Why is connection closed after Command.ExecuteNonQuery()?

private static string connectionString = @"User Id=****;Password=****;Host=****;Database=****;Persist Security Info=True";

        public MySqlConnection Connection = null;
        public MySqlTransaction Transaction = null;
        private MySqlCommand Command = null;

        public LinqDataContext(string p_ConnectionString = "")
        {
            if (string.IsNullOrWhiteSpace(p_ConnectionString) == false)
            {
                connectionString = p_ConnectionString;
            }
            Connection = new MySqlConnection(connectionString);
        }

public int InsertPayee(System.Nullable<int> p_StoreID, System.Nullable<int> p_PayeeID, string p_PayeeName, string p_StreetAddress, string p_City, System.Nullable<int> p_StateID, string p_ZipCode, string p_PhoneNumber, string p_EmailAddress, string p_Notes, System.Nullable<int> p_CarrierID, System.Nullable<bool> p_IsActive, System.Nullable<int> p_RegisterID)
       {
           using (Connection)
           {
               if (Connection.State != ConnectionState.Open)
               {
                   Connection.Open();
               }

               Command = new MySqlCommand("InsertPayee", Connection);
               Command.CommandType = CommandType.StoredProcedure;
               if (Transaction != null)
               {
                   Command.Transaction = Transaction;
               }

               Command.Parameters.Add(new MySqlParameter("p_StoreID", p_StoreID));
               Command.Parameters.Add(new MySqlParameter("p_PayeeID", p_PayeeID));
               Command.Parameters.Add(new MySqlParameter("p_PayeeName", p_PayeeName));

               Command.Parameters.Add(new MySqlParameter("p_StreetAddress", p_StreetAddress));
               Command.Parameters.Add(new MySqlParameter("p_City", p_City));
               Command.Parameters.Add(new MySqlParameter("p_StateID", p_StateID));

               Command.Parameters.Add(new MySqlParameter("p_ZipCode", p_ZipCode));
               Command.Parameters.Add(new MySqlParameter("p_PhoneNumber", p_PhoneNumber));
               Command.Parameters.Add(new MySqlParameter("p_EmailAddress", p_EmailAddress));

               Command.Parameters.Add(new MySqlParameter("p_Notes", p_Notes));
               Command.Parameters.Add(new MySqlParameter("p_CarrierID", p_CarrierID));
               Command.Parameters.Add(new MySqlParameter("p_IsActive", p_IsActive));

               Command.Parameters.Add(new MySqlParameter("p_RegisterID", p_RegisterID));

               return Command.ExecuteNonQuery();
           }
       }