ASP.NET : Identify XSD on the basis of XML in Web Service

Question

Hi Experts,

My Web Service have set of Xsd's. Like V1.xsd, V2.xsd, V3.xsd. From client side, client will send V1.xml based on V1.xsd in web service or V2.xml based on V2.xsd or V3.xml based on V3.xsd How will decide which Xml passed from client side to Xsd present in Web Service.
eg : My Sample Xml from Client1 is :

<Sis>
  <Student>
    <StudentID>1</StudentID>
    <AcademicDetails>2008-2009</AcademicDetails>
    <PersonalDetails>
      <FirstName>Vijay</FirstName>
      <MiddleName>Laxmanrao</MiddleName>
      <LastName>Jadhav</LastName>
    </PersonalDetails>
  </Student>
</Sis>

How to determine Xsd for this in Web service ? Please help asap.
Note : I am using C#.Net (. Net FW 3.5) .
Thanks.