Could not load file or assembly System.Runtime.CompilerServices.Unsafe


I created a Visual Studio (Community 2019) project with C# using ServiceStack.Redis. Since it is C#, I use Windows 10 (there is a Redis version for Windows but it is really old and as I know, it is unofficial so I am afraid that might be the problem). Here is an excerpt from my code:

public class PeopleStorage: IDisposable
    public PeopleStorage()
        redisManager = new RedisManagerPool("localhost");
        redis = (RedisClient)redisManager.GetClient();
        facts = (RedisTypedClient<List<Fact>>)redis.As<List<Fact>>();

    public List<Fact> GetFacts(int id)
        string sid = id.ToString();
        if (facts.ContainsKey(sid))
            return facts[sid];
        return accessor.GetFacts(id);

    private RedisTypedClient<List<Fact>> facts;
    private RedisClient redis;
    private RedisManagerPool redisManager;

In an attempt to connect to Redis in line return facts[sid];, an exception occurs:

System.IO.FileLoadException: "Could not load file or assembly "System.Runtime.CompilerServices.Unsafe, Version=, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" or one of it's dependences. The found Assembly's manifest definition does not match the Assembly reference. (Exception from HRESULT: 0x80131040)"

(May be inaccurate as I have translated it)

I have tried updating all the packages, starting with ServiceStack packages, ending with System.Runtime.CompilerServices.Unsafe itself. Moreover, you can't choose version in NuGet, the closest one there is 4.0.0, while the relevant is 4.0.7.

I do not understand why it uses this version and how I can fix this problem.
Even a clean reinstall of Visual Studio did not help.

asked on Stack Overflow Jul 6, 2020 by Rabter • edited Jul 7, 2020 by thatguy

2 Answers


Could not load file or assembly System.Runtime.CompilerServices.Unsafe

It seems that you have installed System.Runtime.CompilerServices.Unsafe nuget package 4.5.3 version. And it corresponds to System.Runtime.CompilerServices.Unsafe.dll assembly version


1) Please try to register System.Runtime.CompilerServices.Unsafe version into GAC so that the system can it.

  • Run Developer Command Prompt for VS2019 as Administrator

  • type:

    cd xxxxx (the path of the the System.Runtime.CompilerServices.Unsafe
    gacutil /i System.Runtime.CompilerServices.Unsafe.dll

2) If you use Net Framework projects with xxx.config file, you could use bindingRedirect.

Add these in app.config file or web.config file:

      <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">  
            <assemblyIdentity name="System.Runtime.CompilerServices.Unsafe"  
                              culture="neutral" />  
            <bindingRedirect oldVersion=""  

Besides, if you update System.Runtime.CompilerServices.Unsafe nuget package version to the newer version, you should also changed the bindingRedirect assembly version.

You can refer to these assembly versions of System.Runtime.CompilerServices.Unsafe

4.5.x is System.Runtime.CompilerServices.Unsafe nuget package version while 4.0.x.x is System.Runtime.CompilerServices.Unsafe.dll assembly version.

4.5.0 is 
4.5.1 is 
4.5.2 is 
4.5.3 is
4.6.0 is
4.7.0 is
4.7.1 is
answered on Stack Overflow Jul 7, 2020 by Perry Qian-MSFT • edited Dec 4, 2020 by Perry Qian-MSFT

I assume that your are using .NET Framework. This error is known for ServiceStack.Redis and is tracked on GitHub. It occurs because you use libraries that depend on different versions of System.Runtime.CompilerServices.Unsafe. These transitive dependencies need to be resolved and consolidated to end up with one assembly in your output folder. You will end up with the latest of these versions. Consequently, if one of the libraries depends on a specific version that is older, it will not be found.

The bug that causes this issue is fixed in System.Runtime.CompilerServices.Unsafe 4.6.0. Use binding redirects, to load the specific version of the assembly that you need. Insert this snippet into all of your app.config files.

    <assemblyIdentity name="System.Runtime.CompilerServices.Unsafe" publicKeyToken="b03f5f7f11d50a3a" culture="neutral" />
    <bindingRedirect oldVersion="" newVersion="" />

You need to specify the assembly version of the assembly that you need as newVersion. This is not the same as the package version that you choose when installing your NuGet package. They correspond like this:

  • Package 4.5.3 contains assembly version is
  • Package 4.7.0 contains assembly version

In this binding redirect I use the newer version of System.Runtime.CompilerServices.Unsafe that fixes the bug. However, if you depend on the older version, use

answered on Stack Overflow Jul 7, 2020 by thatguy

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