c# - 从 web 服务返回列表<object>

Question

我正在使用 Chartjs 处理折线图，但我的网络服务出现错误。这是该服务的代码:

[WebMethod]
    public List<object> getProgram12Months(string usersessionid)
    {
        List<object> iData = new List<object>();
        List<string> labels = new List<string>();

        //First get distinct Month Name for select Year.
        string query1 = "SELECT DISTINCT TOP (100) PERCENT TimeFrame FROM dbo.CSQ_ProgramCount12Months ORDER BY TimeFrame ";

        string conn = ConfigurationManager.ConnectionStrings["LocalSqlServer"].ConnectionString;
        SqlDataAdapter dap = new SqlDataAdapter(query1, conn);
        DataSet ds = new DataSet();
        dap.Fill(ds);
        DataTable dtLabels = ds.Tables[0];


        foreach (DataRow drow in dtLabels.Rows)
        {
            labels.Add(drow["TimeFrame"].ToString());
        }
        iData.Add(labels);

        return iData;
    }

当我从浏览器调用该方法时，出现以下错误:

System.InvalidOperationException: There was an error generating the XML document. ---> System.InvalidOperationException: The type System.Collections.Generic.List`1[[System.String, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]] may not be used in this context.

我的基础是off this .

Answer 1

List 不可序列化为 Web 方法，您可以返回 object[]。

[WebMethod]
    public object[] getProgram12Months(string usersessionid)
    {
        List<object> iData = new List<object>();
        List<string> labels = new List<string>();

        //First get distinct Month Name for select Year.
        string query1 = "SELECT DISTINCT TOP (100) PERCENT TimeFrame FROM dbo.CSQ_ProgramCount12Months ORDER BY TimeFrame ";

        string conn = ConfigurationManager.ConnectionStrings["LocalSqlServer"].ConnectionString;
        SqlDataAdapter dap = new SqlDataAdapter(query1, conn);
        DataSet ds = new DataSet();
        dap.Fill(ds);
        DataTable dtLabels = ds.Tables[0];


        foreach (DataRow drow in dtLabels.Rows)
        {
            labels.Add(drow["TimeFrame"].ToString());
        }
        iData.Add(labels.ToArray());

        return iData.ToArray();
    }