How to write my info on one line in listbox

Question

{ this.listBox1.Items.Add(IDtextbox.Text.ToString()); this.listBox1.Items.Add(LasttextBox.Text.ToString()); this.listBox1.Items.Add(FirsttextBox.Text.ToString()); } How would I get it to write these three all on the same line? Possibly put a comma between the last name and first. And a space between the ID and last name. thanks