there is an error in xml document (2 2) xmlns='' was not expected

The error I am getting is all over stackoverflow answered again and again, I have tried few changes in the code but not able to remove the error. here is the class I am using for serialization and deserialization. Please have a look at it.

I don't understand terms like XMLroot, XML element and namespace. So please answer accordingly, like what namespace should I give, what could be the XML root.

If u can edit it, it would be great:

namespace tudumo9
{

  public class data
  {
    public string project_name;
    public string note_text;
    public string tag_text;
    public DateTime start_date;
    public DateTime due_date;
    public string action;

    public  data(){}

  }
}

My XML:

<?xml version="1.0"?>
<ArrayOfData xmlns:xsi="http://ift.tt/ra1lAU" 
             xmlns:xsd="http://ift.tt/tphNwY">
  <data>
    <project_name>p1</project_name>
    <tag_text>tagged</tag_text>
    <start_date>0001-01-01T00:00:00</start_date>
    <due_date>0001-01-01T00:00:00</due_date>
    <action>Action</action>
  </data>
</ArrayOfData>