[WebGet( UriTemplate = "/gast/{customer_id}/{year}/{gast_id}", ResponseFormat = WebMessageFormat.Json )]
[OperationContract]
public acsEintrittGast GetGastInfo( string customer_id, string year, string gast_id ) {
    acsEintrittGast gast = new acsEintrittGast();
    gast.ID = Guid.Parse( gast_id );
    gast.Bitmap = File.ReadAllBytes( dataPath + customer_id + "\" + year + "\" + gast_id + ".jpg" );
    return gast;
}

[WebInvoke( UriTemplate = "/gast/{customer_id}/{year}",
    ResponseFormat = WebMessageFormat.Json,
    RequestFormat = WebMessageFormat.Json,
    BodyStyle = WebMessageBodyStyle.Wrapped,
    Method = "POST" )]

[OperationContract]
public acsEintrittGast SetGastInfo( string customer_id, string year, acsEintrittGast GastObject /*string GastString*/ ) {
    acsEintrittGast Gast = null;
    try {
        //Gast = JsonConvert.DeserializeObject<acsEintrittGast>( (string)GastObject);
        File.WriteAllBytes( dataPath + customer_id + "\" + year + "\" + Gast.ID.ToString() + ".jpg", Gast.Bitmap.ToArray<byte>() );
    }
    catch {
    }
    return Gast;
}

public async static Task<T> SetRESTData( string URI, T Content ) {
    T res = default( T );

    HttpClient httpClient = null;
    HttpResponseMessage response = null;
    StreamReader sr  = null;
    StreamWriter writer = null;
    MemoryStream ms = null;
    try {
        httpClient = new HttpClient();

        string s = JsonConvert.SerializeObject( Content );
        StringContent theContent = new StringContent( s, System.Text.Encoding.UTF8, "application/json" );

        using( HttpRequestMessage request = new HttpRequestMessage( HttpMethod.Post, BaseURI + URI ) ) {
            request.Content = theContent;
            response = await httpClient.SendAsync( request );
        }
    }
    catch {
    }
    finally {
        if( sr != null ) {
            sr.Close();
            sr = null;
        }
        if( writer != null ) {
            writer.Close();
            writer = null;
        }
        if( ms != null ) {
            ms.Dispose();
            ms = null;
        }
        if( response != null ) {
            response.Dispose();
            response = null;
        }
        if( httpClient != null ) {
            httpClient.Dispose();
            httpClient = null;
        }
    }
    return res;
}

[DataContract( Name = "acsEintrittGast", Namespace = "" )]
public class acsEintrittGast {
    private Guid id = Guid.NewGuid();
    [DataMember( Name = "id", Order = 1 )]
    public Guid ID {
        get { return id; }
        set { id = value; }
    }

    private Byte[] bitmap = null;
    [DataMember( Name = "bitmap", Order = 1 )]
    public Byte[] Bitmap {
        get { return bitmap; }
        set { bitmap = value; }
    }

    private DateTime lastEntry = new DateTime( 1900, 1, 1 );
    [DataMember( Name = "lastEntry", Order = 1 )]
    public DateTime LastEntry {
        get { return lastEntry; }
        set { lastEntry = value; }
    }
}

acsEintrittGast gast = new acsEintrittGast();
gast.Bitmap = new byte[80455];
gast.ID = Guid.NewGuid();
await acsService.SetGastImfo( ftpLicID, currentYear, gast );