Question

I am trying to output a XML file by fetching data from a dataset. However, the xml file is always empty. Could you please help me to find the error in my code?

class Program
{
    static void Main(string[] args)
    {
        string umail = "";
        XDocument loaded = XDocument.Load(@"C:\1.xml");

        var q = from c in loaded.Descendants("AdminUserDB.dbo.U_User")
                select (string)c.Element("URI");

        foreach (string em in q)
            umail = em;

        SqlConnection cn = new SqlConnection("server=(local);database=AdminUserDB;Persist Security Info=True; uid=sa;pwd=P@swrd123");
        cn.Open();

        DataSet ds = new DataSet();

        SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM dbo.U_User WHERE URI=@umail", cn);

        da.SelectCommand.Parameters.AddWithValue("@umail", umail);

        da.Fill(ds);

        string filename = "output.xml";

        System.IO.FileStream myFileStream = new System.IO.FileStream(filename, System.IO.FileMode.Create);

        System.Xml.XmlTextWriter myXmlWriter = new System.Xml.XmlTextWriter(myFileStream, System.Text.Encoding.Unicode);

        ds.WriteXml(myXmlWriter);

        myXmlWriter.Close();

        cn.Close();

    }
}

}

I am also trying to use DataSet.WriteXml method directly, however, I could not find which namespace should be referenced. I searched for WriteXml on MSDN, but I could not find the System.Data.DataSet namespace, which is listed on the WriteXml method page.

Thanks

SuT

Answer 1

Your code is leaking resources, always dispose disposable objects immediately. Otherwise you’ll be leaving files locked, and consume resources. Close doesn’t call Dispose.

DataSet ds = new DataSet();

using(SqlConnection cn = new SqlConnection("server=(local);database=AdminUserDB;Persist Security Info=True; uid=sa;pwd=P@swrd123"))
{
    cn.Open();

    using(SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM dbo.U_User WHERE URI=@umail", cn))
    {
        da.SelectCommand.Parameters.AddWithValue("@umail", umail);
        da.Fill(ds);
    }
}

string filename = "output.xml";

using(FileStream myFileStream = new FileStream(filename, FileMode.Create))
{
    using(XmlTextWriter myXmlWriter = new XmlTextWriter(myFileStream, Encoding.Unicode))
    {
        ds.WriteXml(myXmlWriter);
    }
}

If after calling dispose on your streams you still don’t see anything there’s prob no data.