ISessionManager sessionManager = new SessionManagerClient();
API_SessionService.LogonRequest logonRequest = new API_SessionService.LogonRequest();
String username = "jsmith";  String password = "P@ssword2";
String domain  = "def";
logonRequest.logonRequestData = new LogonRequestData();
logonRequest.logonRequestData.DomainCode = domain;
logonRequest.logonRequestData.AgentName = userName;
logonRequest.logonRequestData.Password = password;
API_SessionService.LogonResponse logonResponse =

sessionManager.Logon(logonRequest);
if (logonResponse != null && logonResponse.Signature != null && logonResponse.Signature !=
  string.Empty)
{
//Completed Logon, you can now use the signature to call the API

string _signature = logonResponse.Signature;

}