WCF RIA Services provides the DomainDataSource control to simplify the interaction between the user interface and data from a domain context. With the DomainDataSource, you can retrieve, shape, and edit data using only declarative syntax. You specify the domain context to use with the DomainDataSource, and then call the operations that are available through that domain context.
Configuring the Silverlight Application for DomainDataSource
To use the DomainDataSource control, you must add a reference in the Silverlight project to the System.Windows.Controls.DomainServices assembly. This reference is automatically added when you drag the DomainDataSource from the Toolbox. Optionally, to use the DataGrid with DomainDataSource, you must also add a reference to System.Windows.Controls.Data. This reference is also added automatically when you drag the DataGrid control from the Toolbox.
The host control, such as the UserControl, must contain the following namespace reference:
Optionally, to use the DataGrid control with DomainDataSource, you must also add the following namespace:
To define the domain context in declarative code, you must include the namespace of the server project. In the following example, ExampleApplication.Web is the name of the server project. You will use the name of your server project.
Retrieving and Displaying Data
You specify a domain context for the DomainDataSource and provide the name of the method to use for loading data. Then you bind presentation controls like the DataGrid to the DomainDataSource. The following example shows a DomainDataSource that retrieves data from a domain context named
ProductDomainContext and displays the data in a DataGrid control. A query method called
GetProducts() must exist on the domain service for the example to work.
Adding Parameters to the Query
In some cases a query method requires parameter values. Typically, a query method requires a parameter value to filter the data that is returned. The DomainDataSource class provides the QueryParameters collection to facilitate adding parameters. The following example shows how to add parameter value with a value that is specified in the declarative text.
You can also add a parameter that uses a value from the user for the query. You bind a Parameter object to the user-input control that contains the value to use in the query. The following example shows how to specify a value from a ComboBox is used as the parameter value.
The DomainDataSource provides the SortDescriptors collection to facilitate sorting on the data. In the SortDescriptors collection, you add SortDescriptor instances that describe the values to use for sorting the collection. You can add as many SortDescriptor instances as you want to provide layers of sorting. You can specify if the data is sorted in ascending or descending order. The following example shows how to a sort descriptor to the DomainDataSource. The data retrieved from the query is sorted by values in the
When you implement paging and sorting together, include at least one SortDescriptor with its PropertyPath attribute assigned to a property that contains unique values, such as a primary key. Or add an OrderBy clause based on a property that contains unique values to the query in the DomainDataSource. If you only sort the data on a property that does not contain unique values, the return values could contain inconsistent or missing data across pages.
The DomainDataSource provides the GroupDescriptors collection to facilitate grouping the data by property values. In the GroupDescriptors collection, you add GroupDescriptor instances that define the value to use for grouping. You can add as many GroupDescriptor instances as needed.
The following example shows how to add a value to use for grouping.
The DomainDataSource control provides the FilterDescriptors collection to enable you to filter the data that is returned by the query. By adding filters, you can specify that only entities which meet the condition in the filter are loaded from the domain context. You define the logical relationship between different filters by setting the FilterOperator property on the DomainDataSource object. The FilterOperator property supports any value in the FilterDescriptorLogicalOperator enumerator.
The following example shows two filter descriptors that are connected by a logical AND statement. One filter depends on user input and one filter is specified in the declarative syntax.
When displaying a large number of entities, you may wish to provide paging in your user interface. The DomainDataSource control enables you to specify the number of entities to load and the number of entities to display on a page. New records are loaded only when the user navigates to a page that contains entities which have not been loaded. You set the PageSize and LoadSize properties to specify the parameters for paging. Then, you bind a DataPager instance to the DomainDataSource to implement the interface for paging.
|If you use the DataPager in an application with an Entity Framework data store, you must order the data returned by your queries for the DataPager to work correctly. The Entity Framework does not support paging of data without an OrderBy clause in the query method or sorting specified on the Silverlight client.|
The following example shows paging with the DomainDataSource.