How do I return multiple generic Lists in one Web Call ?

Question

Ok, I poked around before posting and can't seem to find anything... so here we go.

I decided that returning datasets, working with datasets and datatables in a front end app is a rather bad idea. So with the magic of generics I am returning a generic list via Webservice call ( not WCF just plain ol' asmx ) . That works dandy as long as you need to return one list per call to your webservice.

The scenario I am running into is that I have a more involved screen where there are a few dropdowns and so on. I need to bind those dropdowns to a generic list. Problem is that I don't want to make several web calls, one for each dropdown, to get my data. In the past I would have just returned a dataset and bound a dropdown to a specific table in the dataset.

So, it would be super to return multiple generic lists in one web call.

Things I've tried:

1. Using a List of Lists
2. Using a Collection of generic Lists
3. Creating a base class and using a Collection of List<Base> , there are conversion issues there when trying to stuff objects into that List<Base>.
4. Creating a class that has properties that return List<MyOneObject> , List<MySecondObject> .. etc. That works but it's kinda messy... I have lots of classes and screens in the app where this would happen. I could create a class like this that has a properties of List for each class, but like I said I think that may get out of control.

So at this point I have two options, #4 in the above list, or just return a dataset which I would prefer not to do :0) Has anyone run into this before ?

Answer 1

Well I don't think returning multiple lists is a good idea, but if you are going to do it, I would create a wrapper class with each list exposed as a property in that class.

Something like

class Wrapper
{
   public List<object1> Object1List {get;set;}
   public List<object1> Object2List {get;set;}

}

Answer 2

The answer is #4, via a class, either that or multiple calls, which you would rather not do

Answer 3

Well it seems that I start all my answers today with a question? Why wouldn't you wanna do multiple calls behind the scene?

If you use one async call på dropdown/control you need to bind you'd get a more fluent user experience. (especially true for large independant lists) simply because if you only do one call all dropdown/conrtols will need to wait for all the other contrls data to be returned.

That being said: If the lists you're returning a close to each other in length youd could use a dictionary, using key to represent "property name" and the value to well represent the value. Very little code require and converting what ever the source is to a dictionary with .ToDictionary() is pretty straight forward (if the source is not IEnumerable implementing .ToDictionary() for that source is usually straight forward)

Answer 4

How do we bind now to different combo boxes ?