Issues with swagger after migrating to .NET Core 3.0

Question

After migrating to .NET Core 3.0. I'm having issues configuring swagger.

Following is my configuration.

  public void ConfigureServices(IServiceCollection services)
  {       

       services.AddMvc().SetCompatibilityVersion(Microsoft.AspNetCore.Mvc.CompatibilityVersion.Version_3_0).AddNewtonsoftJson();


       services.AddSwaggerGen(setup =>
       {
             setup.SwaggerDoc(
                "v1", 
                 new Info 
                 {  
                     Title = "Docker", 
                     Version = "v1" 
                 });
        });
  }

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
       Configuration.SwaggerOptions swaggerOptions = new Configuration.SwaggerOptions();

       _configuration.GetSection("SwaggerOptions").Bind(swaggerOptions);

       app.UseSwagger(options =>
       {
            options.RouteTemplate = swaggerOptions.JsonRoot;
       });

       app.UseSwaggerUI(options =>
       {
           options.SwaggerEndpoint(swaggerOptions.UiEndpoint, swaggerOptions.ApiDescription);
       });
}

Following is the exception

TypeLoadException: Could not load type 'Microsoft.AspNetCore.Mvc.MvcJsonOptions' from assembly 'Microsoft.AspNetCore.Mvc.Formatters.Json

Is there a solution for this ?

Answer 1

There is a discussion on the aspnet/AspNetCore github repo discussing this: Restore MvcJsonOptions to ASP.NET Core 3.0 as a type forward?

It suggests the issue was resolved.

I'd suggest ensuring you have the latest Swashbuckle.AspnetCore package installed: https://www.nuget.org/packages/Swashbuckle.AspNetCore/

In the offical asp.net core docs, it states:

Install-Package Swashbuckle.AspNetCore -Version 5.0.0-rc2

https://docs.microsoft.com/en-us/aspnet/core/tutorials/getting-started-with-swashbuckle?view=aspnetcore-3.0&tabs=visual-studio

So I'd suggest you need to install a pre-release version, at the time of writing only 4.X is stable and 5.0.0-rc3 is the latest.