1 source)
    lambda_method(Closure , QueryContext )
    QueryCompiler.Execute[TResult](Expression query)
    EntityQueryProvider.Execute[TResult](Expression expression)
    Queryable.FirstOrDefault[TSource](IQueryable`1 source)

[Update]

This issue on GitHub seems related

I tried reinstalling the c** redistributable

[Update]

I finally got Fuslogvw to work with the help of this question

Which references 2 versions of the problem library.

I also noticed that my standard library has an analyzer complaining

0} is an internal API that supports the Entity Framework Core infrastructure and not subject to the same compatibility standards as public APIs. It may be changed or removed without notice in any release.

[Update]

If I make a .exe in my com visible framework project, and run it , there is no problem. The problem occurs if I try a unit test.

Fusion log shows the following

   *** Assembly Binder Log Entry  (02-Mar-20 @ 7:54:23 AM) ***

The operation failed.
Bind result: hr = 0x80131040. No description available.

Assembly manager loaded from:  C:\Windows\Microsoft.NET\Framework\v4.0.30319\clr.dll
Running under executable  C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\Common7\IDE\Extensions\TestPlatform\testhost.x86.exe
--- A detailed error log follows. 

=== Pre-bind state information ===
LOG: DisplayName = Microsoft.Extensions.DependencyInjection.Abstractions, Version=3.1.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60
 (Fully-specified)
LOG: Appbase = file:///C:/Dev2/Combridge/SBD.ComBridge/UnitTestProject1/bin/Debug
LOG: Initial PrivatePath = NULL
LOG: Dynamic Base = NULL
LOG: Cache Base = NULL
LOG: AppName = NULL
Calling assembly : Microsoft.Extensions.DependencyInjection, Version=3.1.2.0, Culture=neutral, PublicKeyToken=adb9793829ddae60.
===
LOG: This bind starts in default load context.
LOG: Using application configuration file: C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\Common7\IDE\Extensions\TestPlatform\testhost.x86.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: Post-policy reference: Microsoft.Extensions.DependencyInjection.Abstractions, Version=3.1.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60
LOG: GAC Lookup was unsuccessful.
LOG: Attempting download of new URL file:///C:/Dev2/Combridge/SBD.ComBridge/UnitTestProject1/bin/Debug/Microsoft.Extensions.DependencyInjection.Abstractions.DLL.
LOG: Assembly download was successful. Attempting setup of file: C:\Dev2\Combridge\SBD.ComBridge\UnitTestProject1\bin\Debug\Microsoft.Extensions.DependencyInjection.Abstractions.dll
LOG: Entering run-from-source setup phase.
LOG: Assembly Name is: Microsoft.Extensions.DependencyInjection.Abstractions, Version=3.1.2.0, Culture=neutral, PublicKeyToken=adb9793829ddae60
WRN: Comparing the assembly name resulted in the mismatch: Build Number
ERR: The assembly reference did not match the assembly definition found.
ERR: Run-from-source setup phase failed with hr = 0x80131040.
ERR: Failed to complete setup of assembly (hr = 0x80131040). Probing terminated.

*** Assembly Binder Log Entry  (02-Mar-20 @ 7:54:23 AM) ***

The operation failed.
Bind result: hr = 0x80131040. No description available.

Assembly manager loaded from:  C:\Windows\Microsoft.NET\Framework\v4.0.30319\clr.dll
Running under executable  C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\Common7\IDE\Extensions\TestPlatform\testhost.x86.exe
--- A detailed error log follows. 

=== Pre-bind state information ===
LOG: DisplayName = Microsoft.Extensions.DependencyInjection.Abstractions, Version=3.1.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60
 (Fully-specified)
LOG: Appbase = file:///C:/Dev2/Combridge/SBD.ComBridge/UnitTestProject1/bin/Debug
LOG: Initial PrivatePath = NULL
LOG: Dynamic Base = NULL
LOG: Cache Base = NULL
LOG: AppName = NULL
Calling assembly : Microsoft.Extensions.DependencyInjection, Version=3.1.2.0, Culture=neutral, PublicKeyToken=adb9793829ddae60.
===
LOG: This bind starts in default load context.
LOG: Using application configuration file: C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\Common7\IDE\Extensions\TestPlatform\testhost.x86.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: Post-policy reference: Microsoft.Extensions.DependencyInjection.Abstractions, Version=3.1.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60
LOG: GAC Lookup was unsuccessful.
LOG: Attempting download of new URL file:///C:/Dev2/Combridge/SBD.ComBridge/UnitTestProject1/bin/Debug/Microsoft.Extensions.DependencyInjection.Abstractions.DLL.
LOG: Assembly download was successful. Attempting setup of file: C:\Dev2\Combridge\SBD.ComBridge\UnitTestProject1\bin\Debug\Microsoft.Extensions.DependencyInjection.Abstractions.dll
LOG: Entering run-from-source setup phase.
LOG: Assembly Name is: Microsoft.Extensions.DependencyInjection.Abstractions, Version=3.1.2.0, Culture=neutral, PublicKeyToken=adb9793829ddae60
WRN: Comparing the assembly name resulted in the mismatch: Build Number
ERR: The assembly reference did not match the assembly definition found.
ERR: Run-from-source setup phase failed with hr = 0x80131040.
ERR: Failed to complete setup of assembly (hr = 0x80131040). Probing terminated.

I note some version differences!

I tried running the test on a different machine with VS 16.4.4 in case it was an issue with the Preview version of Visual Studio, however the problem was repeated.

In my framework test project I tried installing the 3.1.1 version of Microsoft.Extensions.DependencyInjectionAbstractions and noticed a warning

Severity    Code    Description Project File    Line    Suppression State
Warning NU1605  Detected package downgrade: Microsoft.Extensions.DependencyInjection.Abstractions from 3.1.2 to 3.1.1. Reference the package directly from the project to select a different version. 
 UnitTestProject1 -> SBD.CombridgeVivadStd -> SBDSTD.Standard 1.0.0-CI-20200301-211054 -> Microsoft.EntityFrameworkCore 3.1.2 -> Microsoft.Extensions.DependencyInjection 3.1.2 -> Microsoft.Extensions.DependencyInjection.Abstractions (>= 3.1.2) 
 UnitTestProject1 -> Microsoft.Extensions.DependencyInjection.Abstractions (>= 3.1.1)   UnitTestProject1    C:\Dev2\Combridge\SBD.ComBridge\UnitTestProject1\UnitTestProject1.csproj    1   

I retried Simon's advice to install microsoft.data.sqlclient.sni manually

but still got the error

Could not load file or assembly 'Microsoft.Extensions.DependencyInjection.Abstractions, Version=3.1.0.0

I also tried downloading the 1.1.1 version of microsoft.data.sqlclient.sni

[Update] I decided to try rolling back entity framework in the .netstandard2.0 project to use

 <PackageReference Include="Microsoft.EntityFrameworkCore" Version="3.1.0" />
 <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="3.1.0" />

Now when I unit test with the com visible framework project I get

 System.Exception: vivadbridgestd:GetValidCarriers line: 20 error:System.Exception: kg1System.IO.FileLoadException: Could not load file or assembly 'System.ComponentModel.Annotations, Version=4.2.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)
    File name: 'System.ComponentModel.Annotations, Version=4.2.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'
       at Microsoft.EntityFrameworkCore.Metadata.Conventions.Infrastructure.RelationalConventionSetBuilder.CreateConventionSet()
       at Microsoft.EntityFrameworkCore.Metadata.Conventions.SqlServerConventionSetBuilder.CreateConventionSet()
       at Microsoft.EntityFrameworkCore.Metadata.Conventions.Internal.RuntimeConventionSetBuilder.CreateConventionSet()
       at Microsoft.EntityFrameworkCore.Infrastructure.ModelSource.CreateModel(DbContext context, IConventionSetBuilder conventionSetBuilder)
       at Microsoft.EntityFrameworkCore.Infrastructure.ModelSource.GetModel(DbContext context, IConventionSetBuilder conventionSetBuilder)
       at Microsoft.EntityFrameworkCore.Internal.DbContextServices.CreateModel()
       at Microsoft.EntityFrameworkCore.Internal.DbContextServices.get_Model()
       at Microsoft.EntityFrameworkCore.Infrastructure.EntityFrameworkServicesBuilder.<>c.<TryAddCoreServices>b__7_3(IServiceProvider p)
       at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitFactory(FactoryCallSite factoryCallSite, RuntimeResolverContext context)
       at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSiteMain(ServiceCallSite callSite, TArgument argument)
       at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitCache(ServiceCallSite callSite, RuntimeResolverContext context, ServiceProviderEngineScope serviceProviderEngine, RuntimeResolverLock lockType)
       at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScopeCache(ServiceCallSite singletonCallSite, RuntimeResolverContext context)
       at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(ServiceCallSite callSite, TArgument argument)
       at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, RuntimeResolverContext context)
       at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSiteMain(ServiceCallSite callSite, TArgument argument)
       at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitCache(ServiceCallSite callSite, RuntimeResolverContext context, ServiceProviderEngineScope serviceProviderEngine, RuntimeResolverLock lockType)
       at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScopeCache(ServiceCallSite singletonCallSite, RuntimeResolverContext context)
       at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(ServiceCallSite callSite, TArgument argument)
       at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.Resolve(ServiceCallSite callSite, ServiceProviderEngineScope scope)
       at Microsoft.Extensions.DependencyInjection.ServiceLookup.DynamicServiceProviderEngine.<>c__DisplayClass1_0.<RealizeService>b__0(ServiceProviderEngineScope scope)
       at Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngine.GetService(Type serviceType, ServiceProviderEngineScope serviceProviderEngineScope)
       at Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngineScope.GetService(Type serviceType)
       at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService(IServiceProvider provider, Type serviceType)
       at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService[T](IServiceProvider provider)
       at Microsoft.EntityFrameworkCore.DbContext.get_DbContextDependencies()
       at Microsoft.EntityFrameworkCore.DbContext.get_InternalServiceProvider()
       at Microsoft.EntityFrameworkCore.DbContext.get_DbContextDependencies()
       at Microsoft.EntityFrameworkCore.DbContext.get_Model()
       at Microsoft.EntityFrameworkCore.Internal.InternalDbSet`1.get_EntityType()
       at Microsoft.EntityFrameworkCore.Internal.InternalDbSet`1.get_EntityQueryable()
       at Microsoft.EntityFrameworkCore.Internal.InternalDbSet`1.System.Linq.IQueryable.get_Provider()
       at System.Linq.Queryable.SingleOrDefault[TSource](IQueryable`1 source, Expression`1 predicate)
       at SBDSTD.Standard.Helpers.LogHelper.InnerLogMessage(String message, JobHeaderLogInfo logInfo, Boolean sendEmail, ApiDbContext connect)

This causes my exe to fail as well.

Then I tried the 3.1.0 version of EFCore I now get the following in the framework test project

Test method UnitTestProject1.UnitTest1.T225_ValidCarriers threw exception: 
System.Exception: vivadbridgestd:GetValidCarriers line: 20 error:System.Exception: kg1System.Exception: Line 53 System.IO.FileLoadException: Could not load file or assembly 'Microsoft.Extensions.DependencyInjection.Abstractions, Version=3.1.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)
File name: 'Microsoft.Extensions.DependencyInjection.Abstractions, Version=3.1.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60'
   at Microsoft.EntityFrameworkCore.Internal.ServiceProviderCache.<>c__DisplayClass4_0.<GetOrAdd>g__BuildServiceProvider|3()
   at Microsoft.EntityFrameworkCore.Internal.ServiceProviderCache.<>c__DisplayClass4_0.<GetOrAdd>b__2(Int64 k)
   at System.Collections.Concurrent.ConcurrentDictionary`2.GetOrAdd(TKey key, Func`2 valueFactory)
   at Microsoft.EntityFrameworkCore.Internal.ServiceProviderCache.GetOrAdd(IDbContextOptions options, Boolean providerRequired)
   at Microsoft.EntityFrameworkCore.DbContext..ctor(DbContextOptions options)
   at SBDSTD.Standard.Entities.ApiDbContext..ctor(DbContextOptions`1 options)
   at SBDSTD.Standard.Services.Helper.MakeContext(String connectionString)

Assembly manager loaded from:  C:\Windows\Microsoft.NET\Framework\v4.0.30319\clr.dll
Running under executable  C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\Common7\IDE\Extensions\TestPlatform\testhost.x86.exe
--- A detailed error log follows. 

=== Pre-bind state information ===
LOG: DisplayName = Microsoft.Extensions.DependencyInjection.Abstractions, Version=3.1.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60
 (Fully-specified)
LOG: Appbase = file:///C:/Dev2/Combridge/SBD.ComBridge/UnitTestProject1/bin/Debug
LOG: Initial PrivatePath = NULL
Calling assembly : Microsoft.Extensions.DependencyInjection, Version=3.1.1.0, Culture=neutral, PublicKeyToken=adb9793829ddae60.
===
LOG: This bind starts in default load context.
LOG: Using application configuration file: C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\Common7\IDE\Extensions\TestPlatform\testhost.x86.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: Post-policy reference: Microsoft.Extensions.DependencyInjection.Abstractions, Version=3.1.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60
LOG: Attempting download of new URL file:///C:/Dev2/Combridge/SBD.ComBridge/UnitTestProject1/bin/Debug/Microsoft.Extensions.DependencyInjection.Abstractions.DLL.
WRN: Comparing the assembly name resulted in the mismatch: Build Number
ERR: Failed to complete setup of assembly (hr = 0x80131040). Probing terminated.

   at SBDSTD.Standard.Services.Helper.MakeContext(String connectionString)

also happening in the .exe

I wondered if this question about entityframework.core is related but I can only find Microsoft.EntityFrameworkCore on Nuget.

[Update unit test now works]

I now have my unit test working. I needed to include the following near the top of the unit test project

   <PropertyGroup>
    <AutoGenerateBindingRedirects>true</AutoGenerateBindingRedirects>
    <GenerateBindingRedirectsOutputType>true</GenerateBindingRedirectsOutputType>    
   </PropertyGroup>

As discussed in this question on assembly binding

However I still need to a work around to use my com visible library in VB6

Surveying

checking the solution for #34772664 – Surveying

#19774655 – Surveying

I've got plenty of C# code running through COM from C# so I think this should be solvable. For some reason Microsoft.Extensions.DependencyInjection.Abstractions doesn't get loaded even though other .NET dependencies are loaded. Any chance that DLL has 64 bit code? Is it in the GAC? – Harman

As a test, you could add Microsoft.Extensions.DependencyInjection.Abstractions as an explicit reference in your COM visible project & see if that helps. And/or mark it copy local (unless it is in the GAC). – Harman

Another thought, bring up the Modules window in Visual Studio and when the exception occurs (or just before) see what assemblies are loaded. Presumably the DI one will not be, but possibly this will give some other clue. – Harman

@UuDdLrLrSs No joy addint the library as an explicit reference in the com visible project. Not sure how to mark it and copy local as I am using PackageReference. (The reference shows a blue icon in VS2019) How do I access the modules window in VS? Do you mean VB6 ide Visual Studio? – Surveying

never the less I manually copied it local. No joy with that either. I notice that there is a x64 and an x86 folder containing SNI.dll – Surveying

Modules should be one of the windows you can open from Debug menu > Windows submenu – Harman

Does either the exception you receive or its InnerException have a FusionLog property that contains anything relevant? – Harman

Let us continue this discussion in chat. – Surveying

It is the standard DLL Hell problem, the CLR looks only a two locations for dependent assemblies. The GAC and the path where the EXE file is located, neither have that file. The location where the [ComVisible] assembly lives is not searched. Of the three standard solutions, two don't qualify because this is a .NETStandard assembly. One left, you need AppDomain.AssemblyResolve going. Tends to require a God interface so you can subscribe the event soon enough, one that the client code has to create first, similar to Application as used in Office interop. – Edgerton

github.com/dotnet/SqlClient/issues/211 – Surveying

Have you tried to download nuget.org/packages/Microsoft.Data.SqlClient.SNI unzip it and copy the sni.dll manually? – Calcification

@SimonMourier Thank you, I just tried it. no joy. – Surveying

Did you try to expose a .NET Core 3+ library via COM following microsoft's guide? learn.microsoft.com/en-us/dotnet/core/native-interop/… – Buffalo

@MartinUllrich I need my library to be accessible by both .netcore and vb6, thus I thought I needed my library to be.netstandard2.0 ~#60541220 – Surveying

Answer 1

I've been struggling with exactly the same problem and was able to solve it.

In my case the problem DLL was Microsoft.Extensions.Logging. Here's my exception:

Could not load file or assembly 'System.IO.FileNotFoundException: Could not load file or assembly 'Microsoft.Extensions.Logging, 
Version=2.2.0.0, Culture=neutral, 
PublicKeyToken=adb9793829ddae60' or one of its dependencies. 
The system cannot find the file specified.

The solution was insanely simple, basically app.config works for your VB6 EXE that is consuming COM exposed .NET classes. You just need to create a regular app.config with your <assemblyBinding> tags and it will work. The tricky part is where to place this config and how to name it.

1. When you run your EXE from IDE (VB6) create VB6.exe.config in C:\Program Files (x86)\Microsoft Visual Studio\VB98. Don't forget to restart the IDE after you created the config.
2. When you run from EXE directly create ExeName.exe.config in the same folder as your ExeName.exe

Here's the Fusion log on how it resolves the redirection after the change (run from IDE case):

Calling assembly : Unity.Microsoft.Logging, Version=5.11.1.0, Culture=neutral, PublicKeyToken=489b6accfaf20ef0.
===
LOG: This bind starts in LoadFrom load context.
WRN: Native image will not be probed in LoadFrom context. Native image will only be probed in default load context, like with Assembly.Load().
LOG: Using application configuration file: C:\Program Files (x86)\Microsoft Visual Studio\VB98\VB6.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: Redirect found in application configuration file: 2.2.0.0 redirected to 5.0.0.0.
LOG: Post-policy reference: Microsoft.Extensions.Logging, Version=5.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60
LOG: Binding succeeds. Returns assembly from C:\Program Files (x86)\Retail\Common\Microsoft.Extensions.Logging.dll.
LOG: Assembly is loaded in LoadFrom load context.

Burma