Convert Binary Code String to Hexadecimal

Possible duplicate:
Convert long string of binary code to hexadecimal C #

nyI'm is looking for a way to convert a binary string to a sixth string.

the binary string has four positions. the binary string looks something like this:

string binarystring= "1011";

      

        
        
        
      

    

the output line should look something like this:

output string="B";

      

        
        
        
      

    

Is there a way to convert a binary string to hex?