public static Task<int> SaveDeThiAsync(EZCode.Model.DeThi deThi)
 {
     if (deThi.Id == 0)
     {
         return Database.database.InsertAsync(deThi);
     }
     else
     {
         return Database.database.UpdateAsync(deThi);
     }
 }
 public static Task<int> DeleteDeThiAsync(EZCode.Model.DeThi deThi)
 {
     return Database.database.DeleteAsync(deThi);
 }