如何用C#做一个类似于桌面插件的程序？
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。
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