Azure AD b2c error – could not load file or assembly ‘microsoft.identitymodel.protocol.extensions’

Following the Azure B2C Dev Quickstarts resulted in a build failure…

Could not load file or assembly ‘Microsoft.IdentityModel.Protocol.Extensions’ or one of its dependencies. The located assembly’s manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)

The quick fix is to update the Nuget package reference for the Protocol Extensions from version 1.0.0.0 to 1.0.2.33 using the Visual Studio Nuget package manager.

Subsequently the build then fails with this error;

The following errors occurred while attempting to load the app.
– No assembly found containing an OwinStartupAttribute.
– No assembly found containing a Startup or [AssemblyName].Startup class.
To disable OWIN startup discovery, add the appSetting owin:AutomaticAppStartup with a value of “false” in your web.config.
To specify the OWIN startup Assembly, Class, or Method, add the appSetting owin:AppStartup with the fully qualified startup class or configuration method name in your web.config.

The fix for this one is to check your Startup.cs file for the OWIN assembly declaration.

using Microsoft.Owin;
using Owin;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

[assembly: OwinStartup(typeof(WebApp_OpenIDConnect_DotNet_B2C.Startup))]

namespace WebApp_OpenIDConnect_DotNet_B2C
{
  public partial class Startup
  {
    public void Configuration(IAppBuilder app)
    {
      ConfigureAuth(app);
    }
  }
}

These few changes should then result in a successful build.