How to return a JSON-encoded array from a .NET web service?

Question

I've create a .NET web service with JSON. but the result didn't show as array. how to make the JSON result into array in my web service?

here is my web service code:

[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(); 
    }

Darin Dimitrov · Accepted Answer · 2012-06-21 07:56:15Z

You are serializing a single instance of the Report object, not an array. So the first step is to build an array:

[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(); 
}

and the second step of course is to do this properly and get rid of any plumbing code in your method and leave this to the infrastructure:

[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();
}

You will also notice in my second example that the proper way to dispose IDisposable resources is to always wrap them in using statements.

Now I get it, thank you very much for your explanation :) but, in your second example, the result didn't show as JSON variable and I want the result in JSON variable, so I use your first example. Thanks again @Darin

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