How to sort multiple decimal numbers in a list

Question

I want to sort multi decimal numbers (1.1, 1.2, etc.). I have a set of numbers:

1.100
1
1.33
1.33.1
1.2
1.05
1.05.1.1

And I want it to become:

1
1.05
1.05.1.1
1.2
1.33
1.33.1
1.100

My code:

private void button1_Click(object sender, EventArgs e)
{
    act.Add("1.100");
    act.Add("1.1"); 
    act.Add("1.33");    
    act.Add("1.33.1"); 
    act.Add("1.2");   
    act.Add("1.05"); 
    act.Add("1.05.1.1");
    act.Sort();

    for (int i = 0; i < act.Count; i++)
    {
        richTextBox1.AppendText(act[i] + Environment.NewLine);
    }
}