Could not load file or assembly 'System.Threading.Tasks.Extensions, Version=4.2.0.0

Question

I recently installed CsvHelper (https://joshclose.github.io/CsvHelper/) when i try to use the library I get the following error:

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 located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)

In my app.config I have binding redirect:

 <dependentAssembly>
            <assemblyIdentity name="System.Threading.Tasks.Extensions" publicKeyToken="cc7b13ffcd2ddd51" culture="neutral" />
            <bindingRedirect oldVersion="0.0.0.0-4.2.0.1" newVersion="4.2.0.1" />
        </dependentAssembly>

Also in my project I have reference to

\packages\System.Threading.Tasks.Extensions.4.5.3\lib\netstandard2.0\System.Threading.Tasks.Extensions.dll

Its version is 4.2.0.1 I am not sure why its still trying to load 4.2.0.0 of the library.

my project is running .net 4.7.2

Answer 1

So i created a new .NET 472 project then added all the libs etc and code and now it works.

I suspect it originally broke because I had installed a really old version of csvhelper lib with excel plugin. Even though i removed it and removed all references it was still picking it up from somewhere.

Answer 2

According to https://github.com/JoshClose/CsvHelper/issues/1462 this seems to be a bug in one of the CSVHelper 15.0.0 dependencies. The 15.0.0 version (not sure about earlier ones) brings in some other assembly which causes the problem.

Personally I worked around this by downgrading to 13.0 (a comment also noted that 12.3.2 worked), but that bug report now states that they have released 15.0.1 specifically to fix this. I've yet to confirm that myself.

Answer 3

I had the same problem today in a multi project solution, System.Threading.Tasks.Extensions got installed by embedding the Autofac package. After removing and reinstalling Autofac (via nuget) in both projects, the two packages.config contained the same entry

<package id="System.Threading.Tasks.Extensions" version="4.5.4" targetFramework="net472" />

but while one project referenced the correct dll in

packages\System.Threading.Tasks.Extensions.4.5.4\lib

the other one referenced the older version in

packages\System.Threading.Tasks.Extensions.4.5.2\lib

After manually removing the older dll from the references (not via nuget) and embedding the correct one, everything worked again. I don't see why the correct packages.config entry did not enforce the correct reference.

EDIT:

If it works on your dev machine but not on the machine you deployed to, don't forget to deploy the binding redirects in web.config / app.config. In my case they look like so:

<dependentAssembly>
  <assemblyIdentity name="System.Threading.Tasks.Extensions" publicKeyToken="cc7b13ffcd2ddd51" culture="neutral" />
  <bindingRedirect oldVersion="0.0.0.0-4.2.0.1" newVersion="4.2.0.1" />
</dependentAssembly>

Answer 4

I had this problem today in a multi-project solution. Fixed it by updating other NuGet packages in the offending project. Unfortunately, not sure which one fixed the problem.

Current version of CsvHelper: 15.0.5.

Answer 5

<assemblyBinding>
  <probing privatePath="System.Threading.Tasks.Extensions.dll"/>
</assemblyBinding>
            <assemblyBinding>
  <probing privatePath="System.Runtime.CompilerServices.Unsafe.dll"/>
</assemblyBinding>
    <assemblyBinding>
  <probing privatePath="Microsoft.Bcl.AsyncInterfaces.dll"/>
</assemblyBinding>

Answer 6

I had this problem in a multi-project solution when upgrading .net version. In my case running Update-Package -reinstall command in Package Manager Console solved the problem.

Answer 7

This answer assumes that you are using PackageReference for your nuget references. If that's the case, there is also a known bug in PackageReference .Net tooling model. For some weird cases, the nuget restore msbuild tool chain places ref assemblies, when it should have ideally placed the lib assemblies. How can you find out if you are facing a similar problem? You can use a standard reflector application like ILSpy to read the failing library's metadata in your working directory. If you see RefAssemblies attribute in its metadata, then you are also encountering this problem.

To fix this problem, you can use something like the following tag in your csproj file to fix the nuget copying issue.

<Target Name="ReplaceRefWithLib" BeforeTargets="ResolveAssemblyReferences">
    <ItemGroup>
        <_noCopyRefs Include="@(Reference)" Condition="'%(Reference.Private)' == 'false'" />
        <_noCopyRefsByFileName Include="@(_noCopyRefs->'%(FileName)')">
            <OriginalItem>%(Identity)</OriginalItem>
        </_noCopyRefsByFileName>
        <_libByFileName Include="@(ReferenceCopyLocalPaths->'%(FileName)')">
            <OriginalItem>%(Identity)</OriginalItem>
        </_libByFileName>
        <_overlappingRefByFileName Include="@(_noCopyRefsByFileName)" Condition="'@(_noCopyRefsByFileName)' == '@(_libByFileName)' AND '%(Identity)' != ''" />
        <_overlappingLibByFileName Include="@(_libByFileName)" Condition="'@(_noCopyRefsByFileName)' == '@(_libByFileName)' AND '%(Identity)' != ''" />
        <_overlappingRef Include="@(_overlappingRefByFileName->'%(OriginalItem)')" />
        <_overlappingLib Include="@(_overlappingLibByFileName->'%(OriginalItem)')" />
    </ItemGroup>
    <ItemGroup Condition="'@(_overlappingRef)' != ''">
        <Reference Remove="@(_overlappingRef)" />
        <Reference Include="@(_overlappingLib)">
        <Private>false</Private>
        </Reference>
    </ItemGroup>
</Target>

Hoping this helps.

Answer 8

In my case I had a different version of System.Threading.Tasks.Extensions in my unit testing project than in my main project so after I upgraded my unit testing project to match the version it worked for me.

Answer 9

I go this error when running a console app (.NEt framework 4.7.2) consuming a "native" class library, which in turn consumed the System.Threading.Tasks.Extensions dll. Removing the class library from the console application and then re-adding it again, solved the issue.

Answer 10

I had similar issue for couple of dlls which added newly in C# project references where I was using .exe.config file to do binding redirect. I have mentioned old and new version in .exe.config file but it was giving same error. I used this link to enable binding redirect logs: How to enable assembly bind failure logging (Fusion) in .NET I found out that sometime dll getting loaded from wrong folder(as at multiple location same dll with different version are available) or wrong binding version given in .exe.config

example: Folder path where .exe.config placed : C:\folder1

Folder path where System.Threading.Tasks.Extensions.dll placed : C:\folder1\abc\xyz