Ajax Webmethods, Javascript, and Anonymous Types… Booyah

As witnessed in this super awesome post I showed how to use a webmethod to get server side information with client side methods. (I know, I’m pretty sweet.) And in this one I had an example of filling a drop down list with a web method and javascript, though it was more about the anonymous method used. So what do I have now? Well a little thing about why I heart anonymous types.

What’s an anonymous type? Well it’s a type that built at compile time and requires no class file to create, but you probably have already used them if you’ve used Linq:

    var anonymous = from item in list
                    select new {
                                 Name = item.Name,
                                 Address = item.Address

And now you have a whole list of a new type that is created at compile time. Anyways, you might have been wondering why you would want these beyond linq use. Well that’s what I’m here for… that and making sure I give you a low point in your day so that things can only get better.

Now in the example from before, it was basically the idea of filling a drop down list without a postback and using a WebMethod. Now I showed the javascript needed, but I didn’t show you the web method itself.
Time to start!

        public static Object GetUserList()
            IList <User>userList;

            userList = LinqData.DataClasses.User
            return userList
                      .Select(item => new { item.UserName, item.UserID })

So there you have a method that gets some users (Waring: Actual method may vary) and you are creating a list of anonymous types that have UserName and UserID.

Now you may have noticed this:

    .Select(item => new { item.UserName, item.UserID })

Now why would I want to do that? Why can’t I just send a list of users? Well there’s nothing really stopping you from doing that, after all javascript will handle whatever you throw at it. Problem is: If you send an entire user, you’re sending everything. What if the user has an image on it? (Like an avatar) Maybe the user has a collection of addresses. Point is, that’s a lot to send out when you only need the two things. (Text and value for the dropdown list) The beauty of the anonymous types is you don’t need a new class file for the smaller version of the user thus allowing you to create a specific type that is only needed for this situation.

The nice thing to take from this is that you can easily create the bare minimum and really not sacrifice much. Why is that? Well you would think that the type is created for every user or maybe every time there is at least one instance running on the server. Fact is, the type itself is created at compile time so you don’t suffer that kind of pain. Beyond that, and I said this before, Javascript is more than capable of “reading” and “knowing” what the class has so you don’t have to worry about it needing some class off in some class file to send.

Now you could argue that you should have that class file and that it’s just good practice but I’m not convinced in this case. Mostly because this is a one time situation but, and yes it sounds funny to use “situation” again, situationally this is specific only to this instance… SITUATION

I suppose someone could argue that if I use other anonymous types elsewhere that use the same properties than I should make a new class file. There’s probably some truth to this, but on the other hand is it really necessary to go that far if you aren’t certain? I don’t know. But then again I’m fascinated by popcorn so you might not want to take my opinions seriously.