Creating a Parameterized Query in LightSwitch

This lesson shows how to create a parameterized query in a LightSwitch application.

A parameterized query determines what data to return by evaluating one or more values (parameters) when the application runs. For example, if you set the query parameter to a product category, your query would return a list of products in that category. You can set the parameter programmatically, but most applications use parameters that reflect values that a user sets.

To create a parameterized query

  1. In Solution Explorer, open the shortcut menu for the Products.lsml node, and then choose Add Query.

    The Query Editor opens.

  2. In the Properties window, name the query ProductsByCategory.

  3. In the Query Designer, choose the Add Filter link.

  4. In the first list, choose Where.

  5. In the second list, choose CategoryID.

  6. In the third list, choose = (equals).

  7. In the fourth list, choose Parameter.

  8. In the final list, choose Add New.

    The ProductsByCategory parameterized query

    A parameter that's named CategoryID, of type Integer is created and added to the Parameters section of the Query Editor.

This lesson showed how to create a parameterized query that returns a subset of products. At run time, a CategoryID box is provided on a screen based on this query so that a user can specify a numeric value for the CategoryID parameter. For example, if the user specifies 1 in the box, all products in the Beverages category will be returned. If the user specifies 2, Condiments will be returned.

The user can type the parameter value into a text box or select it from a list. It can also be provided by another entity on a screen. For example, when a product is selected on a screen, you could use its CategoryID as a parameter to return all other products in the same category.

In the next lesson, you’ll learn how to use the parameterized query that you just created on a screen.

Next lesson: Using a Parameterized Query on a LightSwitch Screen

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