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Return empty json on null in WebAPI

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野性不改
野性不改 2021-02-04 02:50

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

4条回答
  • 甜味超标
    甜味超标 (楼主)
    2021-02-04 03:29

    Thanks to Darrel Miller, I for now use this solution.

    WebApi messes with StringContent "{}" again in some environment, so serialize through HttpContent.

    /// 
/// Sends HTTP content as JSON
/// 
/// Thanks to Darrel Miller
/// 
public class JsonContent : HttpContent
{
    private readonly JToken jToken;

    public JsonContent(String json) { jToken = JObject.Parse(json); }

    public JsonContent(JToken value)
    {
        jToken = value;
        Headers.ContentType = new MediaTypeHeaderValue("application/json");
    }

    protected override Task SerializeToStreamAsync(Stream stream, TransportContext context)
    {
        var jw = new JsonTextWriter(new StreamWriter(stream))
        {
            Formatting = Formatting.Indented
        };
        jToken.WriteTo(jw);
        jw.Flush();
        return Task.FromResult(null);
    }

    protected override bool TryComputeLength(out long length)
    {
        length = -1;
        return false;
    }
}



    Derived from OkResult to take advantage Ok() in ApiController
    


    public class OkJsonPatchResult : OkResult
{
    readonly MediaTypeWithQualityHeaderValue acceptJson = new MediaTypeWithQualityHeaderValue("application/json");

    public OkJsonPatchResult(HttpRequestMessage request) : base(request) { }
    public OkJsonPatchResult(ApiController controller) : base(controller) { }

    public override Task ExecuteAsync(CancellationToken cancellationToken)
    {
        var accept = Request.Headers.Accept;
        var jsonFormat = accept.Any(h => h.Equals(acceptJson));

        if (jsonFormat)
        {
            return Task.FromResult(ExecuteResult());
        }
        else
        {
            return base.ExecuteAsync(cancellationToken);
        }
    }

    public HttpResponseMessage ExecuteResult()
    {
        return new HttpResponseMessage(HttpStatusCode.OK)
        {
            Content = new JsonContent("{}"),
            RequestMessage = Request
        };
    }
}

    


    Override Ok() in ApiController
    


    public class BaseApiController : ApiController
{
    protected override OkResult Ok()
    {
        return new OkJsonPatchResult(this);
    }
}

    
    
    
             
    
                                                        
    
            
            
    
              
                
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