How to add name space to XML using C#

<?xml version="1.0" encoding="UTF-8"?>
<ns0:MT_SLM_softwareCostRate xmlns:ns0="urn:DPS:SoftwareCostRate:SLM_To_S4">
   <SLM_SoftwareDetails>
      <SW_Name>MS Visio</SW_Name>
      <SW_Licence_Type>Perpetual</SW_Licence_Type>
      <SW_Cost>100</SW_Cost>
      <Currency>USD</Currency>
      <Year>2020</Year>
      <Month>DEC</Month>
   </SLM_SoftwareDetails>
</ns0:MT_SLM_softwareCostRate>

ns0:

writer.WriteStartElement("MT_SLM_softwareCostRate");
               writer.WriteAttributeString("xmlns", "ns0", null, "urn:DPS:SoftwareCostRate:SLM_To_S4");
writer.WriteStartElement("SLM_SoftwareDetails");
                   writer.WriteElementString("SW_Name", "Test");
                   writer.WriteElementString("SW_Licence_Type", "Test"));
                   writer.WriteElementString("SW_Cost", "Test");
                   writer.WriteElementString("Currency", "Test");
                   writer.WriteElementString("Year", "Test");
                   writer.WriteElementString("Month", "Test");