c# - 从方法返回数据读取器

Question

我有以下方法

    public static SqlDataReader MenuDataReader(string url)
    {
        using (SqlConnection con = new SqlConnection(connectionString))
        {
            using (SqlCommand cmd = new SqlCommand("spR_GetChildMenus", con))
            {
                cmd.CommandType = CommandType.StoredProcedure;
                cmd.Parameters.AddWithValue("@PageUrl", url);
                cmd.Parameters.AddWithValue("@MenuId", ParameterDirection.Output);
                cmd.Parameters.AddWithValue("@ParentId", ParameterDirection.Output);
                cmd.Parameters.AddWithValue("@TitleText", ParameterDirection.Output);
                cmd.Parameters.AddWithValue("@ExternalUrl", ParameterDirection.Output);
                cmd.Parameters.AddWithValue("@FullUrl", ParameterDirection.Output);
                cmd.Parameters.AddWithValue("@ChildCount", ParameterDirection.Output);
                con.Open();
                SqlDataReader reader = cmd.ExecuteReader();
                if (reader.HasRows)
                {
                    //return reader;

                    while (reader.Read())
                    {
                        return reader;
                    }

                }
            }
        }
        return null;
    }

我是这样调用的

        SqlDataReader reader = MenuDataReader(url);
        if (reader.HasRows)
        {
            while (reader.Read())
            { }}

但是我收到了错误信息

Invalid attempt to call HasRows when reader is closed.

谁能帮帮我

谢谢

Answer 1

如 https://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqlcommand(v=vs.110).aspx 所示:

  public static SqlDataReader ExecuteReader(String connectionString, String commandText,
      CommandType commandType, params SqlParameter[] parameters) {
     SqlConnection conn = new SqlConnection(connectionString);

     using (SqlCommand cmd = new SqlCommand(commandText, conn)) {
        cmd.CommandType = commandType;
        cmd.Parameters.AddRange(parameters);

        conn.Open();
        // When using CommandBehavior.CloseConnection, the connection will be closed when the 
        // IDataReader is closed.
        SqlDataReader reader = cmd.ExecuteReader(CommandBehavior.CloseConnection);

        return reader;
     }
  }