writexml appends new and existing data to file

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VS2008

C#

Visual-Studio

I've tried online help and Goggle and I can't find any answer to this. When I call dataset.WritXML(string filename) after creating a new "Project" row my program appears to write all the existing rows then the new row and then repeats all the existing rows again. I've tried deleting the XML file after starting the program and before saving to see if it was just appending the data to the existing file but I still get the same output. I've looked at the dataset value when debugging and they look fine, no repeated rows.

I think there might be a problem with my schema file:

<?xml version="1.0" encoding="utf-8"?>
<xs:schema id="ProjectCommander" xmlns="" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:msdata="urn:schemas-microsoft-com:xml-msdata">
  <xs:element name="ProjectCommander" msdata:IsDataSet="true" msdata:UseCurrentLocale="true">
    <xs:complexType>
      <xs:choice minOccurs="0" maxOccurs="unbounded">
        <xs:element name="Project">
          <xs:complexType>
            <xs:sequence>
              <xs:element name="LastChangeNotice" type="xs:string" minOccurs="0" msdata:Ordinal="0" />
              <xs:element name="LastSiteInstruction" type="xs:string" minOccurs="0" msdata:Ordinal="1" />
              <xs:element name="MilestoneItem" minOccurs="0" maxOccurs="unbounded">
                <xs:complexType>
                  <xs:sequence>
                    <xs:element name="Date" type="xs:string" minOccurs="0" />
                    <xs:element name="Event" type="xs:string" minOccurs="0" />
                  </xs:sequence>
                </xs:complexType>
              </xs:element>
              <xs:element name="CommentItem" minOccurs="0" maxOccurs="unbounded">
                <xs:complexType>
                  <xs:sequence>
                    <xs:element name="Date" type="xs:string" minOccurs="0" />
                    <xs:element name="Description" type="xs:string" minOccurs="0" />
                  </xs:sequence>
                </xs:complexType>
              </xs:element>
            </xs:sequence>
            <xs:attribute name="ProjectID" type="xs:string" />
          </xs:complexType>
        </xs:element>
      </xs:choice>
    </xs:complexType>
  </xs:element>
</xs:schema>

Can anyone see anything wrong?