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Creation Of Data Entity In Light Switch 2011

In this tutorial I will explain how to create new data entities. Data entities are just like tables in databases.

Software Requirements

Visual studio 2010 ultimate(or premium)
Visual studio 2010 service pack 1
Silverlight 5 exe which you will get from http://go.microsoft.com/fwlink/?LinkID=198365
Light switch 2011 which you can download from http://www.microsoft.com/visualstudio/en-us/lightswitch

Implementation

First step is to open the visual studio 2010 and create a new project using File – New project. When you click on "New Project" option a popup will appear. Select Light Switch Application(Visual C#) from visual studio installed templates

Picture showing the lightswitch application from the visual studio installed project templates

Click to Enlarge

Enter the name of the project(Creation_Of_Data_Entity in this case), select the location and click Ok. A new project is created at the specified location.

To create a new table(Data Entity) click on the link "Create New Table"

Picture showing create new table link to create a table in the lightswitch application

Click to Enlarge

Note - Check the folder structure in the solution explorer. There are 2 folders Data Source and Screen. The former one will store all the entities and the later one will store all the screens.

When you click on the link Light Switch Entity Designer will be shown with the default name Table1Item. You can rename the table as per your requirements. Just click on the table and type the desired name

Picture showing renaming the table name from the Table1Item to Employee

Click to Enlarge

Here I have renamed the table to Employee. See the image above, there is an identity field called Id. This is primary key for the table which acts as unique identifier.

Now add fields in the table. Click on the < Add Property > write the name of the columns with the data type.

Picture showing the fields added in the lightswitch tables

Click to Enlarge

There are three fields in the table FirstName, LastName and Dept. Out of the three fields FirstName and Dept are required.

Now add another table. The purpose of adding another table is to show you how to create relations between the table. To create a new table add the New Table button as highlighted in the figure above. This time I am creating a table Department.

Picture showing Relationship button for adding the relationship between the tables

Click to Enlarge

Now we have 2 tables Employee and Department, we can add relationship between the two tables. For doing that click on Relationship… button as highlighted in the figure above.

When you click on the button a new pop up window will be opened as shown in the figure below

Click to Enlarge

Here we have 2 sections From and To. In the From section I have selected Department table and in the To section I have selected Employee table. The next section is Multiplicity. There are three options in the Multiplicity dropdown i.e. one, zero or one and many.

Scenarios

Section	Name	Multiplicity
From	Department	One
To	Employee	Many

It means one department have many employees.

Section	Name	Multiplicity
From	Department	Zero or one
To	Employee	Many

It means that Department must have one employee. But employee may have zero or one department.

Next option is On Delete Behavior. This drop down contains three options Restricted, Cascade Delete and Disassociate.

Scenarios

Department	On Delete Behavior	Description
Department	Restricted	Records in Department cannot be deleted if there is any associated record present in Employee table
Employee	NA

Department	On Delete Behavior	Description
Department	Cascade Delete	If any record in Department is deleted then delete all the associated records from the Employee table also.
Employee	NA

Department	On Delete Behavior	Description
Department	Disassociate	If the records in Department table deleted then the records in Employee table will remain intact.
Employee	NA

Finally we have Navigation property. I will explain this property in the further chapters. Once you have set all the click Ok. A relationship is formed as shown in figure below.

Picture showing the relationship established between the tables in lightswitch

Click to Enlarge

Error

When you run the application you may encountered this error

An error occurred while establishing a connection to SQL Server instance '.\SQLEXPRESS'. Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. C:\ProgramFiles\MSBuild\Microsoft\VisualStudio\LightSwitch\v1.0\Microsoft.LightSwitch.targets

To fix this issue you can do the

Step One

Open task manager and kill all the SQLServr.exe processes. Open run and write %AppData% and click enter. Your application data folder will open. Click on Microsoft – Microsoft SQL Server folder and delete all the temporary files.

Step Two

Open run and write services.msc and press enter. Service window will open. Restart all the sql server related service.

Posted By -	Karan Gupta

Posted On -	Monday, December 19, 2011

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