I ran into a problem with Serialization today in one of my utility classes. I have an Entity generator tool I use that generates entity classes for my business objects from the database. One of the things I do in the generated file is embed the settings of the object as an embedded XML Serialization XML string right into the generated code and bracket it with #if false/#endif. I can then simply point the tool right back at this file and it can pick up the settings directly out of the generated file.

So the tool uses a PropertyGrid to display its properties so yesterday I mucked around with the designer attributes on the various properties I added DefaultValues and Categories for everything. Recompiled went on my merry way not checking closely. Today I want to open the file and regenerate and find the tool is not picking up the original settings. Sure enough looking at the generated file I see – no embedded XML data.

So what happened is that when I made these changes to the designer attributes I munged up the attributes. I did something like this on a couple of properties:

[Description("The namespace of the generated set of DataRowContainer classes.")]

[Category("Code Generation"), DefaultValue(false)]

public string Namespace

{

    get { return this.cNamespace; }

    set { this.cNamespace = value; }

}

string cNamespace = "Entities";

Notice that DefaultValue is false instead of a string value.

This was enough to get the XmlSerialization to fail. When I ran:

XmlSerializer serializer = new XmlSerializer(typeof( EntityGenerator));

Serialization immediately failed complaining that string cannot be compared to a bool value. I say this casually now, but at the time I had no clue where the error was coming from. How do you debug this when some presumably black box code basically blows up?

Well, the black box code is not quite so black box actually. Obviously this is a type construction problem that happens when the object is initially constructed in the serialization assembly, but very difficult to track down because the error message doesn’t give a lot of information.

XmlSerialization usually works with dynamic code generation and compilation. In fact, when you create an XmlSerializer it actually creates a class and then compiles it. The class is generated in your temp directory and you can pick it up there. For more exact details you can check out this post from Scott Hanselman that shows exactly how to do this.

The key thing is that you can add a configuration setting to your applications config file which causes the serialization assembly to be generated and saved.