asp.net simple single sign-on technology analysis

The code is as follows:
Copy Code code as follows:
Single sign-on (Sign on)
public void Ssomethods (string username, string password)
{
Judge the login situation here the method omits ...
int result = Checklogin (username, password);
if (result>0)
{
Unique identification, can be set by itself
String key = String. Format ("{0}_{1}", username, password);
Get the key value in cache
String usercache = Cache[key]. ToString ();
To determine if it is empty
if (string. IsNullOrEmpty (Usercache))
{
TimeSpan sessiontimeout = new TimeSpan (0,0,httpcontext.current.session.timeout,0,0);
HttpContext.Current.Cache.Insert (Key,key,null,datetime.maxvalue,sessiontimeout,cacheitempriority,notremovable, NULL);
session["User"] = key;
Response.Write ("<font color=red> login successful!) </font> ");
}
Else
{
Repsonse.write ("<font color=red> Sorry, you have already logged in elsewhere!" </font> ");
Return
}
}
Else
{
Response.Write ("User name does not exist!") ");
}
}