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, Func 3 handleFailedLookup) at System.Data.Entity.Infrastructure.DependencyResolution.DefaultProviderFactoryResolver.GetServices(Type type, Object key) at System.Collections.Concurrent.ConcurrentDictionary 2.GetOrAdd(TKey key, Func 2 valueFactory) at System.Linq.Enumerable.SelectManySingleSelectorIterator 2.MoveNext() at System.Linq.Enumerable.ConcatIterator 1.MoveNext() at System.Linq.Enumerable.SelectManySingleSelectorIterator 2.MoveNext() at System.Linq.Enumerable.ConcatIterator 1.MoveNext() at System.Linq.Enumerable.<OfTypeIterator>d__32 1.MoveNext() at System.Collections.Generic.List 1.AddEnumerable(IEnumerable 1 enumerable) at System.Linq.Enumerable.ToList[TSource](IEnumerable 1 source) at System.Data.Entity.Infrastructure.DependencyResolution.InternalConfiguration.Lock() at System.Data.Entity.Infrastructure.DependencyResolution.DbConfigurationManager.<.ctor>b__1() at System.Lazy 1 source) at System.Data.Entity.Infrastructure.DependencyResolution.InternalConfiguration.Lock() at System.Data.Entity.Infrastructure.DependencyResolution.DbConfigurationManager.<.ctor>b__1() at System.Lazy 1.ViaFactory(LazyThreadSafetyMode mode) at System.Lazy 1.ExecutionAndPublication(LazyHelper executionAndPublication, Boolean useDefaultConstructor) at System.Lazy 1.CreateValue() at System.Data.Entity.Infrastructure.DependencyResolution.DbConfigurationManager.GetConfiguration() at System.Data.Entity.DbContext.InitializeLazyInternalContext(IInternalConnection internalConnection, DbCompiledModel model) at XYConfigurationModule.ConfigurationContainer..ctor(String nameOrConnectionString)} System.TypeLoadException

Answer 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.