Why does Textbox highlight text?

anyone know why when setting the text value of a textbox in runtime it highlights the text in the textbox?

i dont get the highlighting problem , but i know that if you set the SelectionStart to the length of text it should prevent it being highlighted , eg:

VB Code:

textBox1.AppendText("some text");
textBox1.SelectionStart = textBox1.Text.Length;

This property should be on .

Code:

---

textBox1.HideSelection=true;

---