Implement Overtype Mode in MaskedTextBox

The button "Insert" on the PC's keyboard can switch the input mode, insert and overtype. Here implement the mode "overtype" in MaskedTextBox.

private void Form1_Load(object sender, EventArgs e)
{
    maskedTextBox1.Mask = "00/00/0000";
    maskedTextBox1.Text = "12/21/3321";
}

private void maskedTextBox1_KeyUp(object sender, KeyEventArgs e)
{

    string character = e.KeyData.ToString();
    //if (e.KeyData == Keys.D0 || e.KeyData == Keys.D1 || e.KeyData == Keys.D2 || e.KeyData == Keys.D3 || e.KeyData == Keys.D4
    //    || e.KeyData == Keys.D5 || e.KeyData == Keys.D6 || e.KeyData == Keys.D7 || e.KeyData == Keys.D8 || e.KeyData == Keys.D9
    //    || e.KeyData == Keys.NumPad0 || e.KeyData == Keys.NumPad1 || e.KeyData == Keys.NumPad2 || e.KeyData == Keys.NumPad3
    //    || e.KeyData == Keys.NumPad4 || e.KeyData == Keys.NumPad5 || e.KeyData == Keys.NumPad6 || e.KeyData == Keys.NumPad7
    //    || e.KeyData == Keys.NumPad8 || e.KeyData == Keys.NumPad9)
    //{
    if (e.KeyValue < 58 && e.KeyValue > 47 || e.KeyValue < 106 && e.KeyValue > 95)
    {
        int index1 = maskedTextBox1.SelectionStart; // cursor position
        if (index1 < maskedTextBox1.Text.Length)
        {
            string modified = maskedTextBox1.Text.Remove(index1, 1);
            maskedTextBox1.Text = modified.Insert(index1, character);
            if (index1 < maskedTextBox1.Text.Length - 1 && maskedTextBox1.Text[index1 + 1] == '/')
            {
                maskedTextBox1.SelectionStart = index1 + 2;
            }
            else
            {
                maskedTextBox1.SelectionStart = index1 + 1;
            }
        }
    }
    //}
}

When using the Chinese input method, there will be a case where KeyData is always "ProcessKey" and KeyValue is always 229.

In order to solve it, we can disable Chinese input by disabling IME.

maskedTextBox1.ImeMode = ImeMode.Disable;