Azure Function Could not load file or assembly 'System.Security.Cryptography.Pkcs'

Question

I recently tried decrypting and verifying PKCS#7 message in C# .NET Core 3.1 Web Application. Here is how I did it.

I used System.Security.Cryptography.Pkcs in Web app project. But after implementing same package and trying to decrypt and verify in Azure function, it returns exception

{"Could not load file or assembly 'System.Security.Cryptography.Pkcs, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'. The system cannot find the file specified.":"System.Security.Cryptography.Pkcs, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a"}.

I tried several stack overflow answers but couldn't sort it.

System.Security.Cryptography.X509Certificates is working fine in Azure function, but Pkcs seems to have issue.

Anyway I can sort it out?

Here is my .csproj:

<Project Sdk="Microsoft.NET.Sdk">
<PropertyGroup>
<TargetFramework>netcoreapp3.1</TargetFramework>
<AzureFunctionsVersion>v3</AzureFunctionsVersion>
<UserSecretsId>695a883e-9b1a-4d55-98a9-0b47b683bbb2</UserSecretsId>
<Nullable>annotations</Nullable>
</PropertyGroup>
<ItemGroup>
    <PackageReference Include="Autofac" Version="6.1.0" />
    <PackageReference Include="Dapper" Version="2.0.78" />
    <PackageReference Include="Microsoft.ApplicationInsights.WorkerService" Version="2.15.0" />
    <PackageReference Include="Microsoft.Azure.Functions.Extensions" Version="1.1.0" />
    <PackageReference Include="Microsoft.Azure.WebJobs.Extensions.DurableTask" Version="2.4.2" />
    <PackageReference Include="Microsoft.NET.Sdk.Functions" Version="3.0.11" />
    <PackageReference Include="System.Collections" Version="4.3.0" />
    <PackageReference Include="System.Data.SqlClient" Version="4.8.2" />
    <PackageReference Include="System.Security.Cryptography.Pkcs" Version="6.0.0" />
</ItemGroup>
<ItemGroup>
<None Update="host.json">
  <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
</None>
<None Update="local.settings.json">
  <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
  <CopyToPublishDirectory>Never</CopyToPublishDirectory>
</None>
</ItemGroup>
</Project>

Answer 1

Mishra](https://stackoverflow.com/users/13378259/rocky-mishra) Glad that your issue got resolved and posting your suggestion as answer to help the other community members who face similar kind of issue.

Below example code with helping in resolving the issue.

public class FunctionsAssemblyResolver
{
    public static void RedirectAssembly()
    {
        var list = AppDomain.CurrentDomain.GetAssemblies().OrderByDescending(a => a.FullName).Select(a => a.FullName).ToList();
        AppDomain.CurrentDomain.AssemblyResolve += CurrentDomain_AssemblyResolve;
    }

    private static Assembly CurrentDomain_AssemblyResolve(object sender, ResolveEventArgs args)
    {
        var requestedAssembly = new AssemblyName(args.Name);
        Assembly assembly = null;
        AppDomain.CurrentDomain.AssemblyResolve -= CurrentDomain_AssemblyResolve;
        try
        {
            assembly = Assembly.Load(requestedAssembly.Name);
        }
        catch (Exception ex)
        {
        }
        AppDomain.CurrentDomain.AssemblyResolve += CurrentDomain_AssemblyResolve;
        return assembly;
    }

}

For further information check this SO.