[c#] GUI questions

How can I update my user interface from a thread that did not create it?

TextBox m_textBox;
public delegate void UpdateTextCallback(string text);
void UpdateTextBox(strin i_text)
{
m_textBox = i_text;
}

m_TextBox.Invoke(new UpdateTextCallback(this.UpdateText), new object[]{”Text generated on non-UI thread.”});

See also, http://www.techinterviews.com/c-developer-interview-questions