最近看到有人问如何做一个“桌面天气秀”类似的软件，开始我以为做这个东西很复杂，因为觉得至少要传递Message给Desktop。但事实上，一试之后发现做这个程序竟然很简单。

以下就把做的步骤列出来，供大家参考。

首先，需要设置窗体样式，这里面要设置的有：

l         设置FormBorderStyle为None；

l         设置TopMost为false；

l         设置ShowInTaskbar为false；

l         为了能穿透桌面，要把BackColor设为White，在把TransparentKey设为White；

这样，窗体的基本设置就完成了，为了显示要画的内容，则需要在窗体的Paint事件中去做，我这里所画的内容是显示当前月的所有天，相当于一个小日历。

private void Draw( Graphics g )

{

    const float REG_HEIGHT = 30f;

    const float START_POS_X = 0f;

    const float START_POS_Y = 0f;

    const int BLANK_SPACE_NUM = 5;

    // Draw day of week signal

    RectangleF recRegion = new RectangleF( START_POS_X, START_POS_Y,

        (float)(this.Width), REG_HEIGHT );

    const string FORMAT_STRING = "{0}{1}{2}{3}{4}{5}{6}";

    string strDraw = string.Format( FORMAT_STRING,

        "SUN".PadLeft( BLANK_SPACE_NUM, ' ' ),

        "MON".PadLeft( BLANK_SPACE_NUM, ' ' ),

        "TUE".PadLeft( BLANK_SPACE_NUM, ' ' ),

        "WED".PadLeft( BLANK_SPACE_NUM, ' ' ),

        "THU".PadLeft( BLANK_SPACE_NUM, ' ' ),

        "FRI".PadLeft( BLANK_SPACE_NUM, ' ' ),

        "SAT".PadLeft( BLANK_SPACE_NUM, ' ' ) );

    Font myFont = new Font( "宋体", 11, FontStyle.Bold );

    StringFormat sfDraw = new StringFormat();

    sfDraw.Alignment = StringAlignment.Near;

    sfDraw.LineAlignment = StringAlignment.Far;

    Brush brDraw = new SolidBrush( Color.Wheat );

    g.DrawString( strDraw, myFont, brDraw, recRegion, sfDraw );

    DateTime dtFirstDate = DateTime.Now.AddDays( 1 - DateTime.Now.Day );

    int nStartIndex = (int)(dtFirstDate.DayOfWeek);

    nStartIndex++;

    TimeSpan tsDays = dtFirstDate.AddMonths( 1 ) - dtFirstDate;

    // Draw every day in this month

    strDraw = "";

    int i = 0;

    for( ; i < tsDays.Days; i++ )

    {

        switch( dtFirstDate.AddDays( i ).DayOfWeek )

        {

            case DayOfWeek.Sunday:

            case DayOfWeek.Monday:

            case DayOfWeek.Tuesday:

            case DayOfWeek.Wednesday:

            case DayOfWeek.Thursday:

            case DayOfWeek.Friday:

                strDraw += (i+1).ToString().PadLeft( BLANK_SPACE_NUM, ' ');

                break;

            case DayOfWeek.Saturday:

                strDraw += (i+1).ToString().PadLeft( BLANK_SPACE_NUM, ' ');

                strDraw = strDraw.PadLeft( BLANK_SPACE_NUM * 7, ' ' );

                recRegion = new RectangleF( START_POS_X,

                    START_POS_Y + REG_HEIGHT * ( 1 + ( (i+1) + nStartIndex - 7 ) / 7 ),

                    (float)(this.Width), REG_HEIGHT );

                g.DrawString( strDraw, myFont, brDraw, recRegion, sfDraw );

                strDraw = "";

                break;

        }

    }

    if( strDraw != "" )

    {

        strDraw = strDraw.PadRight( BLANK_SPACE_NUM * 7, ' ' );

        recRegion = new RectangleF( START_POS_X,

            START_POS_Y + REG_HEIGHT * ( 1 + ( i + nStartIndex - 7 ) / 7 + 1 ),

            (float)(this.Width), REG_HEIGHT );

        g.DrawString( strDraw, myFont, brDraw, recRegion, sfDraw );

    }

}

private void frmSprite_Paint(object sender, System.Windows.Forms.PaintEventArgs e)

{

    Graphics g = e.Graphics;

    Draw( g );

}

为了窗体能方便的退出，我加了一个NotifyIcon和ContextMenu来处理，具体如下。

private System.Windows.Forms.NotifyIcon ntfSprite;

private System.Windows.Forms.ContextMenu mnuContext;

private System.Windows.Forms.MenuItem mnuExit;

private void mnuExit_Click(object sender, System.EventArgs e)

{

    this.Close();

}

       本来以为自己的窗体放在Desktop之前，会影响窗体下Desktop的某些操作，但事实，这一点根本不用担心，因为.Net框架已经替你做了，因此你不用再调用API来传递消息。

如果想要所显示的窗体能够随意拖动，这可以参看我另外一篇文章：

http://blog.csdn.net/knight94/archive/2006/04/14/663089.aspx

以上的代码只是做了简单的测试，大家可以在我的基础上做扩展，例如调用Api来对当前进程作一些隐藏，设置窗体的起始位置，以及一些界面操作之类，放到启动菜单，这些都是可以完成的，我这里就不罗嗦了