How do I serialize an enum value as an int?

Question

I want to serialize my enum-value as an int, but i only get the name.

Here is my (sample) class and enum:

public class Request {
    public RequestType request;
}

public enum RequestType
{
    Booking = 1,
    Confirmation = 2,
    PreBooking = 4,
    PreBookingConfirmation = 5,
    BookingStatus = 6
}

And the code (just to be sure i'm not doing it wrong)

Request req = new Request();
req.request = RequestType.Confirmation;
XmlSerializer xml = new XmlSerializer(req.GetType());
StringWriter writer = new StringWriter();
xml.Serialize(writer, req);
textBox1.Text = writer.ToString();

This answer (to another question) seems to indicate that enums should serialize to ints as default, but it doesn't seem to do that. Here is my output:

<?xml version="1.0" encoding="utf-16"?>
<Request xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <request>Confirmation</request>
</Request>

I have been able to serialize as the value by putting an "[XmlEnum("X")]" attribute on every value, but this just seems wrong.

Answer 1

The easiest way is to use [XmlEnum] attribute like so:

[Serializable]
public enum EnumToSerialize
{
    [XmlEnum("1")]
    One = 1,
    [XmlEnum("2")]
    Two = 2
}

This will serialize into XML (say that the parent class is CustomClass) like so:

<CustomClass>
  <EnumValue>2</EnumValue>
</CustomClass>

Answer 2

Most of the time, people want names, not ints. You could add a shim property for the purpose?

[XmlIgnore]
public MyEnum Foo {get;set;}

[XmlElement("Foo")]
[EditorBrowsable(EditorBrowsableState.Never), Browsable(false)]
public int FooInt32 {
    get {return (int)Foo;}
    set {Foo = (MyEnum)value;}
}

Or you could use IXmlSerializable, but that is lots of work.

Answer 3

Take a look at the System.Enum class. The Parse method converts a string or int representation into the Enum object and the ToString method converts the Enum object to a string which can be serialized.

Answer 4

using System.Xml.Serialization;

public class Request
{    
    [XmlIgnore()]
    public RequestType request;

    public int RequestTypeValue
    {
      get 
      {
        return (int)request;
      } 
      set
      {
        request=(RequestType)value; 
      }
    }
}

public enum RequestType
{
    Booking = 1,
    Confirmation = 2,
    PreBooking = 4,
    PreBookingConfirmation = 5,
    BookingStatus = 6
}

The above approach worked for me.

Answer 5

Please see the full example Console Application program below for an interesting way to achieve what you're looking for using the DataContractSerializer:

using System;
using System.IO;
using System.Runtime.Serialization;

namespace ConsoleApplication1
{
    [DataContract(Namespace="petermcg.wordpress.com")]
    public class Request
    {
        [DataMember(EmitDefaultValue = false)]
        public RequestType request;
    }

    [DataContract(Namespace = "petermcg.wordpress.com")]
    public enum RequestType
    {
        [EnumMember(Value = "1")]
        Booking = 1,
        [EnumMember(Value = "2")]
        Confirmation = 2,
        [EnumMember(Value = "4")]
        PreBooking = 4,
        [EnumMember(Value = "5")]
        PreBookingConfirmation = 5,
        [EnumMember(Value = "6")]
        BookingStatus = 6
    }

    class Program
    {
        static void Main(string[] args)
        {
            DataContractSerializer serializer = new DataContractSerializer(typeof(Request));

            // Create Request object
            Request req = new Request();
            req.request = RequestType.Confirmation;

            // Serialize to File
            using (FileStream fileStream = new FileStream("request.txt", FileMode.Create))
            {
                serializer.WriteObject(fileStream, req);
            }

            // Reset for testing
            req = null;

            // Deserialize from File
            using (FileStream fileStream = new FileStream("request.txt", FileMode.Open))
            {
                req = serializer.ReadObject(fileStream) as Request;
            }

            // Writes True
            Console.WriteLine(req.request == RequestType.Confirmation);
        }
    }
}

The contents of request.txt are as follows after the call to WriteObject:

<Request xmlns="petermcg.wordpress.com" xmlns:i="http://www.w3.org/2001/XMLSchema-instance">
    <request>2</request>
</Request>

You'll need a reference to the System.Runtime.Serialization.dll assembly for DataContractSerializer.

Answer 6

Since you are assigning explicit non-sequential values to the enum options I am assuming you want to be able to specify more than one value at a time (binary flags), then the accepted answer is your only option. Passing in PreBooking | PreBookingConfirmation will have an integer value of 9 and the serializer will not be able to deserialize it, casting it with a shim property however will work well. Or maybe you just missed the 3 value :)

Answer 7

For me these solutions were not that satisfying. I like general solutions where i don't have to adjust them, when adjusting the enum values. So i created the following solution, using the XmlAttributeOverrides.

    public static XmlAttributeOverrides ReflectionAddXmlEnumAttributes(Type baseType, XmlAttributeOverrides overrides = null)
    {
        if (overrides == null) overrides = new XmlAttributeOverrides();
        // traversing all serializable members
        var filteredFields = baseType.GetFields()
            .Where(f =>
                (f.Attributes.HasFlag(FieldAttributes.Public) &&
                 !f.Attributes.HasFlag(FieldAttributes.Static) &&
                 !f.CustomAttributes.Any(
                     a => a.AttributeType.IsAssignableFrom(typeof(XmlIgnoreAttribute)))));
        var filteredProperties = baseType.GetProperties()
            .Where(f =>
                (f.GetMethod?.Attributes.HasFlag(MethodAttributes.Public) ?? false) &&
                !f.GetMethod.Attributes.HasFlag(MethodAttributes.Static) &&
                (f.SetMethod?.Attributes.HasFlag(MethodAttributes.Public) ?? false) &&
                !f.SetMethod.Attributes.HasFlag(MethodAttributes.Static) &&
                !f.CustomAttributes.Any(
                    a => a.AttributeType.IsAssignableFrom(typeof(XmlIgnoreAttribute))));

        var classMemberTypes = filteredFields.Select(f => f.FieldType)
            .Concat(filteredProperties.Select(p => p.PropertyType));

        foreach (var memberType in classMemberTypes)
        {
            // proceed the same way for sub members
            ReflectionAddXmlEnumAttributes(memberType, overrides);
            if (!memberType.IsEnum) continue;
            var enumFields = memberType.GetFields();
            foreach (var enumFieldInfo in enumFields)
            {
                if (!enumFieldInfo.IsLiteral) continue;
                // add attribute-overrides for every enum-literal
                var name = enumFieldInfo.Name;
                if (overrides[memberType, name] != null) continue;
                var integer = enumFieldInfo.GetRawConstantValue();
                var attribute = new XmlAttributes
                {
                    XmlEnum = new XmlEnumAttribute(integer.ToString()),
                };
                overrides.Add(memberType, name, attribute);
            }
        }
        return overrides;
    }

    public static T MyDeserialize<T>(string filePath)
    {
        var overrides = ReflectionAddXmlEnumAttributes(typeof(T));

        var serializer = new XmlSerializer(typeof(T), overrides);
        using (var fileStream = new FileStream(filePath, FileMode.Open, System.IO.FileAccess.Read))
        {
            var deserialized = serializer.Deserialize(fileStream);
            fileStream.Close();
            return (T) deserialized;
        }
    }

    public static void MySerialization<T>(T serializeObject, string filePath)
    {
        var overrides = ReflectionAddXmlEnumAttributes(typeof(T));
        var serializer = new XmlSerializer(typeof(T), overrides);
        using (var writer = new StreamWriter(filePath))
        {
            serializer.Serialize(writer, serializeObject);
            writer.Close();
        }
    }

For me the disadvantage of this solution is, that it's quiet much code and it then can handle only numerical types. I search for a solution, where it is possible to handle different strings for one enum literal, so it is possible to accept the numerical representation as also the name of the enum.