使用导航对象进行实体框架查询答案

【问题标题】：Entity Framework Querying with Navigate Objects使用导航对象进行实体框架查询
【发布时间】：2012-03-06 12:51:19
【问题描述】：

我下面有实体类，我想要一个像 sql 这样的查询，实体框架怎么可能？？

select * from SiteUsers su
inner join SiteUserRoles sur on su.Id=sur.SiteUserId
inner join SiteRoleActions sra on sur.SiteRoleId = sra.SiteRoleId
inner join SiteActions sa on sa.Id = sra.SiteActionId
where su.Id=1 and sa.ParentId=189



  public class SiteRole
    {
        public SiteRole()
        {
            this.SiteActions = new HashSet<SiteAction>();
            this.SiteUser = new HashSet<SiteUser>();
        }

        public int Id { get; set; }
        public string Name { get; set; }
        public string Description { get; set; }

        public virtual ICollection<SiteAction> SiteActions { get; set; }
        public virtual ICollection<SiteUser> SiteUser { get; set; }
    }

 public partial class SiteUser
    {
        public SiteUser()
        {
            this.SiteRoles = new HashSet<SiteRole>();
        }

        public int Id { get; set; }
        public string Email { get; set; }
        public string UserPassword { get; set; }
        public string UserName { get; set; }
        public string LastName { get; set; }
        public string FirstName { get; set; }
        public Nullable<System.DateTime> DateCreated { get; set; }

        public virtual ICollection<SiteRole> SiteRoles { get; set; }
    }

 public partial class SiteAction
    {
        public SiteAction()
        {

            this.Childs = new HashSet<SiteAction>();
            this.SiteRoles = new HashSet<SiteRole>();
        }

        public int Id { get; set; }
        public string Name { get; set; }
        public string ImagePath { get; set; }
        public string ActionName { get; set; }
        public string ControllerName { get; set; }
        public Nullable<int> ParentId { get; set; }
        public Nullable<int> Type { get; set; }


        public virtual ICollection<SiteAction> Childs { get; set; }
        public virtual SiteAction Parent { get; set; }
        public virtual ICollection<SiteRole> SiteRoles { get; set; }
    }

  protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<SiteUser>().HasMany<SiteRole>(r => r.SiteRoles).WithMany(u => u.SiteUser).Map(m =>
        {
            m.ToTable("SiteUserRoles");
            m.MapLeftKey("SiteUserId");
            m.MapRightKey("SiteRoleId");
        });

        modelBuilder.Entity<SiteRole>().HasMany<SiteAction>(r => r.SiteActions).WithMany(u => u.SiteRoles).Map(m =>
        {
            m.ToTable("SiteRoleActions");
            m.MapLeftKey("SiteRoleId");
            m.MapRightKey("SiteActionId");
        });



        modelBuilder.Conventions.Remove<IncludeMetadataConvention>();
    }

【问题讨论】：

标签： c# .net linq entity-framework entity-framework-4

【解决方案1】：

由于您没有 SiteUserRoles 和 SiteRoleActions 作为实体，而只是作为连接表（如果我没看错的话），您应该使用导航属性而不是连接。比如：

conext.SiteUsers.Where(su => su.id == 1
    && su.SiteRoles.SelectMany(sr => sr.SiteActions)
        .Any(sa => sa.ParentId == 189 )

（未检查语法）。

【讨论】：

【解决方案2】：

  var result=   (from su in SiteUsers
           join sur in SiteUserRoles
           on su.Id=sur.SiteUserId
           join sra in SiteRoleActions
           on sur.SiteRoleId = sra.SiteRoleId
           join sa in SiteActions
           on sra.SiteActionId=sa.Id
           where su.Id=1 and sa.ParentId=189
           select su).ToList();

希望这会有所帮助。结果将是 SiteUsers 类型的列表。

【讨论】：