Exc.: Could not load file or assembly 'Newtonsoft.Json, Version=6.0.0.0, Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed' or one of its dependencies

Question

I am using the Microsoft.AspNet.WebApi.Client (Version 5.2.4). Also Newtonsoft.Json is referenced in my project (Version 11.0.2).

I am trying to get the results of a web-service call as follows:

...

using (var client = new HttpClient())
{
      ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;

      client.DefaultRequestHeaders.Accept.Clear();
      client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

      var content = new StringContent($"grant_type=refresh_token&client_id=sfd34tgregge&client_secret=345534535&refresh_token={refreshToken}", Encoding.UTF8, "application/x-www-form-urlencoded");

      var response = await client.PostAsync(url, content);

      if (response.IsSuccessStatusCode)
      {
        var getAccessTokenResult = await response.Content.ReadAsAsync<GetAccessTokenResult>();

            ...
      }
 }

 ...

I can execute this code without any problems when I reference this DLL from a C# application.

When I call the same method via COM I get the following error:

Exception: Could not load file or assembly 'Newtonsoft.Json, Version=6.0.0.0, Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed' or one of its dependencies. The system could not find the specified file.

We decorated the class that is accessible via COM in the following way:

[ProgId("MyDll")]
[ClassInterface(ClassInterfaceType.AutoDual)]
public class MyDll : IMyDll
{
    ...
}

We have also set the following in AssemblyInfo.cs:

[assembly: ComVisible(true)]

app.config contains the following:

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <runtime>
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
      <dependentAssembly>
        <assemblyIdentity name="Newtonsoft.Json" publicKeyToken="30ad4fe6b2a6aeed" culture="neutral"/>
        <bindingRedirect oldVersion="0.0.0.0-11.0.0.0" newVersion="11.0.0.0"/>
      </dependentAssembly>
    </assemblyBinding>
  </runtime>
<startup><supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5.2"/></startup></configuration>

Why do I get this error message? Why does this try to use Version 6.0.0.0 of Newtonsoft.Json? Why does this work when calling it from a .NET application but not when calling it via COM? What else can I check?

Answer 1

Does the application that references it has the same version of Newtonsoft.json AND same /compatible version of .NET ?

It's worth checking your packages.config file and your packages folder.