public static int delete(string username)
 {
     try
     {
         Database db = new Database();
         string queryString = "DELETE FROM [dbo].[Users] WHERE [username] = @username";
         List<SqlParameter> atrs = new List<SqlParameter>()
         {
             new SqlParameter() {ParameterName = "@username",SqlDbType= SqlDbType.NVarChar,Value = username }
         };
         int result = db.execute(queryString, atrs);
         db.Disconnect();
         return result;
     }
     catch (Exception ex)
     {
         Console.WriteLine(ex.Message);
         return 0;
     }
 }
 public static int save(User user)
 {
     try
     {
         Database db = new Database();
         string queryString = "INSERT INTO [dbo].[Users]([username],[password],[create_at]) VALUES(@username,@password,GETDATE())";
         List<SqlParameter> atrs = new List<SqlParameter>()
         {
             new SqlParameter() {ParameterName = "@username",SqlDbType= SqlDbType.NVarChar,Value = user.Username },
             new SqlParameter() {ParameterName = "@password",SqlDbType= SqlDbType.NVarChar,Value = user.Password }
         };
         int result = db.execute(queryString, atrs);
         db.Disconnect();
         return result;
     }
     catch (Exception ex)
     {
         Console.WriteLine(ex.Message);
         return 0;
     }
 }
 public static int update(User user)
 {
     try
     {
         Database db = new Database();
         string queryString = "UPDATE [dbo].[Users] SET [password] = @password WHERE [username] = @username";
         List<SqlParameter> atrs = new List<SqlParameter>()
         {
             new SqlParameter() {ParameterName = "@username",SqlDbType= SqlDbType.NVarChar,Value = user.Username },
             new SqlParameter() {ParameterName = "@password",SqlDbType= SqlDbType.NVarChar,Value = user.Password }
         };
         int result = db.execute(queryString, atrs);
         db.Disconnect();
         return result;
     }catch(Exception ex)
     {
         Console.WriteLine(ex.Message);
         return 0;
     }
 }