Principal.cs

using System;
using System.Windows.Forms;

namespace R708RestringirEntradaCampoTexto
{
    public partial class Principal : Form
    {
        public Principal()
        {
            InitializeComponent();
        }

        private void btnHora_Click(object sender, EventArgs e)
        {
            mskEntrada.UseSystemPasswordChar = false;
            mskEntrada.Mask = "00:00";
            lblTipoRestriccion.Text = mskEntrada.Mask;
            mskEntrada.Focus();
        }

        private void btnCodigoPostalEstadosUnidos_Click(object sender, EventArgs e)
        {
            mskEntrada.UseSystemPasswordChar = false;
            mskEntrada.Mask = "00000-9999";
            lblTipoRestriccion.Text = mskEntrada.Mask;
            mskEntrada.Focus();
        }

        private void btnCodigoPostalReinoUnido_Click(object sender, EventArgs e)
        {
            mskEntrada.UseSystemPasswordChar = false;
            mskEntrada.Mask = ">LCCC 9LL";
            lblTipoRestriccion.Text = mskEntrada.Mask;
            mskEntrada.Focus();
        }

        private void btnMoneda_Click(object sender, EventArgs e)
        {
            mskEntrada.UseSystemPasswordChar = false;
            mskEntrada.Mask = "$999,999.00";
            lblTipoRestriccion.Text = mskEntrada.Mask;
            mskEntrada.Focus();
        }

        private void btnFecha_Click(object sender, EventArgs e)
        {
            mskEntrada.UseSystemPasswordChar = false;
            mskEntrada.Mask = "00/00/0000";
            lblTipoRestriccion.Text = mskEntrada.Mask;
            mskEntrada.Focus();
        }

        private void btnClave_Click(object sender, EventArgs e)
        {
            mskEntrada.UseSystemPasswordChar = true;
            mskEntrada.Mask = "0000";
            lblTipoRestriccion.Text = mskEntrada.Mask;
            mskEntrada.Focus();
        }

        private void Principal_Load(object sender, EventArgs e)
        {

        }
    }
}