Watermark TextBox in WinForms

Question

Can anyone point me to a good implementation of a basic Windows Forms TextBox that will initially show watermark text that disappears when the cursor enters it? I think I ca

Answer 1

using System;
using System.ComponentModel;
using System.Drawing;
using System.Windows.Forms;

namespace PlaceHolderTextBoxCSharp
{
    public class CTextBox : TextBox
    {
        private Panel contenedor;
        protected string texto = "PlaceHolderText";
        protected Color colorTextoDefault = Color.Gray;
        public Color colorTexto = Color.Gray;
        protected Color colorTextoObligatorio = Color.Red;
        private Font fuente;
        private SolidBrush establecerColorTexto;
        private bool obligatoriedad = false;
        private bool colorConFoco = false;
        private int vuelta = 0;

        public CTextBox()
        {
            Inicializar();
        }

        private void Inicializar()
        {
            fuente = Font;
            CharacterCasing = CharacterCasing.Upper;
            contenedor = null;

            MuestraPlaceHolder();

            Leave += new EventHandler(PierdeFoco);
            TextChanged += new EventHandler(CambiaTexto);
        }

        private void EliminaPlaceHolder()
        {
            if (contenedor != null)
            {
                Controls.Remove(contenedor);
                contenedor = null;
            }
        }

        private void MuestraPlaceHolder()
        {
            if (contenedor == null && TextLength <= 0)
            {
                contenedor = new Panel();
                contenedor.Paint += new PaintEventHandler(contenedorPaint);
                contenedor.Invalidate();
                contenedor.Click += new EventHandler(contenedorClick);
                Controls.Add(contenedor);
            }
        }

        private void contenedorClick(object sender, EventArgs e)
        {
            Focus();
        }

        private void contenedorPaint(object sender, PaintEventArgs e)
        {
            contenedor.Location = new Point(2, 0);
            contenedor.Height = Height;
            contenedor.Width = Width;
            contenedor.Anchor = AnchorStyles.Left | AnchorStyles.Right;
            establecerColorTexto = new SolidBrush(colorTexto);
            Graphics g = e.Graphics;
            g.DrawString(texto, fuente, establecerColorTexto, new PointF(-1f, 1f));
        }

        private void PierdeFoco(object sender, EventArgs e)
        {
            if (TextLength > 0)
            {
                EliminaPlaceHolder();
            }
            else
            {
                if (obligatoriedad == true)
                {
                    colorTexto = colorTextoObligatorio;
                }
                else
                {
                    colorTexto = colorTextoDefault;
                }

                Invalidate();
            }
        }

        private void CambiaTexto(object sender, EventArgs e)
        {
            if (TextLength > 0)
            {
                EliminaPlaceHolder();
            }
            else
            {
                MuestraPlaceHolder();

                vuelta += 1;

                if (vuelta >= 1 && obligatoriedad == true)
                {
                    colorTexto = colorTextoObligatorio;
                }
            }
        }

        protected override void OnPaint(PaintEventArgs e)
        {
            base.OnPaint(e);
            MuestraPlaceHolder();
        }

        protected override void OnInvalidated(InvalidateEventArgs e)
        {
            base.OnInvalidated(e);

            if (contenedor != null)
            {
                contenedor.Invalidate();
            }
        }

        [Category("Atributos PlaceHolder")]
        [Description("Establece el texto a mostrar.")]

        public string PlaceHolderText
        {
            get
            {
                return texto;
            }
            set
            {
                texto = value;
                Invalidate();
            }
        }

        [Category("Atributos PlaceHolder")]
        [Description("Establece el estilo de fuente del PlaceHolder.")]

        public Font PlaceHolderFont
        {
            get
            {
                return fuente;
            }
            set
            {
                fuente = value;
                Invalidate();
            }
        }

        [Category("Atributos PlaceHolder")]
        [Description("Indica si el campo es obligatorio.")]

        public bool PlaceHolderFieldRequired
        {
            get
            {
                return obligatoriedad;
            }
            set
            {
                obligatoriedad = value;
                Invalidate();
            }
        }
    }
}