RIA Service 的外键问题搜集

  2010-08-25 15:23 486人阅读 评论(0) 收藏 举报

问题：在Domain Service中使用EF 4 实现如下数据访问，通过Include语句获得Job所关联的Vehicle实体

 

public IQueryable<Job> GetRunsByVehicleDate(int vehicleID,DateTime date)
        {
            date = date.Date;
            DateTime dateNext = date.AddDays(1);
            var result = this.ObjectContext.Jobs.Include("Vehicle").Include("Location").Include("TimeSlot")
                                           .Where(j => j.JobDate >= date && j.JobDate <= dateNext && j.VehicleID == vehicleID)
                                           .OrderBy(j => j.JobDate);
            return result;
         
        }

 

然而在Silverlight端，job.Vehicle 得到的却是null

 

原因：RIA没有将关联实体在客户端代码上正确生成

 

解决：使用Include 属性并修饰Job实体如下，

 

    [MetadataType(typeof(JobMetaData))]
    partial class Job : IEntity
    {

        public class JobMetaData
        {
            [Include]
            public Vehicle Vehicle { get; set; }

            [Include]
            public Location Location { get; set; }
           
        }
    }

 

注意：Include来自 System.ServiceModel.domainservices.Server.dll at path like

C:/Program Files (x86)/Microsoft SDKs/RIA Services/v1.0/Libraries/Server

 

 

问题描述: 数据库中已经设置好表的外键关系,用ado.net实体数据模型映射数据库,在Silverlight客户端始终无法访问到外键信息(返回null)   解决办法: 1.在由EF生成的XX.Designer.cs代码中,添加[Include]特性到外键属性上 2.在域服务类中,在GetXX()方法中读取外键,例如 public IQueryable<Coupon> GetCoupon() {  foreach (var cp in ObjectContext.Coupon)  {   ObjectContext.LoadProperty<Coupon>(cp, a => a.Location);  } return this.ObjectContext.Coupon.OrderBy(e => e.Coupon_ID);

 

更多例子参考：

http://www.cnblogs.com/luminji/archive/2011/06/30/2094755.html