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Default Value In Light Switch 2011

In this tutorial I will explain about how to set default value in Lightswitch.

Software Requirement

Before you start reading this tutorial you should make sure that

Visual studio 2010 is installed on your machine.
Visual Studio 2010 service pack 1 is installed on your machine.
Microsoft Visual Studio Light switch 2011 is installed on your machine.

Prerequisite Knowledge

Before you go ahead, it is required that you should know

What is lightswitch?
What are screens and entities in lightswitch?
How to create an entity in lightswitch?
How to create a screen in lightswitch?
How to work on screen designer in lightswitch application?

Why Default Value Is Required

Consider an example of a table which manages the employee data. For the audit purpose every table has a field CreatedOn and UpdatedOn field. When a record is inserted into the table, current date should be entered into CreatedOn field. To avoid the misusage these fields are kept hidden from the user, but there should be a mechanism to enter the value in the fields. Setting the default value is that option, so that when a new record enters in the table the CreatedOn field should be updated with today’s date.

Creation Of Sample Entity

For the sake of this tutorial I have created an entity Employee.

Picture showing the CreatedOn field with Display by Default checkbox unchecked

Click to Enlarge

Here CreatedOn is a field where we want to set the default value i.e. current date whenever the new record is created.

The one change that I have done is in the property window of CreatedOn field. I have unchecked the checkbox Display by Default. The reason for doing that is we don’t want to show this field in any of the screen unless we explicitly add it.

Add Default Value

To add the value click on the arrow sign on the upper right hand side of the screen and click on the option Employee_Created as shown in figure below

Picture showing invoked the Employee_Created event for the entity

Click to Enlarge

When you click on the option code window opens as shown in the figure below.

Picture showing setting the default value of the field in the Employee_Created event in code behind

Click to Enlarge

Set the value of CreatedOn property to current date as shown in figure above.

Creation Of New Data Screen

For adding a new screen

Right click on the Screens folder and click Add Screen… option.
When you click on it a new screen open up.
Select New Data Screen as screen type.
Enter Screen Name.
Select Screen Data.
Uncheck Employee Details checkbox.
Click Ok.
A new screen will be added to the solution.

Picture showing adding the new screen in the lightswitch application

Click to Enlarge

Designer View Of New Data Screen

When a new screen is added into the solution the designer view is opened as shown in figure below.

Picture showing th designer window of the new screen in lightswitch

Click to Enlarge

Here there is no CreatedOn field as we had unchecked the checkbox Display by Default in the property window.

Creation Of Search Data Screen

For adding a new screen

Right click on the Screens folder and click Add Screen… option.
When you click on it a new screen open up.
Select Search Data Screen as screen type.
Enter Screen Name.
Select Screen Data.
Click Ok.
A new screen will be added to the solution.

Click to Enlarge

Designer View Of Search Data Screen

In the designer screen again there is no CreatedOn field for the same reason. To add the field drag the field onto the command bar and then change the control type from calendar to label.

Picture showing adding the CreatedOn field dropped on the designer window

Click to Enlarge

Add New Data

Run the program
Enter the details.
Click Save.
Data is entered into the table.

Picture showing the Save button for saving the record

Click to Enlarge

As you can see in the screen above there is no way for the user to enter CreatedOn date, it is inserted into automatically.

Search Screen

Click on the Search Employees screen.

Picture showing the CreatedOn field on the grid with the default value

Click to Enlarge

Here today’s date is entered automatically by default.

Conclusion

Default value ensures the field is not tampered by the user and still enters the value that you specify as default into the field.

Posted By -	Karan Gupta

Posted On -	Tuesday, January 24, 2012

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