Response body is not returning from custom error responses in swagger Swashbuckle

Question

I have integrated swagger to a dot.net core API application using Swashbuckle. When I execute an API via Swagger UI without providing credentials it is returning a "401- Unauthorized" response as expected.

But it is not showing the error response which I have configured to return as a custom error response as the body. It does returns the header as below image.

When I execute the same API via Postman it does return the custom error response as below.

What I need is, I need to see the custom error response body in the swagger UI as well.

In Postman,

In Swagger,

Same scenario with the 403 and 404 status codes.

Answer 1

After struggling a lot I have found the root cause to the issue.It is due to not having configure the Response Content type in the "app.UseStatusCodePages" middle ware.

  // Custom status handling
        app.UseStatusCodePages(async (StatusCodeContext context) =>
        {
            var settings = new JsonSerializerSettings();
            settings.NullValueHandling = NullValueHandling.Ignore;
            settings.Formatting = Formatting.Indented;

            int statusCode = context.HttpContext.Response.StatusCode;
            ***context.HttpContext.Response.ContentType = "application/json";*** // Added this line to solve the issue

            await context.HttpContext.Response.WriteAsync(JsonConvert.SerializeObject(
                new ErrorResponse((HttpStatusCode)statusCode,
                ReasonPhrases.GetReasonPhrase(statusCode)
                ), settings));
        });

Had to add "context.HttpContext.Response.ContentType = "application/json";" to fix the issue.