Master-detail relation in LINQ to SQL for Windows Phone 7.1

masterdetaildb.cs

using System;
using System.ComponentModel;
using System.Data.Linq;
using System.Data.Linq.Mapping;
using System.Linq;
using Microsoft.Silverlight.Testing;
using Microsoft.VisualStudio.TestTools.UnitTesting;

namespace blah
{
    public class TestDb : DataContext
    {
        public TestDb(string connectionString) : base(connectionString)
        { }

        public Table<Master> Masters;
        public Table<Detail> Details;
    }

    [Table]
    public class Master
    {
        private int _id;
        [Column(IsPrimaryKey = true, IsDbGenerated = true, DbType = "INT NOT NULL Identity", CanBeNull = false, AutoSync = AutoSync.OnInsert)]
        public int Id
        {
            get { return _id; }
            set { _id = value; }
        }

        private string _title;
        [Column(CanBeNull = false)]
        public string Title
        {
            get { return _title; }
            set { _title = value; }
        }

        private EntitySet<Detail> _details;
        [Association(Storage = "_details", OtherKey = "_masterId", ThisKey = "Id", DeleteRule = "CASCADE")]
        public EntitySet<Detail> Details
        {
            get { return _details; }
            set { _details.Assign(value); }
        }

        public Master()
        {
            _details = new EntitySet<Detail>(
                detail => detail.Master = this,
                detail => detail.Master = null);
        }
    }

    [Table]
    public class Detail
    {
        private int _id;
        [Column(IsPrimaryKey = true, IsDbGenerated = true, DbType = "INT NOT NULL Identity", CanBeNull = false, AutoSync = AutoSync.OnInsert)]
        public int Id
        {
            get { return _id; }
            set { _id = value; }
        }

        private string _title;
        [Column(CanBeNull = false)]
        public string Title
        {
            get { return _title; }
            set { _title = value; }
        }

        [Column(CanBeNull = false)]
        internal int _masterId;

        private EntityRef<Master> _master;
        [Association(Storage = "_master", ThisKey = "_masterId", OtherKey = "Id", IsForeignKey = true, DeleteOnNull = true)]
        public Master Master
        {
            get { return _master.Entity; }
            set
            {
                Master previousValue = _master.Entity;
                if ((previousValue != value) || (_master.HasLoadedOrAssignedValue == false))
                {
                    if (previousValue != null)
                    {
                        _master.Entity = null;
                        previousValue.Details.Remove(this);
                    }

                    _master.Entity = value;
                    if (value != null)
                    {
                        value.Details.Add(this);
                        _masterId = value.Id;
                    }
                }
            }
        }
    }

    [TestClass]
    public class UnitTests : SilverlightTest
    {
        private readonly String KDBConnectionString = "Data Source=isostore:/testdb.sdf";

        [TestMethod]
        [Microsoft.VisualStudio.TestTools.UnitTesting.Description("TestDb")]
        public void TestDb()
        {
            using (TestDb db = new TestDb(KDBConnectionString))
            {
                if (db.DatabaseExists())
                {
                    db.DeleteDatabase();
                }

                db.CreateDatabase();
                Assert.IsTrue(db.DatabaseExists(), "Setup failed");

                db.Masters.InsertOnSubmit(new Master() { Title = "M" });
                db.SubmitChanges();
                Assert.IsTrue(db.Masters.Count() == 1, "No master created");

                db.Details.InsertOnSubmit(new Detail() { Title = "D1", Master = db.Masters.First() });
                db.SubmitChanges();
                Assert.IsTrue(db.Details.Count() == 1, "No details created");
                Assert.IsTrue(db.Masters.First().Details.Count() == 1, "No detail in master");
                Assert.IsTrue(db.Masters.First() == db.Details.First().Master, "Master mismatch");

                db.Masters.First().Details.Add(new Detail() { Title = "D2" });
                db.SubmitChanges();
                Assert.IsTrue(db.Details.Count() == 2, "2nd detail not created");
                Assert.IsTrue(db.Masters.First().Details.Count() == 2, "2nd detail not added to master");

                db.Masters.DeleteOnSubmit(db.Masters.First());
                db.SubmitChanges();
                Assert.IsTrue(db.Masters.Count() == 0, "Master delete failed");
                Assert.IsTrue(db.Details.Count() == 0, "Cascaded detail delete failed");

                db.DeleteDatabase();
                Assert.IsFalse(db.DatabaseExists(), "Cleanup failed");
            }
        }
    }
}