Question

我正在尝试建立一个简单的一对多关系，其中列表可以包含零个或多个任务，并且任务必须具有关联的列表。我想通过单元测试来确保这种行为，但我无法弄清楚关联是如何进行的，因此测试将失败（稍后我将使用ExpectedExceptionAttribute，但我甚至不知道将抛出哪个异常尚未）。

任务可以成功提交，但我希望看到Linq抱怨缺少List参考：

[TestMethod]
public void SavingTaskWithoutListFails()
{
    var task = new Task() { Title = "Test Task", Description = "This is the task description." };
    Db.Tasks.InsertOnSubmit(task);
    Db.SubmitChanges();            
}

我的课程和协会如下所示：

[Table]
public class Task
{
    [Column(AutoSync = AutoSync.OnInsert, DbType = "Int NOT NULL IDENTITY", IsDbGenerated = true)]
    public int TaskId { get; set; }

    [Column(IsPrimaryKey = true)]
    public string Title { get; set; }

    [Column]
    public string Description { get; set; }

    [Column]
    public int ListId { get; set; }

    private EntityRef<List> _list;

    [Association(Storage = "_list", ThisKey = "ListId")]
    public List List
    {
        get { return _list.Entity; }
        set { _list.Entity = value; }
    }
}

和此：

[Table]
public class List
{
    [Column(AutoSync = AutoSync.OnInsert, DbType = "Int NOT NULL IDENTITY", IsDbGenerated = true)]
    public int ListId { get; set; }

    [Column(IsPrimaryKey = true)]
    public string Title { get; set; }

    private EntitySet<Task> _tasks;

    [Association(Storage = "_tasks", OtherKey = "TaskId")]
    public EntitySet<Task> Tasks
    {
        get { return _tasks; }
        set
        {
            if (_tasks == null)
            {
                _tasks = new EntitySet<Task>();
            }
            _tasks.Assign(value);
        }
    }
}

任何人都可以帮助正确关联或提示如何实现所需的行为吗？

Answer 1

您应该使用[Column(CanBeNull = false)]来获得关联列。

编辑：

[Table]
public class Task
{
    [Column(IsPrimaryKey = true, AutoSync = AutoSync.OnInsert, DbType = "Int NOT NULL IDENTITY", IsDbGenerated = true)]
    public int TaskId { get; set; }

    [Column]
    public string Title { get; set; }

    [Column]
    public string Description { get; set; }

    [Column(CanBeNull =  false)]
    public int ListId { get; set; }

    private EntityRef<List> _list;

    [Association(Storage = "_list", ThisKey = "ListId", IsForeignKey = true, OtherKey = "ListId")]
    public List List
    {
        get { return _list.Entity; }
        set { _list.Entity = value; }
    }
}

[Table]
public class List
{
    [Column(IsPrimaryKey = true, AutoSync = AutoSync.OnInsert, DbType = "Int NOT NULL IDENTITY", IsDbGenerated = true)]
    public int ListId { get; set; }

    [Column]
    public string Title { get; set; }

    private EntitySet<Task> _tasks;

    [Association(Storage = "_tasks", OtherKey = "TaskId", ThisKey = "ListId")]
    public EntitySet<Task> Tasks
    {
        get { return _tasks; }
        set
        {
            if (_tasks == null)
            {
                _tasks = new EntitySet<Task>();
            }
            _tasks.Assign(value);
        }
    }
}

我将两个表的IsPrimaryKey移至Id而不是Title，将关联的一侧设为IsForeignKey=true并填充ThisKey和{{ 1}}用于结合的双方。当我尝试添加没有ListId值的新任务时，SubmitChanges抛出了SlqCEException，并显示以下消息：OtherKey

如何确保EntityRef不能为空？

1 个答案: