ErrorProvider example and solution to remove error icon

Refer to http://stackoverflow.com/questions/7936438/errorprovider-using-class

public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private readonly ErrorProvider errorProvider1 = new ErrorProvider();

        private void textBox1_TextChanged(object sender, EventArgs e)
        {
            string text = textBox1.Text;
            bool hasDigit = false;
            foreach (char letter in text)
            {
                if (char.IsDigit(letter))
                {
                    hasDigit = true;
                    break;
                }
            }

            // Call SetError or Clear on the ErrorProvider.
            if (!hasDigit)
            {
                errorProvider1.SetError(textBox1, "Needs to contain a digit");
            }
            else
            {
                Icon i =  errorProvider1.Icon;
                errorProvider1.SetError(textBox1, "");
                i = errorProvider1.Icon;
            }
        }
    }