如何从 .NET Web 服务返回 JSON 编码的数组？

Question

我已经使用 JSON 创建了一个 .NET Web 服务。但结果没有显示为数组。如何将 JSON 结果放入我的 Web 服务中的数组？

这是我的网络服务代码：

[WebMethod]
    [ScriptMethod(ResponseFormat = ResponseFormat.Json)]
    public String GetReport()
    {
        ModelReport.Report report = new ModelReport.Report();
        string connectionString = ConfigurationManager.ConnectionStrings["ConnWf"].ConnectionString;
        using (SqlConnection connection = new SqlConnection(connectionString))
        {
            string sql = "select type, sum(OrderQty) as total from tbl_weeklyflash_ID where type <> 'NULL' group by type";
            connection.Open();

            SqlCommand command = new SqlCommand(sql, connection);
            SqlDataReader reader = command.ExecuteReader();
            while (reader.Read())
            {
                report.type = reader["type"].ToString();
                report.total = reader["total"].ToString();
            }
        }

        MemoryStream stream = new MemoryStream();
        DataContractJsonSerializer serializer = new DataContractJsonSerializer(typeof(ModelReport.Report));
        serializer.WriteObject(stream, report);
        stream.Position = 0;
        StreamReader streamReader = new StreamReader(stream);
        return streamReader.ReadToEnd(); 
    }

Answer 1

您正在序列化 Report 对象的单个实例，而不是数组。所以第一步就是建一个数组：

[WebMethod]
[ScriptMethod(ResponseFormat = ResponseFormat.Json)]
public String GetReport()
{
    List<ModelReport.Report> reports = new List<ModelReport.Report>();
    string connectionString = ConfigurationManager.ConnectionStrings["ConnWf"].ConnectionString;
    using (SqlConnection connection = new SqlConnection(connectionString))
    {
        string sql = "select type, sum(OrderQty) as total from tbl_weeklyflash_ID where type <> 'NULL' group by type";
        connection.Open();

        SqlCommand command = new SqlCommand(sql, connection);
        SqlDataReader reader = command.ExecuteReader();
        while (reader.Read())
        {
            ModelReport.Report report = new ModelReport.Report();
            report.type = reader["type"].ToString();
            report.total = reader["total"].ToString();
            reports.Add(report);
        }
    }

    MemoryStream stream = new MemoryStream();
    DataContractJsonSerializer serializer = new DataContractJsonSerializer(typeof(ModelReport.Report[]));
    serializer.WriteObject(stream, reports.ToArray());
    stream.Position = 0;
    StreamReader streamReader = new StreamReader(stream);
    return streamReader.ReadToEnd(); 
}

当然，第二步是正确执行此操作，并删除您方法中的任何管道代码，并将其留给基础架构：

[WebMethod]
[ScriptMethod(ResponseFormat = ResponseFormat.Json)]
public ModelReport.Report[] GetReport()
{
    List<ModelReport.Report> reports = new List<ModelReport.Report>();
    string connectionString = ConfigurationManager.ConnectionStrings["ConnWf"].ConnectionString;
    using (SqlConnection connection = new SqlConnection(connectionString))
    using (SqlCommand command = connection.CreateCommand)
    {
        string sql = "select type, sum(OrderQty) as total from tbl_weeklyflash_ID where type <> 'NULL' group by type";
        connection.Open();

        command.CommandText = sql;
        using (SqlDataReader reader = command.ExecuteReader())
        {
            while (reader.Read())
            {
                ModelReport.Report report = new ModelReport.Report();
                report.type = reader["type"].ToString();
                report.total = reader["total"].ToString();
                reports.Add(report);
            }
        }
    }

    return reports.ToArray();
}

您还会注意到，在我的第二个示例中，处理 IDisposable 资源的正确方法是始终将它们包装在 using 语句中。