带有 poco 生成的实体框架 IQueryable

我创建了一个 T4 模板，它生成标准实体类及其每个属性的接口，以便我可以制作仅包含我想要的数据的自定义 poco 对象。我还创建了一个复制函数，它可以在实现所述实体接口的任何对象之间进行转换

生成的代码如下所示

//------------------------------------------------------------------------------
// <auto-generated>
//    This code was generated from a template.
//
//    Manual changes to this file may cause unexpected behavior in your application.
//    Manual changes to this file will be overwritten if the code is regenerated.
// </auto-generated>
//------------------------------------------------------------------------------

namespace DomainModel
{
    using System;
    using System.Collections.Generic;
    using System.Linq;


    public interface IRole
    {
    }
    public interface IRole_RoleId : IRole
    {
      int RoleId { get; set; }
    }
    public interface IRole_ApplicationName : IRole
    {
      string ApplicationName { get; set; }
    }
    public interface IRole_RoleName : IRole
    {
      string RoleName { get; set; }
    }
    public interface IRole_Description : IRole
    {
      string Description { get; set; }
    }

    public interface IRole_Users : IRole 
    {
      ICollection<IUser> Users { get; set; }
      IUser NewUsers();
    }

    public interface IRole__All : IRole_RoleId, 
      IRole_ApplicationName, 
      IRole_RoleName, 
      IRole_Description, 
      IRole_Users
    {
    }

    public partial class Role : IRole
    {
      public Role()
      {
        this.Users = new HashSet<User>();
      }

      public int RoleId { get; set; }
      public string ApplicationName { get; set; }
      public string RoleName { get; set; }
      public string Description { get; set; }

      public virtual ICollection<User> Users { get; set; }
    }

    public static class IRoleExt
    {
      public static T CopyTo<T>(this IRole src , T dest = null  )  where T : class, IRole, new()
      {
        dest = dest ?? new T();
        dest.Copy(src);
        return dest;
      }
      public static void Copy(this IRole dest, IRole src)
      {
        var ms = new MergeStack();
        Role role;
        if((role = dest as Role) != null){
          ms.TryCopy<IRole,Role>((indexCopy) => {return indexCopy(role);}, src);
        }
        else if ((role = src as Role) != null){
          ms.TryCopy<Role,IRole>((indexCopy) => {return indexCopy(dest);}, role);
        }
        else{
          ms.TryCopy<IRole,IRole>((indexCopy) => {return indexCopy(dest);}, src);
        }
        dest.Copy(src, ms);
      }

      internal static void Copy(this IRole dest,
        IRole src,
        MergeStack ms)
      {
        dest.Set_RoleId(src.Get_RoleId());
        dest.Set_ApplicationName(src.Get_ApplicationName());
        dest.Set_RoleName(src.Get_RoleName());
        dest.Set_Description(src.Get_Description());
        dest.Set_Users(src.Get_Users(),ms);
      }
        public static Nullable<int> Get_RoleId(this IRole src)
      {
        IRole_RoleId srcIRole_RoleId;
        if((srcIRole_RoleId = src as IRole_RoleId) != null )
        {
          return srcIRole_RoleId.RoleId;
        }
        Role role;
        if((role = src as Role) != null )
        {
          return role.RoleId;
        }
          return null;

      }
        public static void Set_RoleId(this IRole dest, Nullable<int> src)
      {
        IRole_RoleId destIRole_RoleId;
        if((destIRole_RoleId = dest as IRole_RoleId) != null)
        {
           destIRole_RoleId.RoleId = src.GetValueOrDefault();
            }
        Role role;
        if((role = dest as Role) != null )
        {
          role.RoleId = src.GetValueOrDefault();
        }
      }

        public static string Get_ApplicationName(this IRole src)
      {
        IRole_ApplicationName srcIRole_ApplicationName;
        if((srcIRole_ApplicationName = src as IRole_ApplicationName) != null )
        {
          return srcIRole_ApplicationName.ApplicationName;
        }
        Role role;
        if((role = src as Role) != null )
        {
          return role.ApplicationName;
        }
          return null;

      }
        public static void Set_ApplicationName(this IRole dest, string src)
      {
        IRole_ApplicationName destIRole_ApplicationName;
        if((destIRole_ApplicationName = dest as IRole_ApplicationName) != null)
        {
           destIRole_ApplicationName.ApplicationName = src;
            }
        Role role;
        if((role = dest as Role) != null )
        {
          role.ApplicationName = src;
        }
      }

        public static string Get_RoleName(this IRole src)
      {
        IRole_RoleName srcIRole_RoleName;
        if((srcIRole_RoleName = src as IRole_RoleName) != null )
        {
          return srcIRole_RoleName.RoleName;
        }
        Role role;
        if((role = src as Role) != null )
        {
          return role.RoleName;
        }
          return null;

      }
        public static void Set_RoleName(this IRole dest, string src)
      {
        IRole_RoleName destIRole_RoleName;
        if((destIRole_RoleName = dest as IRole_RoleName) != null)
        {
           destIRole_RoleName.RoleName = src;
            }
        Role role;
        if((role = dest as Role) != null )
        {
          role.RoleName = src;
        }
      }

        public static string Get_Description(this IRole src)
      {
        IRole_Description srcIRole_Description;
        if((srcIRole_Description = src as IRole_Description) != null )
        {
          return srcIRole_Description.Description;
        }
        Role role;
        if((role = src as Role) != null )
        {
          return role.Description;
        }
          return null;

      }
        public static void Set_Description(this IRole dest, string src)
      {
        IRole_Description destIRole_Description;
        if((destIRole_Description = dest as IRole_Description) != null)
        {
           destIRole_Description.Description = src;
            }
        Role role;
        if((role = dest as Role) != null )
        {
          role.Description = src;
        }
      }

      public static ICollection<IUser> Get_Users(this Role src)
      {
        return src.Users.Cast<IUser>().ToList();
        }
        public static ICollection<IUser> Get_Users(this IRole src)
      {
        IRole_Users srcIRole_Users;
        if((srcIRole_Users = src as IRole_Users) != null )
        {
          return srcIRole_Users.Users;
        }
        Role role;
        if((role = src as Role) != null )
        {
          return role.Get_Users();
        }
          return null;
      }
      public static void Set_Users(this IRole dest, ICollection<IUser> src)
      {
        var ms = new MergeStack();
        dest.Set_Users(src, ms);
      }

      internal static void Set_Users(this IRole dest, ICollection<IUser> src, MergeStack ms)
      {
        IRole_Users destIRole_Users;
        if((destIRole_Users = dest as IRole_Users) != null)
        {
          Func<IUser,IUser> iToIFunc = (x=> 
              ms.TryCopy<IUser,IUser>((indexCopy)=>
              {
                var ret = destIRole_Users.NewUsers();
                  var exists = indexCopy(ret);
                if(null != exists)
                    ret = exists;
                  else
                  ret.Copy(x,ms);
                return ret;
              },x));
          destIRole_Users.Users = (null !=src)?
          src.Select(iToIFunc).ToList():null;
        }

        Role role;
        if((role = dest as Role) != null)
        {
          Func<IUser,User> iToEFunc = (x=> 
              ms.TryCopy<IUser,User>((indexCopy)=>
              {
                var ret = new User();
                  var exists = indexCopy(ret);
                if(null != exists)
                    ret = exists;
                  else
                  ret.Copy(x,ms);
                return ret;
              },x));
          role.Users = (null !=src)?
          src.Select(iToEFunc).ToList():null;
        }
      }
    }
}

您看到的合并堆栈对象是一个跟踪器，因此我可以处理引用循环。看起来像这样

using System;
using System.Collections.Generic;
using System.Linq;

namespace DomainModel
{

    internal class MergeStack
    {
        private readonly Dictionary<Type, Dictionary<Object, Object>> _mergeObjDict = new Dictionary<Type, Dictionary<object, object>>();
        private readonly IList<Action> _registerActions = new List<Action>();

        public T TryCopy<TKey, T>(Func<Func<T, T>, T> func, TKey key) where T : class
        {
            if (key == null)
                return null;

            Func<T, T> act = (objToIndex) =>
            {
                Dictionary<object, object> objToObj;
                if (!_mergeObjDict.ContainsKey(objToIndex.GetType()))
                {
                    objToObj = new Dictionary<object, object>();
                    _mergeObjDict.Add(objToIndex.GetType(), objToObj);
                }
                else
                {
                    objToObj = _mergeObjDict[objToIndex.GetType()];
                }
                if (!objToObj.ContainsKey(key))
                {
                    objToObj.Add(key, objToIndex);
                }
                else
                {
                    return objToObj[key] as T;
                }
                return null as T;
            };
            return func(act);
        }
    }
}

现在，所有这些都按预期工作正常，它成功地将所有实现的属性复制到域模型/接口或从域模型/接口复制。

我现在正在尝试使用 IQueryable 和延迟加载来玩得更好。

现在我正在做这个

dbContext.Roles.Select((x)=> x.CopyTo<RolesPoco>());

我想看看是否有一种方法可以自动生成包含内容，例如

dbContext.Roles.Select((x)=> x.Users.Include((y)=> y.someSubEntity);

我还想看看是否可以添加一些像这样的 where 子句

//the first string is a path so something like "Roles.Users.someSubEntity"
//the second string is a IQueryable function like Where or Take
Dictionary<String,Dictionary<String,List<Func<T, IQueryable<TProperty>>>> queryDict

dbContext.Roles.Select((x)=> x.CopyTo<RolesPoco>(queryDict)

然后列表将是一些可以在包含函数内部运行的 lambda 列表。 有人对此有什么想法吗？

Edit：我重构简化了一些代码，以便即使该类没有实现该接口，它也可以调用 getter/setter。因此，无论是否存在支持字段，都可以访问属性。如果未定义则返回 null。

Edit2: 由于似乎不清楚我想要实现什么，让我澄清一下。如果你继续阅读本文的备注部分msdn页面 http://msdn.microsoft.com/en-us/library/gg671236%28v=vs.103%29.aspx，你会看到一些选择语句。我想生成这些表达式，然后根据要复制到的类是否包含实现该成员的接口在父选择内部使用它们。我避免使用 linqToObject，因为我只需要 CopyTo 中定义的属性，但导航属性是接口，这会破坏实体框架。这是为了延迟加载的目的。 MergeStack 将在树上组合并返回这些表达式。我的想法来自DaedTech 博客文章 http://www.daedtech.com/faking-an-interface-mapping-in-entity-framework

Roles 是 IQueryable 的，因此您需要从 Queryable 扩展类中获取 Select 方法。 您还需要从 Enumerable 扩展类中获取 Include。 然后，您需要使用 Role 作为通用参数来调用 Select 方法。 您需要使用 Expression.Lambda、Expression.Call 和 Expression.Property 构造 lambda。