Azure Function, EF Core, Can't load ComponentModel.Annotations 4.2.0.0

I have created several .Net Standard 2.0 libraries, tested the execution via a console application, as well as several tests - all is good.

Move over to azure function, and get the following run-time error:

I then try to download that specific version into the API Function project:

I'm using Visual Studio Version 15.7.0 Preview 5.0. I have updated the Azure Function to 4.7... as the console and test projects are - and those work.

Been at this a far too many hours.. so I'm hoping the resolution isn't something crazy. Ef Core 2.1.0-rc1-final is also in the mix. Using data annotations for Required, MaxLength, NotMapped.

Error in graphic says: Microsoft.EntityFrameworkCore: Could not load file or assembly 'System.ComponentModel.Annotations, Version=4.2.0.0

Solution 1:

I would suggest running this function below once you start your Azure Function. It will redirect any assembly to an existing version.

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;
    }

}

Solution 2:

I followed the instructions here:

https://codopia.wordpress.com/2017/07/21/how-to-fix-the-assembly-binding-redirect-problem-in-azure-functions/

And added the following redirect:

"BindingRedirects": "[ { "ShortName": "System.ComponentModel.Annotations", "RedirectToVersion": "4.2.1.0", "PublicKeyToken": "b03f5f7f11d50a3a" } ]"

NOTE: Its not v 4.5.0.0 ... Its actually 4.2.1.0.

Solution 3:

The accepted response will cause a CPU leak due to the += if it is misused, and will grind your function app to a halt. If you are using IoC, it is better to use a singleton. Here:

public class FunctionsAssemblyResolver
{
    static FunctionsAssemblyResolver()
    {
        AppDomain.CurrentDomain.AssemblyResolve += CurrentDomain_AssemblyResolve;
    }

    // At least one static member needs to be invoked in order to execute the static constructor,
    // but it will only run the constructor once.
    public static void StaticInstance() { }

    private static Assembly CurrentDomain_AssemblyResolve(object sender, ResolveEventArgs args)
    {
        var requestedAssembly = new AssemblyName(args.Name);
        try
        {
            // Feel free to resolve any other assemblies, but this will take care of Annotations
            return requestedAssembly.Name == "System.ComponentModel.Annotations"
                ? Assembly.Load(requestedAssembly.Name)
                : null;
        }
        catch
        {
            // do nothing
        }

        return null;
    }
}

To use, just call FunctionsAssemblyResolver.StaticInstance() prior to any IoC resolves. This can also be used for any non-IoC approach as well.

Solution 4:

Add the latest ComponentModel reference into your project using nuget command from Package Manager Console will solve this issue for all type application (Console/Web/Azure).

Install-Package System.ComponentModel.Annotations -Version 4.5.0

Since ComponentModel has not a release of 4.2.0.0 that's why try to install the latest on. Reference: -

Neget Gallery