创建DataSet和DataTable

 DataSet dataSet = new DataSet("dataSet");
        dataSet.Namespace = "NetFrameWork";
        DataTable table = new DataTable();
        DataColumn idColumn = new DataColumn("id", typeof(int));
        idColumn.AutoIncrement = true;

        DataColumn itemColumn = new DataColumn("item");
        table.Columns.Add(idColumn);
        table.Columns.Add(itemColumn);
        dataSet.Tables.Add(table);

        for (int i = 0; i < 2; i++)
        {
            DataRow newRow = table.NewRow();
            newRow["item"] = "item " + i;
            table.Rows.Add(newRow);
        }

        dataSet.AcceptChanges();

        string json = JsonConvert.SerializeObject(dataSet, Formatting.Indented);