Question

When developing I like to have strongly typed objects for certain values. An example could be a username. I’ve managed to create these value objects with validation of business rules in the constructor (the objects are immutable), but I when serializing these objects they behave funky.

[DebuggerDisplay("{Value}")]
public class Username
{
    private readonly string value;

    public Username(string value)
    {
        if (string.IsNullOrEmpty(value))
            throw new ArgumentException("value", "Must have a value");

        if (value.Length > 50)
            throw new ArgumentOutOfRangeException("value", "Maximum length of a username is 50");

        this.value = value;
    }

    public string Value
    {
        get { return value; }
    }

    public static implicit operator string(Username username)
    {
        return username.Value;
    }

    public static explicit operator Username(string value)
    {
        return new Username(value);
    }
}

My question is: Using a serializer such as Newtonsoft Json.Net how go i get this value to be serialized as { Username:"foobar" }?

Answer 1

Never tried this but I’d guess it support type converters.

Add the TypeConverter attrib to your class and create a converter for it (from string to username and vice versa)

Newtonsoft.json.net seems to support this:
http://www.symbolsource.org/Public/Metadata/Project/Json.NET/3.5-Release-6/Release/net-3.5/Newtonsoft.Json/Newtonsoft.Json/Utilities/ConvertUtils.cs

See the portion of the code starting with
“// see if source or target types have a TypeConverter that converts …”