string sFile = filename_users;
StreamWriter sw = new StreamWriter(sFile);
sw.WriteLine("<?xml version='1.0' standalone='yes'?>\r\n");
sw.WriteLine("<Client>\r\n");
sw.WriteLine("\t<xs:schema id='Client' xmlns=''" & _
  "xmlns:xs='http://www.w3.org/2001/XMLSchema'" & _
  "xmlns:msdata='urn:schemas-microsoft-com:xml-msdata'>\r\n");
sw.WriteLine("\t\t<xs:element name='Client' msdata:IsDataSet='true'" & _
"msdata:Locale='en-US'>\r\n");
sw.WriteLine("\t\t\t<xs:complexType>\r\n");
sw.WriteLine("\t\t\t\t<xs:choice minOccurs='0' maxOccurs='unbounded'>\r\n");
sw.WriteLine("\t\t\t\t\t<xs:element name='allow'>\r\n");
sw.WriteLine("\t\t\t\t\t\t<xs:complexType>\r\n");
sw.WriteLine("\t\t\t\t\t\t\t<xs:sequence>\r\n");
sw.WriteLine("\t\t\t\t\t\t\t\t\t<xs:element name='id' type='xs:string'" & _
  "default='2' minOccurs='0' />\r\n");
sw.WriteLine("\t\t\t\t\t\t\t\t\t<xs:element name='ip' type='xs:string'" & _
"minOccurs='0' />\r\n");
sw.WriteLine("\t\t\t\t\t\t\t\t\t<xs:element name='authorizations'" & _
"type='xs:boolean' minOccurs='0' />\r\n");
sw.WriteLine("\t\t\t\t\t\t\t</xs:sequence>\r\n");
sw.WriteLine("\t\t\t\t\t\t</xs:complexType>\r\n");
sw.WriteLine("\t\t\t\t\t</xs:element>\r\n");
sw.WriteLine("\t\t\t\t</xs:choice>\r\n");
sw.WriteLine("\t\t\t</xs:complexType>\r\n");
sw.WriteLine("\t\t</xs:element>\r\n");
sw.WriteLine("\t</xs:schema>\r\n");
sw.WriteLine("\t<allow>\r\n");
sw.WriteLine("\t\t<id>0</id>\r\n");
sw.WriteLine("\t\t<ip>127.0.0.1</ip>\r\n");
sw.WriteLine("\t\t<authorizations>false</authorizations>\r\n");
sw.WriteLine("\t</allow>\r\n");
sw.WriteLine("</Client>\r\n");
sw.Close();

ein bug im Programm wird immer als v1.0 bezeichnet