如何让我写的Xml文件第一行

如何让我写的Xml文件第一行

变成我想要的

？
代码如下：
// Create xml file.
System.Windows.Forms.SaveFileDialog saveFileDialog = new SaveFileDialog();
saveFileDialog.FileName = "testaa";

if( saveFileDialog.ShowDialog() == DialogResult.OK )
{
this.Cursor = Cursors.WaitCursor;

string path = saveFileDialog.FileName + ".xml";

XmlTextWriter writer = new XmlTextWriter( path, System.Text.Encoding.GetEncoding( "GB2312"));
writer.WriteStartDocument();
writer.WriteStartElement( "Entity" );

writer.WriteEndElement();
writer.WriteEndDocument();

writer.Close();
}
---------------------------------------------------------------

XmlTextWriter writer = new XmlTextWriter( path, System.Text.Encoding.UTF8);