The second issue is that user controls are in their own scope and don’t have immediate access to the rest of the page. That is both a blessing and a curse; good control design means that the controls should be fairly independent of each other but a more pragmatic developer will also note that user controls exist primarily so that numerous copies of the same thing can be easily created and that making entirely self contained controls leads to a lot of unnecessary duplication.

Fortunately there are workarounds for both of these issues.

Regardless of view state, a user control can pass information and therefore trigger events properly using the ASP framework by means of some elaborate JavaScript trickery. In this example, I am using JQuery and JavaScript to allow a click event inside a ViewStateless user control to set the value of a text box and click a button outside of the control, thereby triggering an event within the ASP framework.

$(JQueryObjectForMyUserControl).find(".clickableElement")
.unbind("click").click(function() {
        var clickHandler = $(this).parents(".OuterBound").find(".ClickHandler");
        //I'm replacing the underscores with dollar signs here because that is what ASP expects to find internally
        var argument = $(this).find("a").attr("id").replace(/_/g, "$");
        clickHandler.find(".ClickHandlerArgument").val(argument);
        clickHandler.find(".ClickHandlerLinkButton").click();
    });

Getting around the scope restriction requires a great deal less insanity. For example, my user controls have to be able to activate a modal overlay and dialog box. I could put the code for that inside each user control but that would be a lot of code bloat. Instead, I have the dialog in one place on my page and allow the controls to set its values and activate it.

Page page = this.Page;
ModalPopupExtender ModalPopupExtenderLockedDialog = (ModalPopupExtender)page.FindControl("ModalPopupExtenderLockedDialog");
Label LabelMessage = (Label)page.FindControl("LabelMessage");
ModalPopupExtenderLockedDialog.Show();
LabelMessage.Text = "Hello World!";

Getting to properties is only a little harder. If you need to get to the properties of your page you need only cast this.Page appropriately.

Not this kind of XML

VirPack has me working on an application that needs a user administered list of options for people to choose from. It’s a fairly simple thing that doesn’t require relational tables so I thought I’d toss it into XML.

Now, C# deals with XML really well. Almost everything, if you just ask nicely, will be quickly and easily packed off into XML the framework with just a few lines of code.

String path = Server.MapPath("~\\myfile.xml");
using (FileStream sourceFile = new FileStream(Server.MapPath(path), FileMode.Create, FileAccess.Write))
        {
            XmlSerializer serializer = new XmlSerializer(typeof(Foo));
            serializer.Serialize(sourceFile, bar);
        }
        bar = null;
        using (System.IO.FileStream sourceFile = new System.IO.FileStream(path, System.IO.FileMode.Open, System.IO.FileAccess.Read))
        {
            System.Xml.Serialization.XmlSerializer serializer = new System.Xml.Serialization.XmlSerializer(typeof(Foo));
            Foo bar= serializer.Deserialize(sourceFile) as Foo;
        }

As simple as that I’ve packed my class off to be serialized and then unserialized it. Three lines of code is hard to beat for XML serialization and deserialization. “Foo” is a user defined type, however, and my particular task being the population of a drop-down list, no such complexity was required. Yet, when I tried to feed a List of ListItems into the Serializer everything broke.

//This breaks
System.Xml.Serialization.XmlSerializer listSerializer = new System.Xml.Serialization.XmlSerializer(typeof(List));
//This too
System.Xml.Serialization.XmlSerializer typedListSerializer = new System.Xml.Serialization.XmlSerializer(typeof(List<ListItem>));

This has to do with how C# deals with collections. Serialization requires a root level node and a collection, despite having an appearance of such, has no root level information. It is a collection, not a collection bounded by something else and XML serialization requires that something else.

So C# has a hackish workaround. The ListItemContainer class is a simple type that contains a List of ListItems.

//This works
System.Xml.Serialization.XmlSerializer listSerializer = new System.Xml.Serialization.XmlSerializer(typeof(ListItemContainer));

Of course, not everything you’ll wish to serialize in a list will be a list item, but the fact that C# had to create it’s own little wrapper class should be a clue for developers. Getting a collection into XML requires a wrapper class; it’s as simple as that.

Would it have killed them to document that though?

Image Credit: PixelPlacebo via Flickr and Creative Commons

Unit testing is good; test driven development is better.  As Knuth once famously quipped “Beware of the above code. I have only proven it correct, not tested it.” There really is no substitution for good, solid testing.

Unfortunately, at least in C#, webpages don’t like to be unit tested.  I approach this post with an uncomfortable realization that I am about to lay out the issues and problems I’ve had while the solution I am presently using is far from satisfactory.

There is a right way and a wrong way to undertake a lot of unit testing.  If you want to learn about that, I recommend this post by Ryan Hagan as a great jumping off point.  My problem is not in writing good unit tests, however, so much as having a place to write them.

Axiomatic truth of Unit Testing: Your test code should exist in a different place than your production code.  This just makes good sense.  You don’t want to publish your tests every time you push code out the door and, since you want all of your published code to be tested you don’t want to have to write tests for your tests.  In C# the way one generally accomplishes this is the creation of a separate test project within the current solution.  That way the solution contains both your code and your tests.

Now generally, when you’re writing tests for C# this isn’t a big deal.  Since your project gets bundled up every time you build you can add a reference to the Test project that points at your main project; that way, the test harness knows what to make of all the custom types and whatnot that your various tests will have to evaluate.

This does not work for webpages.

When C# builds a webpage there’s no handy-dandy compiled thing at which to point your test code.  That means your test code has no idea what to make of any custom objects you’ve created and that makes any meaningful testing pretty much impossible.  Consider the following short example:

public void CreateTest()
        {
            string WidgetName = string.Empty;
            Widget expected = null;
            Widget actual;
            actual = WidgetFactory_Accessor.Create(WidgetName);
            Assert.AreNotEqual(expected, actual);
       }

In this example, “Widget” and “WidgetFactory” are both custom types.  C# has conveniently generated an accessor for my Factory but it has no reference to my main project and thus doesn’t know what a Widget is.  Consequently, this test won’t compile and I can’t run it.

There is a work-around solution I’ve found wherein I publish the Main Project and then create a reference from the Test Project to the published AppCode.dll file.  This works but requires that I publish the DLL every time I wish to re-evaluate my source code which makes the entire testing process prohibitively time consuming.

My suspicion at this point is that what I am trying to do is in fact neither possible nor recommended and that unit testing of a C# webpage should be accomplished by creating a sharp distinction between the interface and presentation layers, testing the presentation layer traditionally and then using interface testing suites like Watir.  This seems the sort of thing that should be verbosely stated somewhere if it is, indeed, the case.

Update

As per Ryan’s suggestion below and some other feedback I’ve gotten I am moving much of the logic code out of the project and creating a project-level distinction between the interface and the presentation layers of the application.  This should allow me to more sanely test the presentation layer and leverage Watin in to handle the interface testing.

It’s not the sort of separation recommended, but the architecture on this particular system is fairly dated and a full out re-factoring is out of the question (for now).

As it’s conspicuously missing from many other write-ups I’ve seen I’ll say it here.  You can not meaningfully test anything except the interface of a C# web project.  If you want to test your code, move it into a DLL project and allow your web project to call that DLL.  Ideally the Web project should be as thin as possible.

People familiar with C# know that C# supports the inclusion of user defined controls called WebControls.  These are more or less very simple C# programs which can be man-handled by another bit of C# code.  They’re handy for making your code modular: you might design a web-control that takes and validates a credit card number, for example.

But WebControls are notoriously tricky beasts and over the course of the last few weeks I’ve come to understand that one of the reasons for this is that they don’t behave quite the way you might expect them to when they are serialized and deserialized.

Most C# serialization occurs behind the scenes in something called the ViewState.  For those of you who have no idea what that means, ViewState is C#’s rather clever way of persisting the things on a webpage so that it feels a little more like a desktop application.  The long and the short of its behavior is that things get serialized into the ViewState just before rendering and de-serialized back out of ViewState on the next request as part of the load step.

Most controls go into the ViewState… but WebControls don’t.  At least, they don’t go in there by default.  Presumably you can create custom ViewState serialization for them; I have not tried this.  Instead, I serialized my WebControls very simply into Session and coded that storage into a property.  My code looked something like this

private Widget InternalWidget
{
	get
	{
		Widget result;
		if (Session["Widget" + this.UniqueID] != null)
		{
			result = Session["Widget" + this.UniqueID] as Widget;
			if (result == null )
			{
				result = WidgetFactory.Create();
				result.Arguments = InternalActivePortlet.Arguments;
			}
		}
		return result;
	}
	set
	{
		Session["Widget" + this.UniqueID] = value;
	}
}

Now, as expected, none of my EventHandlers persisted when the WebControl came back out of its session serialization.  The object that comes back from serialization is an entirely new object; the old one has been destroyed.  As a result, the event handlers in the deserialized object point to null function pointers.  C# doesn’t throw an error when you call a null function pointer, however; it just goes on its merry way and does nothing.

But the function pointers – even though they now point to null objects – remain.  C# remembers a great deal more about the session-serialized object than one might think including – and this is the part that really threw me – the fact that it’s already been through the ASP parser.

I had expected, since my event handlers weren’t working when the WebControl came back from Session, that the events themselves were gone and that therefore the object returned from session was new — as if it was programatically created for the first time.  This is not the case.  When you programatically create a WebControl for the first time it’s ASP file is parsed and event handlers are set up based upon the code there.  When you deserialize a WebControl from session, however, C# remembers that it has already dealt with its ASP code and does not do it a second time.

Consequently, none of the event handlers defined in the ASP work either.

I expect that all of this seems rudimentary to more experienced C# developers, but to me it was quite a mystery and it took me some time to work out the above logic.  Hopefully this will aid some neophyte coder working through the same issues I had.

On a totally unrelated note: I need to find a decent code display plugin for WordPress…