from user in db.User order by Guid.NewID() select user　

 1 　　/// <summary>
 2     /// 數(shu)據(ju)上(shang)下文擴展
 3     /// </summary>
 4     public partial class dbDataContext
 5     {
 6         /// <summary>
 7         /// 隨機排序
 8         /// </summary>
 9         /// <returns></returns>
10         [Function(Name = "NewID", IsComposable = true)]
11         public Guid NewID()
12         {
13             return ((Guid)(this.ExecuteMethodCall(this, ((MethodInfo)(MethodInfo.GetCurrentMethod())))
　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　.ReturnValue));
14 
15         }
16     }

from user in db.User order by db.NewID() select user

1 List<string> productids={"1","2","3"};
2 linq.ToList().OrderByDescending(a => productids
3              .IndexOf(a.MC_ProductID))
4              .ToList();