EF外连接 表达树

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Linq.Expressions;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {

            var s = new [] {
                        new {id=1 , name =2}, new {id=2, name =2},new {id=4, name =4}
                    };

            var d = new[] {
                        new {id=1 , make =2}, new {id=3, make =2}
                    };

            var b = new[] {
                        new {id=1 , code =2}, new {id=3, code =3},new {id=4, code =4}                                
                            };

            var q = from s1 in s
                    from b1 in b
                    where s1.id == b1.id
                    join d1 in d on s1.id equals d1.make where d1.id > 0
                    into sbs
                    from qq in sbs.DefaultIfEmpty()
                    select new
                    {
                        id = s1.id
                       num =   qq == null ? "": (string)qq.make
                    };
                    

            /*
            
            
              */



            /*
             
            
             
       
             
             
           var q = from s1 in s
                   from d1 in d
                   where s1.id == d1.id
                   select new
                   {
                       id = s1.id,
                       make =d1.make
                   };
            
           
           var q = from s1 in s
                   join d1 in d on s1.id equals d1.id
                   into ss
                   from p in ss.DefaultIfEmpty()
                   select new
                   {
                   id=s1.id,
                   make=  p == null ? 0 : p.make
                   };
           */



            foreach (var r in q)
            {
                Console.WriteLine(r.id);
                Console.WriteLine(r.make);
                Console.WriteLine("-------------");
            }
             


            /*
            ParameterExpression c = Expression.Parameter(typeof(aproduct), "aproduct");

            Expression condition = Expression.Constant(true);


          Expression con = Expression.Call(Expression.Property(c, typeof(aproduct).GetProperty("ProductId")),
                                                 typeof(int).GetMethod("Equals", new Type[] { typeof(int) }),
                                                Expression.Constant(1));

            
            condition = Expression.And(con, condition);
 
           Expression<Func<aproduct,bool>> end =  Expression.Lambda<Func<aproduct,bool>>(condition,new  ParameterExpression

[]{c});

            var db = new skyEntities();

            var q = db.aproduct.Where(end);      
 
            foreach(var s in q)
            {            
                Console.WriteLine(s.ProductId);
            }

            */
            
        }
    }

 

}