Writing XML files in C#

The XmlTextWriter class includes number of methods to create xml document content very easily. Consider we need to create a xml file called Employee.xml with the below data,

<?xml version="1.0" encoding="utf-8"?>

<Employees>

  <Employee type="Permanent">

    <ID>100</ID>

    <FirstName>Satheesh</FirstName>

    <LastName>Babu</LastName>

    <Dept>IT</Dept>

  </Employee>

</Employees>

If you see the above xml content, you can visualize it as an xml document having xml elements (Employees, Employee) or nodes with attributes (Type) and values (Satheesh). Keeping this in mind, to create the above XML document programmatically using XmlTextWriter class we need to first call WriteStartDocument() to start the document creation which emits the xml declaration. Next, you can subsequently use WriteStartElement(), WriteAttributeString() method to construct the whole document. Remember, any xml nodes created should have the matching closing nodes. This is done by calling WriteEndElement() and WriteEndDocument() methods.

Refer the below code.

protected void Page_Load(object sender, EventArgs e)

    {

        XmlTextWriter xmlwriter = new XmlTextWriter(Server.MapPath("App_Data/Employee.xml"), Encoding.UTF8);

        xmlwriter.Formatting = Formatting.Indented;

        xmlwriter.WriteStartDocument();       

        xmlwriter.WriteStartElement("Employees");

        xmlwriter.WriteStartElement("Employee");

        xmlwriter.WriteAttributeString("type", "Permanent");

        xmlwriter.WriteElementString("ID", "100");

        xmlwriter.WriteElementString("FirstName", "Satheesh");

        xmlwriter.WriteElementString("LastName", "Babu");

        xmlwriter.WriteElementString("Dept", "IT");

        xmlwriter.WriteEndElement();

        xmlwriter.WriteEndElement();

        xmlwriter.WriteEndDocument();

        xmlwriter.Flush();

        xmlwriter.Close();

   }

Once executed, it will create an xml document called Employee.xml in your project App_Data folder. You need to include the System.Xml and System.Text namespace for the above code to work.

In the above example, we have created a very basic xml document using XmlTextWriter class. This class has many more useful methods which can be used. The below code creates an xml document from a DataTable manually including XML comments.

protected void Page_Load(object sender, EventArgs e)

    {

       XmlTextWriter xmlwriter = new XmlTextWriter(Server.MapPath("App_Data/Employee.xml"), Encoding.UTF8);

        xmlwriter.Formatting = Formatting.Indented;

        xmlwriter.WriteStartDocument();

        xmlwriter.WriteComment("Programmatically writing XML");

        xmlwriter.WriteStartElement("Employees");

//GetEmployees() method returns DataTable with data. Download the code attached to see it in action

        DataTable dt = GetEmployees();

        for (int i = 0; i < dt.Rows.Count; i++)

        {

            xmlwriter.WriteStartElement("Employee");

            xmlwriter.WriteAttributeString("type", dt.Rows[i]["Type"].ToString());

            xmlwriter.WriteElementString("ID", dt.Rows[i]["ID"].ToString());

            xmlwriter.WriteElementString("FirstName", dt.Rows[i]["FirstName"].ToString());

            xmlwriter.WriteElementString("LastName", dt.Rows[i]["LastName"].ToString());

            xmlwriter.WriteElementString("Dept", dt.Rows[i]["Dept"].ToString());

            xmlwriter.WriteEndElement();

        }

        xmlwriter.WriteEndElement();

        xmlwriter.WriteEndDocument();

        xmlwriter.Flush();

        xmlwriter.Close();

    }

OUTPUT

<?xml version="1.0" encoding="utf-8"?>

<!--Programmatically writing XML-->

<Employees>

  <Employee type="Permanent">

    <ID>100</ID>

    <FirstName>Satheesh</FirstName>

    <LastName>&lt;b&gt;Babu</LastName>

    <Dept>IT</Dept>

  </Employee>

  <Employee type="Temporary">

    <ID>101</ID>

    <FirstName>Peters</FirstName>

    <LastName>Laurence</LastName>

    <Dept>Development</Dept>

  </Employee>

  <Employee type="Permamnet">

    <ID>102</ID>

    <FirstName>Rick</FirstName>

    <LastName>Anderson</LastName>

    <Dept>Sales</Dept>

  </Employee>

  <Employee type="Temporary">

    <ID>103</ID>

    <FirstName>Ramesh</FirstName>

    <LastName>Kumar</LastName>

    <Dept>HR</Dept>

  </Employee>

</Employees>

You can see the comments added in the above xml document.

Reading XML files in C#

Like XmlTextWriter class, the System.Xml namespace includes XmlTextReader class which can be used to read xml document. The below code reads all the text nodes from the Employee.xml file.

protected void Page_Load(object sender, EventArgs e)

    {

        using (XmlTextReader reader = new XmlTextReader(Server.MapPath("App_Data/Employee.xml")))

        {

            while (reader.Read())

            {

                if (reader.NodeType == XmlNodeType.Text)

                {

                    Response.Write(reader.Value);

                    Response.Write("<br>");

                }

            }

        }

    }

You can also read xml using xpath expressions. Refer the below article on codedigest.com which talks about reading xml document using xpath expressions.

Reading XML files in ASP.Net Using XPath