C#

//#!csc.exe /t:winexe Test.cs
//
 
using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Windows.Forms;
 
class Test : Form
{
  static void Main()
  {
    Application.Run(new Test());
  }
 
  StringFormat format;
  Font watermarkFont;
 
  Test()
  {
    format = StringFormat.GenericDefault;
    format.Alignment = StringAlignment.Center;
    format.LineAlignment = StringAlignment.Center;
 
    watermarkFont = new Font(Font.FontFamily, 30f, FontStyle.Bold);
 
    SetStyle(ControlStyles.AllPaintingInWmPaint | ControlStyles.DoubleBuffer|
        ControlStyles.ResizeRedraw | ControlStyles.UserPaint, true);
 
    RichTextBox rtb = new RichTextBox();
    Controls.Add(rtb);
    rtb.Location = new Point(8, 8);
    rtb.Size = new Size(100, 60);
 
    Text = "Watermark Example";
  }
 
  protected override void OnPaint(PaintEventArgs e)
  {
    base.OnPaint(e);
 
    Graphics g = e.Graphics;
    g.DrawString("Watermark", watermarkFont, SystemBrushes.ControlDark,
      new PointF(Width / 2f, Height / 2f), format);
  }
}

//#!csc.exe /t:winexe /unsafe Test.cs
 
using System;
using System.ComponentModel;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Windows.Forms;
 
class Test : Form
{
  static void Main()
  {
    Application.Run(new Test());
  }
 
  Test()
  {
    Watermark w = new Watermark();
    Controls.Add(w);
    w.Dock = DockStyle.Fill;
    w.Font = new Font(Font.FontFamily, 48f, FontStyle.Bold);
    w.ForeColor = SystemColors.ControlDark;
    w.Text = "Example";
 
    TextBox tb = new TextBox();
    Controls.Add(tb);
    tb.Location = new Point(8, 8);
 
    Text = "Watermark Example";
  }
}
 
public class Watermark : Control
{
  StringFormat format;
  GraphicsPath path;
  Brush brush;
 
  public Watermark()
  {
    SetStyle(ControlStyles.AllPaintingInWmPaint |
        ControlStyles.DoubleBuffer | ControlStyles.ResizeRedraw |
        ControlStyles.UserPaint, true);
 
    format = StringFormat.GenericDefault;
    format.Alignment = StringAlignment.Center;
    format.LineAlignment = StringAlignment.Center;
 
    brush = new SolidBrush(ForeColor);
 
    OnResize(EventArgs.Empty);
  }
 
  public override Color ForeColor
  {
    get { return base.ForeColor; }
    set
    {
      brush = new SolidBrush(value);
      base.ForeColor = value;
    }
  }
 
  [DefaultValue(StringAlignment.Center)]
  public StringAlignment HorizontalAlignment
  {
    get { return format.Alignment; }
    set { format.Alignment = value; }
  }
 
  [DefaultValue(StringAlignment.Center)]
  public StringAlignment VerticalAlignment
  {
    get { return format.LineAlignment; }
    set { format.LineAlignment = value; }
  }
 
  protected override void OnHandleCreated(EventArgs e)
  {
    base.OnHandleCreated(e);
    Refresh();
  }
 
  protected override void OnResize(EventArgs e)
  {
    base.OnResize(e);
 
    path = new GraphicsPath();
    path.AddString(Text, Font.FontFamily, (int)Font.Style,
      Font.Size, new PointF(Width / 2f, Height / 2f), format);
 
    Region = new Region(path);
  }
 
  protected override void OnPaint(PaintEventArgs e)
  {
    base.OnPaint(e);
 
    e.Graphics.FillPath(brush, path);
  }
}

private const Int32 WM_CLOSE = 0x0010;
[DllImport("user32.dll")]
static extern IntPtr SendMessage(IntPtr hWnd, uint Msg, IntPtr wParam, IntPtr lParam);