Enforce constructor called only from Serialization

Question

In our codebase any classes that need to be saved are IXmlSerializable, this means that they all have public parameterless constructors.

The problem with this, is I have to stick a remark above each one "Only for serialization purposes" because certain members on these instances are private and required, and are therefore required when calling all the 'usable' constructors.

What would be really nice is a way of saying "This constructor must only be called by serialization code/assemblies, otherwise I'm going to explode". Anyone know if there's a nice way to do this? They only way I can think of this is checking the call stack why sounds too expensive...

score 3 · Accepted Answer · answered Jul 19 '11 at 09:24

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How about:

    [Obsolete("Is your name XmlSerializer? No, I didn't think so.", true)]
    public Foo() { }

Note: this won't protect you from reflection, or from generics with the where T : new() constraint, but it avoids the more likely new Foo() scenario.

answered Jul 19 '11 at 09:24

Marc Gravell

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I believe xml serialization ignores properties marked as obsolete. Is it the same with constructors? – bottlenecked Jul 19 '11 at 09:27
That's pretty neat as usual. Thanks Marc :) – Ian Jul 19 '11 at 09:45

score 1 · Answer 2 · answered Jul 19 '11 at 09:44

1

I have another solution for you: move your 'private' constructor out of your class, and use a serialization surrogate - that way your magic constructor will never be used outside of serialization as it's now part of the serialization process per se.

answered Jul 19 '11 at 09:44

Florian Doyon

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I did state that this was XmlSerialization. I'm not sure that you can use the surrogate with Xml. – Ian Jul 19 '11 at 09:56
You are right, XmlSerialization cannot use this approach, although Data Contracts can. Sorry. – Florian Doyon Jul 19 '11 at 10:08

Enforce constructor called only from Serialization

2 Answers2