ADO.NET中LINQ查询问题

Question

 //查询所有的可以访问的相册
            var fal = fa.facelook_album
                .Where(a => a.USER_ID == UID || a.ALBUM_LIMIT == 1)
              //.Select(a => a);
                .Select(a => new { a, Cout = fa.facelook_photo.Where(p => p.ALBUM_ID == a.ALBUM_ID).Count() });
            //在集合后面添加一个集合
           
            //查询所有好友中授权的相册
            for (int i = 0; i < friendid.Length; i++)
            {
                var friid = friendid[i];
                //根据好友授权查询
                var fu = fa.facelook_album
                    .Where(al => al.USER_ID == friid && al.ALBUM_LIMIT == 2)
                    .Select(al => new { al, Cout = fa.facelook_photo.Where(p => p.ALBUM_ID == al.ALBUM_ID).Count() });
                    //.Select(al => al);
               fal= fal.Concat(fu);
            }
            
            return fal;如果我要Select(al => new { al, Cout = fa.facelook_photo.Where(p => p.ALBUM_ID == al.ALBUM_ID).Count() })这样查询的结果让两个查询结果连接成一张表要怎么做 fal= fal.Concat(fu);这样连接会报错

Answer 1

这种方法可以用不过查询的结果要给他这样写
 .Select(a => new
                    {
                        a.ALBUM_ID
                        ,
                        a.ALBUM_LIMIT
                        ,
                        a.ALBUM_NAME
                        ,
                        a.ALBUM_FILE_NAME
                        ,
                        a.ALBUM_DESC
                        ,
                        a.USER_ID
                        ,Cout = fa.facelook_photo.Where(p => p.ALBUM_ID == a.ALBUM_ID).Count()
                    });

Answer 2

看来你没见过SelectMany。那是不需要写for循环的。

Answer 3

我知道SelctMany这个方法可使好像我这里用不上 public IQueryable<facelook_album> AlbumAsFriend(string UID,string[] friendid)
        {
            //查询所有的可以访问的相册
            var fal = fa.facelook_album
                .Where(a => a.USER_ID == UID || a.ALBUM_LIMIT == 1)
              .Select(a => a);
                //.Select(a => new 
                //{ a.ALBUM_ID
                //    ,a.ALBUM_LIMIT
                //    ,a.ALBUM_NAME
                //    ,a.ALBUM_FILE_NAME
                //    ,a.ALBUM_DESC
                //    ,a.USER_ID
                //    , Cout = fa.facelook_photo.Where(p => p.ALBUM_ID == a.ALBUM_ID).Count()
                //});
            //在集合后面添加一个集合
            
            
            //查询所有好友中授权的相册
            for (int i = 0; i < friendid.Length; i++)
            {
                var friid = friendid[i];
                //根据好友授权查询
                var fu = fa.facelook_album
                    .Where(al => al.USER_ID == friid && al.ALBUM_LIMIT == 2)
                    //.Select(a => new
                    //{
                    //    a.ALBUM_ID
                    //    ,
                    //    a.ALBUM_LIMIT
                    //    ,
                    //    a.ALBUM_NAME
                    //    ,
                    //    a.ALBUM_FILE_NAME
                    //    ,
                    //    a.ALBUM_DESC
                    //    ,
                    //    a.USER_ID
                    //    ,Cout = fa.facelook_photo.Where(p => p.ALBUM_ID == a.ALBUM_ID).Count()
                    //});
                    .Select(a => a);
                //fal.ToList().AddRange(fu.ToList());
                fal = fal.Concat(fu);
            }
            
            return fal;
        }这里是多表关系查询返回一个数组 facelookEntities fa = new facelookEntities();
        public string[] SelectFriend(string UID)
        {
            int i = 0;
            string[] friend = new string[10];
            var fu = fa.facelook_user.First(u => u.USER_ID.Equals(UID));
            foreach (var item in fu.facelook_user1)
            {
                friend[i] = item.USER_ID;
                i++;
            }
            foreach (var item in fu.facelook_user2)
            {
                
                friend[i] = item.USER_ID;
                i++;
            }
            return friend;
        }