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

Answer 1

@OzBob's answer assumes you only want to add a single attribute to a method. If you want to add and document more than one content types for the same method, you can use the following:

SwaggerResponseContentTypeAttribute.cs

/// 

/// SwaggerResponseContentTypeAttribute
/// 
[AttributeUsage(AttributeTargets.Method, AllowMultiple = true)]
public class SwaggerResponseContentTypeAttribute : Attribute
{
    /// 

    /// SwaggerResponseContentTypeAttribute
    /// 
    /// 
    public SwaggerResponseContentTypeAttribute(string responseType)
    {
        ResponseType = responseType;
    }
    /// 

    /// Response Content Type
    /// 
    public string ResponseType { get; private set; }

    /// 

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

ResponseContentTypeOperationFilter.cs

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

        foreach (var requestAttribute in requestAttributes)
        {
            if (requestAttribute.Exclusive)
            {
                operation.produces.Clear();
            }
            operation.produces.Add(requestAttribute.ResponseType);
        }
    }
}

Note that when you have multiple attributes on the same method and you want to replace the existing content types, you should set Exclusive = true on the first attribute only. Otherwise, you won't get all the attributes into the documentation.