Getting error while adding a new row to a XML file from a datgridview?

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C#

XML

DataGridView

Hi,
I have a datgridview whose values are filled at run-time when the user decides to add a row.The same values are also written to a XML file after it is added to the DataGridView.
But instead of adding data to the file, the previously added data also gets deleted from the XML file and the form also freezes without adding row in the datagridview.

My code for creating the xml file is :

private void createXML()
        {
            DataTable dt = new DataTable();
            foreach (DataGridViewColumn col in dataGridView1.Columns)
            {
                dt.Columns.Add(col.HeaderText);
            }
            foreach (DataGridViewRow row in dataGridView1.Rows)
            {
                DataRow dRow = dt.NewRow();
                foreach (DataGridViewCell cell in row.Cells)
                {
                    dRow[cell.ColumnIndex] = cell.Value;
                }
                dt.Rows.Add(dRow);
            }
            DataSet ds = new DataSet();
            ds.Tables.Add(dt);
            ds.WriteXml(@"D:/HostAdded.xml");
        }

Please help!!!
its urgent :)