使用 Linq to SQL 自定义实现 DomainService

Question

任何人都可以给我举一个例子或简要描述如何使用 Linq to SQL 作为数据访问层来创建 WCF RIA 服务 DomainService 的自定义实现，但不使用.dbml 文件（这是因为 Linq to SQL 模型是由自定义工具生成的，经过大量定制，并且是一个包含 50 多个表的相当大的数据库）并且没有 VS2010 向导来创建一个DomainService（该向导依赖于可用的 .dbml 文件）

这是我迄今为止尝试过的一个非常简单的外壳：

[EnableClientAccess()]
public class SubscriptionService : DomainService
{
    [Query(IsDefault = true)]
    public IQueryable<Subscription> GetSubscriptionList()
    {
        SubscriptionDataContext dc = new SubscriptionDataContext();
        var subs = dc.Subscription.Where(x => x.Status == STATUS.Active)
            .Select(x => 
            new Subscription
            {
                ID = x.ID,
                Name = x.Name
            }).ToList();

        return subs.AsQueryable();
    }

    public void InsertSubscription(Subscription sub)
    {
        if (!sub.ID.IsEmpty())
        {
            SubscriptionDataContext dc = new SubscriptionDataContext();
            Subscription tmpSub = dc.GetByID<Subscription>(sub.ID);
            if (tmpSub != null)
            {
                tmpSub.Name = sub.Name;
                dc.Save(tmpSub);
            }
            else
            {
                tmpSub = new Subscription();
                tmpSub.Name = sub.Name;
                dc.Save(tmpSub);
            }
        }
    }

    public void UpdateSubscription(Subscription sub)
    {
        if (!sub.ID.IsEmpty())
        {
            SubscriptionDataContext dc = new SubscriptionDataContext();
            Subscription tmpSub = dc.GetByID<Subscription>(sub.ID);
            if (tmpSub != null)
            {
                tmpSub.Name = sub.Name;
                dc.Save(tmpSub);
            }
        }
    }

    public void DeleteSubscription(Subscription sub)
    {
        if (!sub.ID.IsEmpty())
        {
            SubscriptionDataContext dc = new SubscriptionDataContext();
            Subscription tmpSub = dc.GetByID<Subscription>(sub.ID);
            if (tmpSub != null)
            {
                dc.Delete(tmpSub);
            }
        }
    }
}

到目前为止，这似乎有效。有人发现我可能遗漏的这种方法有什么问题吗？如果有人已经尝试过这种方法并发现了一些重大问题，我不想在错误的道路上走得太远。

感谢大家的意见。

Answer 1

这样做并没有什么错。

我也做过基本上同样的事情。

您将需要创建一个为每个查询返回 IQueryable 的属性，并且您将使用 RIA 服务自动神奇地获取“skip/take/where”内容。

[EnableClientAccess()]
public class SubscriptionService : DomainService
{
    [Query(IsDefault = true)]
    public IQueryable<Subscription> GetSubscriptionList()
    {
        using(var dc = new SubscriptionDataContext())
             return from x in dc.Subscription
                    where x.Status == STATUS.Active
                    select new Subscription { ID = x.ID, Name = x.Name };
        // make sure you don't call .ToList().AsQueryable() 
        // as you will basically load everything into memory, 
        // which you don't want to do if the client is going to be using 
        // any of the skip/take/where features of RIA Services.  
        // If you don't want to allow this, 
        // simply return an IEnumerable<Subscription>
    }
 }

我假设 Subscription 是 DTO 而不是 L2S 类，因为您正在显式实例化它。只需确保您的 DTO 具有正确的属性即可。即，

public class Subscription
{
    [Key]
    // you must have a key attribute on one or more properties...
    public int ID { get; set; }
}

如果您的 DTO 中有子元素，请使用 Include 和 Association 属性：

public class User
{
    [Key]
    public int Id { get; set; }

    [Include]
    [Association("User_Subscriptions", "Id","UserId")]
    // 'Id' is this classes's Id property, and 'UserId' is on Subscription
    // 'User_Subscriptions' must be unique within your domain service,
    // or you will get some odd errors when the client tries to deserialize
    // the object graph.
    public IEnumerable<Subscription> Subscriptions { get; set; }
}

另外，作为旁注，您的删除方法不需要完整的对象，像这样的东西会起作用，并且会阻止客户端序列化整个对象并在您不需要时将其发回。

public void DeleteSubscription(int id)
{
    using(var dc = new SubscriptionDataContext())
    {
        var sub = dc.GetById<Subscription>(id);
        if( sub != null ) dc.Delete(sub);
    }
}