3 simbols all variables added in listbox

Here is permutation
private void button3_Click(object sender, EventArgs e)
{

listBox1.Items.Add("aaa");
listBox1.Items.Add("ccc");
listBox1.Items.Add("bbb");
char[] abc = new char[3]{'a','b','c'};
setper(abc);
char[] aab = new char[3] { 'a', 'a', 'b' };// you will need all char combinations eg aac,bba etc
setper(aab);
listBox1.Sorted = true;
//label1.Text = Convert.ToString(listBox1.Items.Count);
}

private void swap(ref char a, ref char b)
{
if (a == b)return;
a ^= b;
b ^= a;
a ^= b;
}

public void setper(char[] list)
{
int x = list.Length - 1;
go(list, 0, x);
}

private void go (char[] list, int k, int m)
{
int i;
if (k == m)
{
if (listBox1.Items.Contains(list[0].ToString() + list[1].ToString() + list[2].ToString()) == false)
{
listBox1.Items.Add(list[0].ToString() + list[1].ToString() + list[2].ToString());
}


}
else
for (i = k; i <= m; i++)
{
swap (ref list[k],ref list[i]);
go (list, k+1, m);
swap (ref list[k],ref list[i]);
}
}