public string AddMsgbyRole(string roleID, string title, string message, string url)
 {
     string ret = "false";
     try
     {
         var qryU = db.UserData.Where(x => x.RoleID == roleID);
         foreach (UserData u in qryU)
         {
             if(u.EndDate.CompareTo(DateTime.Now) > 0){
                 var qryD = db.UserDevice.Where(x => x.UserID == u.UserID);
                 foreach (UserDevice d in qryD)
                 {
                     //int mID = db.MessageBox.AsEnumerable().Select(x => x.MessageID).DefaultIfEmpty(0).Max(x => x) + 1;
                     MessageBox messageBox = new MessageBox();
                     //messageBox.MessageID = mID;
                     messageBox.DeviceID = d.DeviceID;
                     messageBox.Title = title;
                     messageBox.MessageConten =u.UserName + message;
                     messageBox.URL = url;
                     messageBox.WriteDT = DateTime.Now;
                     db.MessageBox.Add(messageBox);
                     //db.SaveChanges();
                 }   
             }
         }
         db.SaveChanges();
         ret = "true";
     }
     catch 
     {
     }
     return ret;
 }
 public string AddMsgbyUser(string userID, string title, string message, string url)
 {
     string ret = "false";
     try
     {
         var qryD = db.UserDevice.Where(x => x.UserID == userID);
         foreach (UserDevice d in qryD)
         {                 
             MessageBox messageBox = new MessageBox();                 
             messageBox.DeviceID = d.DeviceID;
             messageBox.Title = title;
             messageBox.MessageConten = message;
             messageBox.URL = url;
             messageBox.WriteDT = DateTime.Now;
             db.MessageBox.Add(messageBox);
         }
         db.SaveChanges();
         ret = "true";
     }
     catch
     {
     }
     return ret;
 }