Serialize Composed Func?

Question

This works fine:

    Func<string, string> func1 = s => s + "func";
    ViewState["function"] = func1;

However, this does not:

    Func<string, string> func1 = s => s + "func";
    Func<string, string> func2 = s => func1(s);

    ViewState["function"] = func2;

It throws a runtime serialization exception: Type 'MyProjectName._Default+<>c__DisplayClass3' in Assembly 'MyProjectName, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' is not marked as serializable.

Now, I can work around this this time, but I'd like to understand why this is happening so that if, in the future, I have no choice but to compose functions before serialization, I'll have a solution.

Answer 1

What's happening in the second case is that a closure is involved. The use of func1 inside of func2 creates a closure to captured the shared state between the lambdas expressions. Closures are not serializable. When you try and serialize the func it tries to serialize the target object which is the closure and you get your exception.