Get the DomainService (LINQ to SQL) to load child entities with .NET RIA Services in Silverlight 3

If you have a table with related tables then you can get the child entries by editing the DomainService and the metadata:
Add the include attribute ([Include()]) to the property containing the child table reference and use the DataLoadOptions to specify the child tables to include in the query result view.

In this case a Task table contains a reference to a Project table and the Project table contains a reference to the Customer table:

The domainservice class TTSDomainService

// TODO: Consider
// 1. Adding parameters to this method and constraining returned results, and/or
// 2. Adding query methods taking different parameters.
public IQueryable<Task> GetTasks()
{
    // Define the child entries to get
    DataLoadOptions options = new DataLoadOptions();
    options.LoadWith<Task>(t => t.Project);
    options.LoadWith<Project>(p => p.Customer);
    this.DataContext.LoadOptions = options;

    // Get the tasks ordered by customer, project, task
    return from t in this.DataContext.Tasks
                 orderby t.Project.Customer.Name, t.Project.Name, t.Name
           select t;
}

The domainservice meta data class: TTSDomainService.metadata.cs

// The MetadataTypeAttribute identifies TaskMetadata as the class
// that carries additional metadata for the Task class.
[MetadataTypeAttribute(typeof(Task.TaskMetadata))]
public partial class Task
{

    // This class allows you to attach custom attributes to properties
    // of the Task class.
    //
    // For example, the following marks the Xyz property as a
    // required field and specifies the format for valid values:
    //    [Required]
    //    [RegularExpression("[A-Z][A-Za-z0-9]*")]
    //    [StringLength(32)]
    //    public string Xyz;
    internal sealed class TaskMetadata
    {

        // Metadata classes are not meant to be instantiated.
        private TaskMetadata()
        {
        }

        public Nullable<int> CategoryAbbrID;

        public int CategoryID;

        public Nullable<decimal> EstDuration;

        public Nullable<int> HourType;

        public string Name;

        [Include()]
        public Project Project;

        public int ProjectID;

        public EntitySet<TaskTimeSpan> TaskTimeSpans;
    }
}

See:

http://chriswalshie.wordpress.com/2009/08/11/masterdetail-binding-with-net-ria-services-and-the-agdatagrid/

Tags: Silverlight, WCF RIA Services