24 Sep 2013

LightSwitch: Passing data between screens - Example 5: Passing information to an "add" screen

For other posts in this series, see our series list.

In the previous examples, we have always passed data to a simple browse screen. Passing to a screen where you add an item is a little more complex so we will look at how to solve that. It may also seem that what we did in example 3, wasn’t useful since example 4 showed a better way – however there are times you can’t do that so we will also look at that. Finally we will end with a better way to do this, using a b

This posts, and the rest in the series will be a bit shorter as we are covering the same theme but applied in different ways – so make sure you read the preceding parts or you may feel a bit lost.

As with each part of this series, the code can be found on GitHub.

Example 5a: Passing information to an “add” screen with JavaScript

1. On our add screen we start by adding a data item. We will name it Animal and we will set the Type to Integer. The point of using Integer is to show that the type of the property doesn’t matter to JavaScript. Setting it to a different type than we expect, only affects the tooling.  Lastly we set this to be a parameter.


2. Now we will do the code for the create event, and here we need to do two things. As this is a “add” screen, the first bit of code is to make sure we have an object defined. AnimalInfo is the object that the screen monitors and will persist to the backend – so if it is not defined (null) we must create our own.  We do that with:

if (screen.AnimalInfo == null){
    screen.AnimalInfo = new myapp.AnimalInfo();

And then we follow that up with the simple line of of assigning the name of the animal from our data item: screen.AnimalInfo.AnimalName = screen.Animal;

Note: even though we set the property which is of type string, to an integer – it just works.


3. I mentioned the tooling becomes a problem if we do not use the right types, so to see how that occurs – we add a button to the browse screen (that we used in the last example) and try to open it up our screen and set the name, however Visual Studio doesn’t let us.


4. We can just work around this in code, and we start off on the browse screen by adding a button with the method named ShowAnimalInfo


5. The code we use in the button is very simple: myapp.showAddAdnimalInfo(null, screen.AnimalsSet.selectedItem.Name);

This should look very similar to example 4, except we have a null in the first parameter (since we want the add screen to create the object associated with the screen – which we covered in step 2). The second parameter is passing the selected items name to the screen. Once again, the tooling is expecting an integer but JavaScript is dynamic so it will accept a string.


6. That’s it! It all just works!

Example 5b: Passing information to an “add” screen – working with the tooling

This final example, is to show you just how nice the tooling is when you pass the right types around and how you can do the same as above without JavaScript. If you are looking at the demo code, this is in the AddAnimalsInfoSmart screen.

1. The major different here is the type of the data item we add as a parameter. So for this we set the type to the Animals (Entity).


2. Now we need to write a bit of code again on the create event. Since we are only going to use the tooling to launch this screen, we do not need the check to see if the object for the screen is set. All we need to do is set the values.


3. Finally the button on the browse screen is just added using VS without JavaScript & we can use the IntelliSense to select the right things:


This second route is WAY better and what I recommend using, but it is great to know if you find yourself in a situation with two types that don’t match up you can work around it with a trivial amount of code.

16 Sep 2013

LightSwitch: Passing data between screens - Series List

This page is used to list the parts of my series on how to pass data between screens. Some of these aren’t up yet, so they are not linked. As soon as they are available they will be linked here!

As with all post in this series, you can get the code for this from GitHub.

16 Sep 2013

Creating Web Pages Using the LightSwitch HTML Client in Visual Studio 2012

imageMy friend and fellow MVP Michael Washington runs THE LightSwitch website, and recently he published a book, Creating Web Pages Using the LightSwitch HTML Client in Visual Studio 2012, with and I decided to buy a physical copy to show my apparition of his great work. I thought I would take some time to write a brief review of thebook.

The question I always ask for a review, is this the book for me – the answer is YES! This book is for EVERYONE! However, let us dig into some more details on the book.

Newbies to LightSwitch

If you are new to LightSwitch, or new to the HTML client, then the book covers a lot of the things you need to think of. Each chapter covers in a very practical way how to implement what it showing and it is very visual in how it covers the material. What is great is this book doesn’t shy away from the developer aspects, and there is plenty of coverage on the JavaScript development models and how to put it together.

This is so good for newbies, that I think Michael should license this to Microsoft so they can build training material around it!

LightSwitch Professionals

I have done LightSwitch for years from the smallest projects to massive things and everything in between – and even I saw & learnt things. A lot of what I personally gain was ideas of how to put content together and ideas on JavaScript libraries. I literally went to work the next day after the book, and submitted a list of ideas inspired by the book!

Where the book is weak

The book isn’t perfect though – where it falls down is the later bits, most glaringly a section on using a WCF RIA Service with it. RIA Services, with the death zombie-ness of Silverlight (in my view) and LightSwitch does support WebAPI which is what ASP.NET is pushing & is the future (in my view) & there is no Web API material. 

The only other problem, is that the images are in grey scale. While reading it didn’t annoy me but when I closed it, and realised the final example image is the image on cover… I realised how much I lost not having colour images.