public bool UpdateUserMaterial(UserMaterial instance)
 {
     try
     {
         var userMaterial = Db.UserMaterials.Find(instance.UserMaterialId);
         var type = instance.GetType();
         foreach(var info in type.GetProperties())
         {
             if(info.CanWrite)
             {
                 var value = info.GetValue(instance);
                 if(value != null)
                 {
                     info.SetValue(userMaterial, value, null);
                 }
             }
         }
         Db.SaveChanges();
         return true;
     }
     catch
     {
         return false;
     }
 }
 public bool CreateUserMaterial(UserMaterial instance)
 {
     try
     {
         if (instance.UserMaterialId != 0) return false;
         Db.UserMaterials.Add(instance);
         Db.SaveChanges();
         return true;
     }
     catch
     {
         return true;
     }
 }