asp.net web api2 - Swashbuckle Swagger - How to annotate content types?

Question

How do I annotate my ASP.NET WebAPI actions so that the swagger metadata includes the content-types that my resources support?

Specifically, I want the documentation to show that one of my resources can return the 'original' application/json and application/xml but also now returns a new format, application/vnd.blah+json or +xml.

Answer 1

Extending @VisualBean's answer.

On a Controller's API method, you could use the code below to set an Attribute like:

[SwaggerResponseContentType(responseType:"application/pdf", Exclusive=true)]
public HttpResponseMessage GetAuthorityForm(string id)
{
....

Note: 'Exclusive=true' will remove all other content types, otherwise using the new Attribute will add a new Response Content Type in the Swagger UI drop down. It will NOT modify your Controller or API, just the documentation.

SwaggerConfig.cs

 GlobalConfiguration.Configuration
            .EnableSwagger(c =>
 // Set filter to apply Custom Content Types to operations
 //
 c.OperationFilter<ResponseContentTypeOperationFilter>();

SwaggerResponseContentTypeAttribute.cs

/// <summary>
/// SwaggerResponseContentTypeAttribute
/// </summary>
[AttributeUsage(AttributeTargets.Method)]
public sealed class SwaggerResponseContentTypeAttribute : Attribute
{
    /// <summary>
    /// SwaggerResponseContentTypeAttribute
    /// </summary>
    /// <param name="responseType"></param>
    public SwaggerResponseContentTypeAttribute(string responseType)
    {
        ResponseType = responseType;
    }
    /// <summary>
    /// Response Content Type
    /// </summary>
    public string ResponseType { get; private set; }

    /// <summary>
    /// Remove all other Response Content Types
    /// </summary>
    public bool Exclusive { get; set; }
}

ResponseContentTypeOperationFilter.cs

public class ResponseContentTypeOperationFilter : IOperationFilter
{
    public void Apply(Operation operation, SchemaRegistry schemaRegistry, ApiDescription apiDescription)
    {
        var requestAttributes = apiDescription.GetControllerAndActionAttributes<SwaggerResponseContentTypeAttribute>().FirstOrDefault();

        if (requestAttributes != null)
        {
            if (requestAttributes.Exclusive)
                operation.produces.Clear();

            operation.produces.Add(requestAttributes.ResponseType);
        }
    }
}