Mismatch in assembly versioning? (.Net Core 2.0 with .NET Standard 2 class library)

Question

So my solution compiles but when I run it I get an error in the class library that is running .NET 4.6.1.

System.TypeLoadException: 'Could not load type 'System.Data.Common.DbProviderFactories' from assembly 'System.Data, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'.

Any suggestions?

EDIT:

Complete error:

$exception {System.TypeLoadException: Could not load type 'System.Data.Common.DbProviderFactories' from assembly 'System.Data, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'. at System.Data.Entity.Infrastructure.DependencyResolution.DefaultProviderFactoryResolver.GetService(Type type, Object key, Func3 handleFailedLookup) at System.Data.Entity.Infrastructure.DependencyResolution.DefaultProviderFactoryResolver.GetServices(Type type, Object key) at System.Collections.Concurrent.ConcurrentDictionary2.GetOrAdd(TKey key, Func2 valueFactory) at System.Linq.Enumerable.SelectManySingleSelectorIterator2.MoveNext() at System.Linq.Enumerable.ConcatIterator1.MoveNext() at System.Linq.Enumerable.SelectManySingleSelectorIterator2.MoveNext() at System.Linq.Enumerable.ConcatIterator1.MoveNext() at System.Linq.Enumerable.<OfTypeIterator>d__321.MoveNext() at System.Collections.Generic.List1.AddEnumerable(IEnumerable1 enumerable) at System.Linq.Enumerable.ToList[TSource](IEnumerable1 source) at System.Data.Entity.Infrastructure.DependencyResolution.InternalConfiguration.Lock() at System.Data.Entity.Infrastructure.DependencyResolution.DbConfigurationManager.<.ctor>b__1() at System.Lazy1.ViaFactory(LazyThreadSafetyMode mode) at System.Lazy1.ExecutionAndPublication(LazyHelper executionAndPublication, Boolean useDefaultConstructor) at System.Lazy1.CreateValue() at System.Data.Entity.Infrastructure.DependencyResolution.DbConfigurationManager.GetConfiguration() at System.Data.Entity.DbContext.InitializeLazyInternalContext(IInternalConnection internalConnection, DbCompiledModel model) at X.Y.ConfigurationModule.ConfigurationContainer..ctor(String nameOrConnectionString)} System.TypeLoadException

Are you referencing System.Data.Common.DbProviderFactories?

user5093161
– user5093161

2017-10-18 10:54:50 +00:00
Commented Oct 18, 2017 at 10:54 — user5093161
– user5093161, Commented Oct 18, 2017 at 10:54

score 1 · Accepted Answer · 2017-10-18 11:08:11Z

1

You see this type of errors when the assembly your are using is different from the reference assembly.

Example

In this condition you see this error because first one using version 3 and other using 2

Please do these check

1:Open references right click on System.Data.Common.DbProviderFactories assembly and check its version

2:Now open you package config or app config file and check the version of that assembly there.

Solution

If versions conflict please install the library from

https://www.nuget.org/packages/System.Data.Common/

Then go to bin folder delete the 'System.Data.Common.DbProviderFactories' dll also delete it from references from your project then click add references go to packages folder because the latest library you downloaded goes in this folder so just add reference. Now right click on this assembly and copy version name and paste that version in your appconfig or packages config file.

edited Oct 18, 2017 at 11:08

answered Oct 18, 2017 at 11:00

user5093161

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7 Comments

Lars Thorén Over a year ago

Thanks for the reply. I have not referenced any assembly explicitly. I have tried to get System.Data.Common from Nuget but having tried the different versions in the nuget package has not helped. It seems no matter what I try the error msg remains the same. It refers to version 4.0.0.0 which was never a version being used. Could the error be with System.Data and not System.Data.Common, then 4.0.0.0 would make more sense.

user5093161 Over a year ago

So are you still facing the same problem?

Lars Thorén Over a year ago

Yes the problem remains the same. The error says: "from assembly System.Data" so maybe there was never anything wrong with System.Data.Common?

Lars Thorén Over a year ago

Could be as easy as DbProviderFactories class not being available in .NET Standard 2.0, found this: github.com/dotnet/standard/issues/356

gorillapower Over a year ago

I have the same issue, was it resolved or must we wait for core 2.1?

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