Evento Control.Enter

privatevoid textBox1_Enter(object sender, System.EventArgs e)
{
    // If the TextBox contains text, change its foreground and background colors.if (textBox1.Text != String.Empty)
    {
        textBox1.ForeColor = Color.Red;
        textBox1.BackColor = Color.Black;
        // Move the selection pointer to the end of the text of the control.
        textBox1.Select(textBox1.Text.Length, 0);
    }
}

privatevoid textBox1_Leave(object sender, System.EventArgs e)
{
    // Reset the colors and selection of the TextBox after focus is lost.
    textBox1.ForeColor = Color.Black;
    textBox1.BackColor = Color.White;
    textBox1.Select(0,0);
}

private void textBox1_Enter(Object sender, System.EventArgs e)
{
    // If the TextBox contains text, change its foreground and background 
    // colors.
    if (!(textBox1.get_Text().Equals(""))) {
        textBox1.set_ForeColor(Color.get_Red());
        textBox1.set_BackColor(Color.get_Black());

        // Move the selection pointer to the end of the text of the 
        // control.
        textBox1.Select(textBox1.get_Text().get_Length(), 0);
    }
} //textBox1_Enter

private void textBox1_Leave(Object sender, System.EventArgs e)
{
    // Reset the colors and selection of the TextBox after focus is lost.
    textBox1.set_ForeColor(Color.get_Black());
    textBox1.set_BackColor(Color.get_White());
    textBox1.Select(0, 0);
} //textBox1_Leave