Give more detailed information when assemblies fail to load

@gkhanna79

I'm running into a problem:

Unhandled Exception: System.IO.FileLoadException: Could not load file or assembly 'System.Runtime.CompilerServices.Unsafe, Version=4.0.3.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)

It would be great if this exception could tell me:

What version of System.Runtime.CompilerServices.Unsafe was referenced
What assembly referencing System.Runtime.CompilerServices.Unsafe triggered the load
What the version of the reference to System.Runtime.CompilerServices.Unsafe is that is causing the mismatch.

Bonus Points

Where the assembly was loaded on disk if it is on disk (though I can get this from the modules window in VS).

That would save me so much time....

/cc @gkhanna79

Agreed this causes nightmares when it happens in production

Worse case is below, which dependent library couldn't load, never know:
System.IO.FileNotFoundException: Could not load file or assembly 'ServiceFabricServiceModel, Version=5.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies.

I've been hitting issues like this, too. I found that binding redirects weren't being correctly set despite my best efforts to have them generated. I solved the issues for myself using some ~~duct tape~~ PowerShell + ReGex, like so:
From the output directory:

Get-ChildItem | ? { $_.Extension -eq '.dll' } | % { [System.Reflection.AssemblyName]::GetAssemblyName($_.FullName).FullName }

Then with that list of "binaries which are actually present at runtime", search/replace:
Find: ([^,]+), Version=([^,]+), Culture=neutral, PublicKeyToken=(.*)
Replace:

<dependentAssembly>
  <assemblyIdentity name="\1" publicKeyToken="\3" culture="neutral" />
  <bindingRedirect oldVersion="0.0.0.0-\2" newVersion="\2" />
</dependentAssembly>

Tooling could ease this, and better exception messages really would make our lives easier, but if anyone is hitting errors like these, that was my makeshift workaround.

In full Desktop, I enable Fusion logging for failures on all development and QA machines, and occasionally for onsite customer support as well. I know that Core does not have Fusion, but enabling a similar logging for load failures would be a great help. Of course some changes such as configuration would need to be done outside of the registry, though.

Yeah, The same code

assembly = AssemblyLoadContext.Default.LoadFromAssemblyPath(file.FullName);

Before upgrading to 1.1, I got the error "Assembly with same name is already loaded" which is nice.

After 1.1, I got "System.IO.FileLoadException: Could not load file or assembly 'SimplCommerce.Infrastructure, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'.\r\n at System.Runtime.Loader.AssemblyLoadContext.LoadFromPath(IntPtr ptrNativeAssemblyLoadContext, String ilPath, String niPath, ObjectHandleOnStack retAssembly)\r\n at System.Runtime.Loader.AssemblyLoadContext.LoadFromAssemblyPath(String assemblyPath)\r\n at SimplCommerce.WebHost.Extensions.ServiceCollectionExtensions.LoadInstalledModules(IServiceCollection services, IList`1 modules, IHostingEnvironment hostingEnvironment) in C:\DATA\Projects\SimplCommerce\SimplCommerce\src\SimplCommerce.WebHost\Extensions\ServiceCollectionExtensions.cs:line 44".
I don't know what going on, very confused. But then I try to get loaded assembly

assembly = Assembly.Load(new AssemblyName(Path.GetFileNameWithoutExtension(file.Name)));

It work the same as before.
The full source code can be found at https://github.com/simplcommerce/SimplCommerce/blob/master/src/SimplCommerce.WebHost/Extensions/ServiceCollectionExtensions.cs

We've added detailed tracing for this: https://docs.microsoft.com/en-us/dotnet/core/dependency-loading/collect-details

It's not as convenient as exception message, but it provides more detail than could fit into exception message. We hope it can be used for at least the same scenarios as fusion logging was used in .NET Framework.

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Give more detailed information when assemblies fail to load #7051

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Give more detailed information when assemblies fail to load #7051

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Drawaes commented on Nov 24, 2016

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