What is causing the error that swagger is already in the route collection for Web API 2?

Question

I installed Swagger in my ASP.Net MVC Core project and it is documenting my API beautifully.

My co-worker asked me to install it in a full framework 4.6.1 project so I've done the following.

In Package Console Manager run:

Install-Package Swashbuckle

To get your Test Web API controller working: 1) Comment this out in the WebApi.config:

// config.SuppressDefaultHostAuthentication();
// config.Filters.Add(new HostAuthenticationFilter(OAuthDefaults.AuthenticationType));

Now this URL: http://localhost:33515/api/Test brings back XML:

<ArrayOfstring xmlns:i="http://www.w3.org/2001/XMLSchema-instance"     xmlns="http://schemas.microsoft.com/2003/10/Serialization/Arrays">
<string>value1</string>
<string>value2</string>
</ArrayOfstring>

In Global.asax Register() I call:

 SwaggerConfig.Register();

In AppStart.Swagger.Config Register() I put:

public class SwaggerConfig
{
    public static void Register()
    {     
       var thisAssembly = typeof(SwaggerConfig).Assembly;
       GlobalConfiguration.Configuration
            .EnableSwagger(c =>
                {
                    c.SingleApiVersion("v1.0", "HRSA CHAFS");
                    c.IncludeXmlComments(GetXmlCommentsPath());
                })
              .EnableSwaggerUi(c =>
                {});
    }

    private static string GetXmlCommentsPath()
    {
        var path = String.Format(@"{0}bin\Services.XML", AppDomain.CurrentDomain.BaseDirectory);
        return path;

    }
}

Now I get this error: "A route named 'swagger_docsswagger/docs/{apiVersion}' is already in the route collection. Route names must be unique."

I've been stuck on this for hours. How do you get rid of this?

Answer 1

This can happen when you re-name your .NET assembly. A DLL with the previous assembly name will be present in your bin folder. This causes the swagger error.

Delete your bin folder and re-build your solution. This resolves the swagger error.

Answer 2

Swagger config uses pre-application start hook, so you don't need to call SwaggerConfig.Register() explicitly. Otherwise Register method is called twice.

[assembly: PreApplicationStartMethod(typeof(SwaggerConfig), "Register")]