Combinations values without repetition

hi, 
i want to display all the possible values of the string dinamically for eg i may have value in my data column as "ABC" 
i want to display combinations value like "A, B, C, AB , BC, AC, ABC"  how to diplay the values, i calucaled the total number of values to diplay by using the below loop
 
 for (int r = 1; r <= n; r++)
        {
            int factorialValue = (factorial(n) / (factorial(r) * factorial(n - r)));
            for (int k = 1; k <= factorialValue; k++)
            {
                //add the code to get the value
            }

...