Xamarin将图像上传到REST Web服务器（错误请求）

Question

I know that this question has already been posted more than one time but I'm still hanged with the problem of sending one image from a Xamarin client to a REST web server. I receive a BadRequest error on the client side but I don't know if it comes from the server or from the client.

Here is the Xamarin code (client side) :

public class WsDest
{
   public string D_ID { get; set; }
   public string D_NOM { get; set; }
   public string D_CAT1 { get; set; }
   public string D_CAT2 { get; set; }
   public string D_ANNEE { get; set; }
   public Byte[] D_PHOTO1 { get; set; }
}

static async Task<string> Do_UpdateVehiculeInfos(WsDest Dest)
{
    string cRet = "";
    string cIP = Application.Current.Properties["IPSERVEUR"].ToString().Trim();


    using (HttpClient client = new HttpClient())
    {
        try
        {
            var oJson = JsonConvert.SerializeObject(Dest);
            var cJson = new StringContent(oJson, Encoding.UTF8, "application/json");

            client.DefaultRequestHeaders.Accept.Add(new System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("Application/json"));
            client.Timeout = TimeSpan.FromMilliseconds(8000);
            client.MaxResponseContentBufferSize = 3000000;
            client.BaseAddress = new Uri(cIP + "/MyWebService.svc/");
            using (HttpResponseMessage r = await client.PostAsync("UpdateVehicule", cJson))
            {
                if (r.IsSuccessStatusCode)
                {
                    await Application.Current.MainPage.DisplayAlert("", "Mise à jour effectuée !", "+OK+");
                    await Application.Current.MainPage.Navigation.PopAsync(); //Remove the page currently on top (= retourne à la page d'avant)
                }
                else
                {
                    await Application.Current.MainPage.DisplayAlert("", r.ReasonPhrase.ToString(), "-OK-");
                }

            }
        }
        catch (Exception e)
        {
            await Application.Current.MainPage.DisplayAlert("", e.Message, "/OK/");
        }
    }
    return cRet;
}

On the server side :

[DataContract]
public class WsDest
{
    [DataMember]
    public string D_ID { get; set; }
    [DataMember]
    public string D_NOM { get; set; }
    [DataMember]
    public string D_CAT1 { get; set; }
    [DataMember]
    public string D_CAT2 { get; set; }
    [DataMember]
    public string D_ANNEE { get; set; }
    [DataMember]
    public Byte[] D_PHOTO1 { get; set; }
}

[OperationContract]
[WebInvoke(Method = "POST", RequestFormat = WebMessageFormat.Json, ResponseFormat = WebMessageFormat.Json, UriTemplate = "UpdateVehicule")]
bool UpdateVehicule(WsDest DestUpdate) ;



public bool UpdateVehicule(WsDest DestRecep)
{
    // my code to process data and image
}

The BadRequest message desapears when I set Dest.D_PHOTO1 to null on client side.

Does anybody have an idea on this subject?

Answer 1

Can you show us how the JSON looks like with the byte having a value?<<

Before the Json.SerializeObject(Dest), DEST.D_PHOTOS1 is {byte[6855981]}. [137,80,70,....] After the serialization, it's something more 'exotic' :

Before and after serialization

Eric