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Using a Parameterized Query on a LightSwitch Screen

In this lesson, you’ll learn how to filter data on a screen by using a parameterized query.

In the previous lesson, you created a query to filter products based on a CategoryID parameter. At run time, you can use this parameter to apply the filter to another entity that contains a CategoryID field. For example, you can use the parameterized query to display all products that are in the same category as the product that appears on the screen.

The parameter value can be supplied as a property in the Screen Designer at design time or by the user at run time. In this example, you'll assign the value at design time.

To add a parameterized query to a screen

  1. In Solution Explorer, open the shortcut menu for the CurrentProductList.lsml node, and then choose Open.

  2. In the Screen Designer, on the toolbar, choose the Add Data Item button.

  3. In the Add Data Item dialog box, choose the Query option button.

  4. In the Name column, choose NorthwindEntitiesData.ProductsByCategory, and then choose the OK button.

    A ProductsByCategory node appears in the left pane.

  5. Under the Query Parameters node, choose the CategoryID node.

  6. In the Properties window, choose the Parameter Binding property, and then enter CurrentProducts.SelectedItem. CategoryID.

  7. In the Screen Designer, choose the Tabs node, and then choose the Add Tab node.

    A Rows Layout | Group node appears in the screen content tree.

  8. In the Properties window, choose the Name property, and then enter RelatedProducts.

  9. In the Screen Designer, choose the Rows Layout | Related Products node. In the Add list, choose Products By Category.

    The modified Current Product List screen
  10. Run the application and open the Current Product List screen.

  11. Choose a product, and then choose the Related Products tab.

    Notice that all products that have the same CategoryID as the product you’ve selected are displayed in the tab.

In this procedure, you used the parameterized query that you created in the last lesson to display a list of products. The query was added to an existing screen, the Current Product List screen. The Parameter Binding property of the query specifies the CategoryID value for the selected item from the existing CurrentProducts collection on the screen and supplies the parameter at run time. As a result, a list of products that have a matching CategoryID is displayed every time the user selects a product in the CurrentProducts list.

In the next set of lessons, you’ll learn how to work with menus and commands.

Next lesson: Creating Commands and Working with Menus in LightSwitch

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