Watermark Text Box

What it is for

Use it in place of a TextBox wherever a label beside the box would take room the form does not have, or where a hint of the expected input helps more than a caption. The prompt – the watermark – disappears as soon as the user clicks into the box or the box holds text, and comes back when the box is left empty.

How it works

• The control hosts an ordinary multi-line text box and, laid over it, a WatermarkProvider that draws the prompt. A click anywhere on the prompt hides it and puts the caret in the text box.
• Text is the text the user typed; it follows the inner text box as the user types, and Control.TextChanged is raised for each change.
• The prompt is shown when IsWatermarkEnabled is true, Text is empty and the control does not have the focus.

Appearance

WatermarkText, WatermarkTextFont, WatermarkTextForeColor and WatermarkBackColor style the prompt; WatermarkImage with ShouldRenderWatermarkImage adds a picture to the left of it. The control draws a one-pixel border in BorderColor round the box.

using System;
using System.Drawing;
using System.Windows.Forms;
using Binarymission.WinForms.Controls.InputControls;

public class CourierNotesForm : Form
{
    private readonly WatermarkTextBox notesBox;
    private readonly Label characterCount;

    public CourierNotesForm()
    {
        Text = "Delivery instructions";
        ClientSize = new Size(420, 180);

        notesBox = new WatermarkTextBox
        {
            Location = new Point(12, 12),
            Size = new Size(396, 120),
            WatermarkText = "Notes for the courier - gate codes, safe places, opening hours",
            WatermarkTextForeColor = SystemColors.GrayText,
            WatermarkTextFont = new Font("Segoe UI", 9f, FontStyle.Italic),
            BorderColor = SystemColors.ControlDark,
            TextScrollBars = ScrollBars.Vertical
        };
        notesBox.TextChanged += (sender, e) =>
            characterCount.Text = notesBox.Text.Length + " / 500 characters";

        characterCount = new Label { Location = new Point(12, 142), AutoSize = true };

        Controls.Add(notesBox);
        Controls.Add(characterCount);
    }
}