Displaying Local Information in a LightSwitch Application

Article
03/27/2017

For the latest documentation on Visual Studio 2017, see Visual Studio 2017 Documentation.

In this lesson, you’ll learn how to how to customize a screen in a LightSwitch application by adding a local property. A local property displays information that in’t in a data source.

Adding a Local Property

You can use the Screen Designer not only to customize the controls on a screen, but also to add data items. For example, you can add a local property that can display a calculated value.

To add a local property

In Solution Explorer, open the shortcut menu for the BrowseOrders.lsml node, and then choose Open.
On the toolbar, choose the Add Data Item button.
In the Add Data Item dialog box, choose the Local Property option button. In the Type list, choose Integer, and then choose the OK button.

A new node named Property1 is added to the left pane of the Screen Designer.
Choose the Property1 node. In the Properties window, choose the Name property, and then enter NumberOfOrders.

The name also changes in the left pane of the designer.
In the Screen Designer, drag the NumberOfOrders node just below the Command Bar node in the center pane.
Run the application and open the Browse Orders screen.

Notice that a Number of Orders label is now displayed below the screen name, and that no value is displayed.
Close the application and return to design mode.

To display a value for a local property

In the left pane of the Screen Designer, choose the Orders node.
On the ToolBar Ribbon, in the Write Code list, choose created.

The Code Editor opens and displays the created method.
In the created method, add the following code.
```
myapp.BrowseOrders.created = function (screen) {  
    screen.getOrders().then(function (results) {  
        screen.NumberOfOrders = screen.Orders.data.length;  
    })  
};  
```
When the screen is created, this code calculates the number of orders in the Orders entity. That value is then displayed in the Number of Orders field.
Run the application and open the Browse Orders screen.

Notice that the number of orders appears in the Number of Orders field.
Close the application and return to design mode.

Closer Look

This lesson showed how to create a local property to display a calculated value on a screen. In this case, you used the created method of the orders collection to return the total number of orders in the Orders entity. The code uses a Promise object to make sure that the data is loaded before returning the value of the screen.Orders.data.length property.

In addition to using a local property to display a calculated value, you can also use a local property to collect an input value from the user. For example, you could create a local property that displays a list of cities when a user specifies a geographical region.

Next Steps

In the next set of lessons you’ll learn how to create and use queries to control what is displayed on a screen.

Next lesson: Filtering Data with Queries