Question

I am facing a weird issues while fetching base64 encoded string sent from client to WCF Service at server. This string is always coming null in my WCF service method. The Business class I am having is:

[DataContract(Namespace = "")]
public class Test
{
    [DataMember]
    public int Id { get; set; }
    [DataMember]
    public int Name { get; set; }
    [DataMember]
    public int Age { get; set; }
    [DataMember]
    public string MyString { get; set; }
}

I am sending the post data in xml for to my WCF service:

    string data = string.Format("<Test><Id>{0}</Id><Name>{1}</Name><Age>{2}</Age><MyString>{3}</MyString></Test>",
        1, "name", 20, Convert.ToBase64String(image));//image is in bytes

Above “image” is in bytes.

While receiving the client data at server in MyTestService.svc.cs:

  public void CreateTest(Test test)
    {

in the “test” object I am getting the values of all properties which I sent from client except “MyString” property. It is always coming null. I double checked in Fiddler the “MyString” tag in xml contains the base64 encoded string. Can you help me fixing this?

Is there any limit for length of property value in xml tag. The encoded string of image is long enough.

Answer 1

The DataContractSerializer (the default serializer for WCF) enforces the order of the elements in a data contract. If you don’t specify an order explicitly using the Order property of the [DataMember] attribute, the default order is alphabetical. Try sending the request in that order (Age, Id, MyString, Name), and you should see the value of MyString correctly populated.

public class StackOverflow_12693581
{
    [DataContract(Namespace = "", Name = "Test")]
    public class TestData
    {
        [DataMember]
        public int Id { get; set; }
        [DataMember]
        public string Name { get; set; }
        [DataMember]
        public int Age { get; set; }
        [DataMember]
        public string MyString { get; set; }
    }
    [ServiceContract]
    public interface ITest
    {
        [OperationContract]
        void Process(TestData test);
    }
    public class Service : ITest
    {
        public void Process(TestData test)
        {
            Console.WriteLine("MyString: {0}", test.MyString ?? "<<NULL>>");
        }
    }
    public static void Test()
    {
        string baseAddress = "http://" + Environment.MachineName + ":8000/Service";
        WebServiceHost host = new WebServiceHost(typeof(Service), new Uri(baseAddress));
        host.Open();
        Console.WriteLine("Host opened");

        byte[] image = Enumerable.Range(1, 100).Select(i => (byte)i).ToArray();

        WebClient c = new WebClient();
        Console.WriteLine("Order as in the question");
        string data = string.Format("<Test><Id>{0}</Id><Name>{1}</Name><Age>{2}</Age><MyString>{3}</MyString></Test>",
            1, "name", 20, Convert.ToBase64String(image));//image is in bytes 
        c.Headers[HttpRequestHeader.ContentType] = "text/xml";
        c.UploadString(baseAddress + "/Process", data);
        Console.WriteLine();

        c = new WebClient();
        Console.WriteLine("Correct order");
        data = string.Format("<Test><Age>{2}</Age><Id>{0}</Id><MyString>{3}</MyString><Name>{1}</Name></Test>",
            1, "name", 20, Convert.ToBase64String(image));//image is in bytes 
        c.Headers[HttpRequestHeader.ContentType] = "text/xml";
        c.UploadString(baseAddress + "/Process", data);

        Console.Write("Press ENTER to close the host");
        Console.ReadLine();
        host.Close();
    }
}