Question

I just realized something crazy, which I assumed to be completely impossible : when deserializing an object, the DataContractSerializer doesn’t call the constructor !

Take this class, for instance :

[DataContract]
public class Book
{
    public Book()
    { // breakpoint here
    }

    [DataMember(Order = 0)]
    public string Title { get; set; }
    [DataMember(Order = 1)]
    public string Author { get; set; }
    [DataMember(Order = 2)]
    public string Summary { get; set; }
}

When I deserialize an object of that class, the breakpoint is not hit. I have absolutely no idea how it is possible, since it is the only constructor for this object !

I assumed that perhaps an additional constructor was generated by the compiler because of the DataContract attribute, but I couldn’t find it through reflection…

So, what I’d like to know is this : how could an instance of my class be created without the constructor being called ??

NOTE: I know that I can use the OnDeserializing attribute to initialize my object when deserialization begins, this is not the subject of my question.

Answer 1

DataContractSerializer (like BinaryFormatter) doesn’t use any constructor. It creates the object as empty memory.

For example:

    Type type = typeof(Customer);
    object obj = System.Runtime.Serialization.
        FormatterServices.GetUninitializedObject(type);

The assumption is that the deserialization process (or callbacks if necessary) will fully initialize it.