[VS.NET2005][C#]TextBoxを継承したコントロールで･･･

public class MyTextBox : System.Windows.Forms.TextBox
{
    public MyTextBox() : base()
    {
    }

    private Color _disableBackColor = System.Drawing.SystemColors.Window;
    [Category("表示"), Description("コンポーネントの使用不可時の背景色です。")]
    public Color DisableBackColor
    {
        get { return _disableBackColor; }
        set { _disableBackColor = value; }
    }

    private Color _disableForeColor = System.Drawing.SystemColors.WindowText;
    [Category("表示"), Description("テキストを表示するのに使用される、このコンポーネントの使用不可時の前景色です。")]
    public Color DisableForeColor
    {
        get { return _disableForeColor; }
        set { _disableForeColor = value; }
    }

    protected override void OnEnabledChanged(EventArgs e)
    {
        base.SetStyle(ControlStyles.UserPaint, !this.Enabled);
        base.OnEnabledChanged(e);
    }

    protected override void OnPaintBackground(PaintEventArgs pevent)
    {
        base.OnPaintBackground(pevent);
        pevent.Graphics.FillRectangle(new SolidBrush(this.DisableBackColor), 0, 0, this.Width - 1, this.Height - 1);
    }

    protected override void OnPaint(PaintEventArgs e)
    {
        int w = base.Width;
        int h = base.Height;

        base.OnPaint(e);

        TextFormatFlags tff = TextFormatFlags.Default;
        switch (base.TextAlign)
        {
            case HorizontalAlignment.Center:
                tff |= TextFormatFlags.HorizontalCenter;
                break;
            case HorizontalAlignment.Left:
                tff |= TextFormatFlags.Left;
                break;
            case HorizontalAlignment.Right:
                tff |= TextFormatFlags.Right;
                break;
        }
        TextRenderer.DrawText(e.Graphics, base.Text, base.Font, new Rectangle(-1, 1, w -1, h), this.DisableForeColor, tff);
    }
}

base.SetStyle(ControlStyles.UserPaint, !this.Enabled);
base.OnEnabledChanged(e);

base.SetStyle(ControlStyles.UserPaint, !this.Enabled);
base.RecreateHandle();
base.OnEnabledChanged(e);