sting.Equals(string a,string b)
 
Explanation:
 Determines whether two specified system.string objects have
the same values,a parameter specifies the culture,case and
sort rules used in the comparison

Here is the code that solve ur problem:

       string str = "virtual";
        if (str.Equals("virtual"))
        {
          // your code here....
        }

string str1="Hello1";
string str2="Hello2";

String.Compare(str1,str2,true)

//true if you want compare two string without case 
sensative and false if you want to case sensative.

//It will return Zero if compare as equal and 1 if not.

with
String.Compare(string a,string b)  [result 0 only when it 
is equal- since it compares by subtracting ascii of b from 
ascci of a)
or
String.Equals(string a,string b)  {true if it is equal] 
we can achieve the same

just write session["name"]=null;

session.abandont

using
session.abandon method

Session.RemoveAll();

by using session.kill()

by using session.abandon()
this cancels the current session immediately and releases 
all memory it occupied

session.abandon();

there are two ways to kill the session
1:abandon method
2:don't write anything in session it will automatically
kill

You can use 
Session.Abandon();
Or 
Session.RemoveAll();
or 
Session.Clear();

But it is better to use Session.Abandon()
because it will removes associated session is also

http://prajeeshkk.blogspot.com/
http://dotnetbird.wordpress.com/

There is nothing like Session.Kill in ASP.NET. So please 
update this. Best answer is Session.Abandon

We can use these to clear session
Session.Abandon();
this.sessio.clear();