webserver for TLS 1.1

Question

Hi,  application which will receive/sends order requests from XML customers and it is built on win 2003 OS (security protocal SSL3). It has 12 XML customerss out which 1 XML customer is upgrading their security protocal to TLS 1.1 from SSL3. So far the XML communication between two systems through SSL3. As we cannot upgrade the intrastructure to support TLS 1.1 need to build webservice in C#. so that, the new webservice will take the XML request from XML customer in the format of TLS1.1 and it should convert to SSL3. 

Please can you help me how to write web service for TLS 1.1. Thank you.