Return empty json on null in WebAPI

Question

Is it possible to return { } instead of null when webApi returns a null object? This, to prevent my user from getting errors while parsing the response. And to make the respon

Answer 1

You can use a HttpMessageHandler to perform behaviour on all requests. The example below is one way to do it. Be warned though, I whipped this up very quickly and it probably has a bunch of edge case bugs, but it should give you the idea of how it can be done.

  public class NullJsonHandler : DelegatingHandler
    {
        protected override async Task SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
        {

            var response = await base.SendAsync(request, cancellationToken);
            if (response.Content == null)
            {
                response.Content = new StringContent("{}");
            } else if (response.Content is ObjectContent)
            {
                var objectContent = (ObjectContent) response.Content;
                if (objectContent.Value == null)
                {
                    response.Content = new StringContent("{}");
                }

            }
            return response;
        }
    }

You can enable this handler by doing,

config.MessageHandlers.Add(new NullJsonHandler());