c# - 使用 Linq to SQL 自定义实现 DomainService

Question

谁能给我指出一个示例或简要描述如何使用 Linq to SQL 作为数据访问层但创建 WCF RIA Services DomainService 的自定义实现使用 .dbml 文件(这是因为 Linq to SQL 模型是由自定义工具生成的，高度自定义，并且是具有 50 多个表的相当大的数据库)并且没有 VS2010用于创建 DomainService 的向导(该向导取决于可用的 .dbml 文件)

这是我到目前为止自己尝试过的一个非常简单的 shell:

[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。有没有人看到我可能遗漏的这种方法有任何问题？如果有人已经尝试过这种方式并发现它存在一些主要问题，我不想在错误的道路上走得太远。

感谢大家的意见。

Answer 1

这样做没有错。

我基本上做过同样的事情。

您将需要为每个查询创建一个返回 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。只要确保您的 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; }
}

另请注意，您的 delete 方法不需要完整的对象，这样的方法可以工作，并且可以防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);
    }
}