隨著使用者輸入文字的多少，改變TextBox的形狀大小

private void textBox1_TextChanged(object sender, EventArgs e) {

 Size size = TextRenderer.MeasureText(textBox1.Text, textBox1.Font); 
 textBox1.Width = size.Width; textBox1.Height = size.Height; 

 }

參考
http://stackoverflow.com/questions/8048455/c-sharp-resize-textbox-to-fit-content