محدود کردن Textbox در سی شارپ

private void textBox1_KeyPress (object sender, KeyPressEventArgs e)
{
    if (char.IsDigit(e.KeyChar) || e.KeyChar == (int) Keys.Back)
    {
        e.Handled = false;
    }
    else
    {
        e.Handled = true;
    }
}

private void textBox1_KeyPress (object sender, KeyPressEventArgs e)
{
    if (char.IsLower(e.KeyChar) || e.KeyChar == (int)Keys.Back)
    {
        e.Handled = false;
    }
    else
    {
        e.Handled = true;
    }
}

private void textBox1_KeyPress (object sender, KeyPressEventArgs e)
{
    if (char.IsUpper(e.KeyChar) || e.KeyChar == (int)Keys.Back)
    {
        e.Handled = false;
    }
    else
    {
        e.Handled = true;
    }
}

private void textBox1_KeyPress (object sender, KeyPressEventArgs e)
{
    if (char.IsLetter(e.KeyChar) || e.KeyChar == (int)Keys.Back)
    {
        e.Handled = false;
    }
    else
    {
        e.Handled = true;
    }
}