In this article I describe the LightSwitch development environment in Visual Studio 2012. We can easily create a LightSwitch application using Visual Studio LightSwitch 2012.

LightSwitch Development in Visual Studio 2012

Visual Studio LightSwitch automatically creates the User Interface for a DataSource without manually writing any code.

In order to begin our work with LightSwitch 2012 we will perform the following steps:

Step 1

1. Open the Visual Studio 2012.
2. Go to "File" => "New" => "Project..."
3. In "New Project" => "Installed" => "Template"
4. In "Template" => "LightSwitch"
5. Select "LightSwitch Application (Visual C#)".
6. Enter the Name and choose the location.
7. Click "OK".

Step 2

After creating the project a LightSwitch Designer will appear on the screen.

LightSwitch Designer consists of the following two options:

- we can create a new table for our application.
- we can also attach an external database. 

Step 3

Now we will see that Solution Explorer consists of a list of the following items along with two folders:

- Data Sources
- Screens

Here the "Data Sources" folder is used to store user data i.e. "Database Tables" and the "Screens" folder is used where we can create the user interface for our application.

Step 4

When we click on "Create new table" we will get the following image:

Each table consists of an "Id" that is automatically assigned and is also a "Primary Key" of the table.

Step 5

First we will rename the title of the table from "Table" to "ContactTable". Now we will add four additional columns called "Name", "Email", "Age" and "Address" to our table.

Step 6

In order to insert the record we need to create a User Interface screen. When we right-click on the "Screens" Folder we will click on "Add New." It will open the "Add New Screen" dialog window. As the window opens we will select "New Data Screen" from the Screen Template, we will also provide a Screen Name to our screen and choose the database table.

In order to continue we will Click on the "Ok" button. This will create a new UI screen for inserting a new data record by a user.

"Properties" are those where you set properties for various items.

Step 7

When we run the UI screen we get the following.

Step 8

Now we are able to insert a new record without writing any code. We don't need to create anything since Visual Studio LightSwitch automatically creates the screen for us with "Save" and "Refresh" buttons.

Step 9

In the following step we insert a record of another user; for that we create a new contact table.

Step 10

In Light Switch validations are automatically applied to the table. We do not need to apply any kind of validation on their own.

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This post discusses the new language features that is introduced in Visual Studio 2012. One of the main things that language team introduced is the idea of producing windows 8 App. These APPs are talking to new API called windows runtime.

This release also brings iterators to Visual Basic. The main discussion in this post is around Asynchronous programming in C# language.



If you want to give importance on responsiveness of client and scalability in server App then you probably call Asynchronous API’s. These API’s take Callbacks as parameters and uses that Callback to notify you about result of available. When you start write these call backs then it is harder maintain the code but with new Async language support that introduced in Visual Basic and C# and it is easy consume these API’s.

Below is the synchronous code in C#



The code basically Searches the movie index in Netflix using OData by taking Year as parameter. While it is downloading the movies using above code , you can notice you can not interact with your user interface. You can scroll along UI and explore the movies only after the search operation is complete. Users expects more responsive apps.

Why the above code is Unresponsive?

The call to DownloadString is of webclient type and it asks you to wait till it returns string. During this process your UI is going to hang-up and holds the thread until it returns the result back you.

Two different options here, you can put this code on background Thread and it is bit complicated. You may have to marshal and unmarshal the code. The second option is to interact with Asynchronous API there you have an overloaded function DownloadStringAsync, But when you use this method you are no longer take back data as result. You need to sign-up a call-back when a result is available. If you have multiple Async calls then you have to write multiple call-backs. In this case your code is getting more difficult to understand.

Solution

The new overload method is DownloadStringTaskAsync, This method now returns string of type Task, Task of string is object that notify you when result is available. Now you can change the signature of the method QueryMovies and mark this as async. This tells the compiler that this method is pausable and resumeable , they can wait without locking to the UI thread. Now change the return type of method from Movie array to Task<Movie[]> array. Write a word await to get the string from Task of objects from DownloadStringTaskAsync call.



Now you can call the above even from while loop



The compiler is now able to figure out how to handle the await inside the while loop and resume it when it gets the result. Now you should be able to interact with your UI without any hang-ups.