How to write XML Data from DataSet problem?

[RATOWNIK tomek]

Here is my code:

DataSet ds = new DataSet();
ds.ReadXml(new StringReader("INPUT.XML"), XmlReadMode.InferSchema);
 
int oTableNumber = 2;
DataRow oRow = ds.Tables[oTableNumber].NewRow();
oRow[0] = 3;
oRow[1] = "event-id3";
ds.Tables[oTableNumber].Rows.Add(oRow);
 
XmlTextWriter xtw = new XmlTextWriter("OUTPUT.XML", Encoding.UTF8);
ds.WriteXml(xtw, XmlWriteMode.IgnoreSchema);
 

HERE is my INPUT.XML file

<?xml version="1.0" encoding="UTF-8"?>
<request date="1900-01-01" package="1" event-type="E03">
    <event-E03>
        <request-portout-list-element>
            <veryfication-type>1</veryfication-type>
            <event-id>event-id1</event-id>
        </request-portout-list-element>
        <request-portout-list-element>
            <veryfication-type>2</veryfication-type>
            <event-id>event-id2</event-id>
        </request-portout-list-element>
    </event-E03>
</request>
 
 

and here is the OUTPUT.XML ???

<request date="1900-01-01" package="1" event-type="E03">
    <event-E03>
        <request-portout-list-element>
            <veryfication-type>1</veryfication-type>
            <event-id>event-id1</event-id>
        </request-portout-list-element>
        <request-portout-list-element>
            <veryfication-type>2</veryfication-type>
            <event-id>event-id2</event-id>
        </request-portout-list-element>
    </event-E03>
</request>
<request-portout-list-element>
    <veryfication-type>3</veryfication-type>
    <event-id>event-id3</event-id>
</request-portout-list-element>
 

Why does the OUTPUT.XML look like this?
Look at the 'REQUEST-PORTOUT-LIST-ELEMENT' element at the bottom of the xml?