一、自定义窗体，一般为规则的图形，如圆、椭圆等。
做法：重写Form1_Paint事件（Form1是窗体的名字），最简单的一种情况如下：System.Drawing.Drawing2D.GraphicsPath shape = new System.Drawing.Drawing2D.GraphicsPath();shape.AddEllipse(0,0,this.Height, this.Width);this.Region = new Region(shape);即重绘窗体的规则。
二、利用背景图片实现1.设置窗体的背景图片，其中背景图片是24位（不包括24）以下的位图（BMP图片），并且要设置TansparencyKey的值，一般为你背景图片的背景色，即创建不规则图片时的底色，一般设为你图片中没有的颜色。
这种做法的不好的地方就是背景图片一定要16位或者更低的，而且还要确保客户端的显示。
如果监视器的颜色深度设置大于24 位，则不管TransparencyKey 属性是如何设置的，窗体的非透明部分都会产生显示问题。
若要避免出现这种问题，请确保“显示”控制面板中的监视器颜色深度的设置小于24 位。
当开发具有这种透明功能的应用程序时，请牢记应使您的用户意识到此问题。
实现步骤如下：1．新建windows application2．选择窗体，找到BackgroundImage属性，点击打开新的窗口，选择下面的导入资源文件，选择你的不规则的BMP图片3．找到窗体的TansparencyKey，将它设置为你背景图片的背景色（如黄色）4．找到窗体的FormBorderStyle，将其设置为none，即不显示标题栏5．运行<!--[endif]-->2.跟背景图片一样的图形，不过是动态加载，遍历位图以实现不规则窗体。
它的原理是这样的，在Form的load事件中写方法使得窗体的描绘区域发生改变。
实现步骤如下：1．建立winform应用程序2．找到窗体的Load事件，双击进行编辑3．编写方法，主要的代码如下：代码class BitmapRegion{public BitmapRegion(){ }///<summary>/// Create and apply the region on the supplied control///创建支持位图区域的控件（目前有button和form）///</summary>///<param name="control">The Control object to apply the reg ion to控件</param>///<param name="bitmap">The Bitmap object to create the regi on from位图</param>public static void CreateControlRegion(Control control, Bitma p bitmap){// Return if control and bitmap are null//判断是否存在控件和位图if (control == null || bitmap == null)return;// Set our control''s size to be the same as the bitmap //设置控件大小为位图大小control.Width = bitmap.Width;control.Height = bitmap.Height;// Check if we are dealing with Form here//当控件是form时if (control is System.Windows.Forms.Form){// Cast to a Form object//强制转换为FORMForm form = (Form)control;// Set our form''s size to be a little larger that th e bitmap just// in case the form''s border style is not set to non e in the first place//当FORM的边界FormBorderStyle不为NONE时，应将FORM的大小设置成比位图大小稍大一点form.Width = control.Width;form.Height = control.Height;// No border//没有边界form.FormBorderStyle = FormBorderStyle.None;// Set bitmap as the background image//将位图设置成窗体背景图片form.BackgroundImage = bitmap;// Calculate the graphics path based on the bitmap su pplied//计算位图中不透明部分的边界GraphicsPath graphicsPath = CalculateControlGraphicsP ath(bitmap);// Apply new region//应用新的区域form.Region = new Region(graphicsPath);}// Check if we are dealing with Button here//当控件是button时else if (control is System.Windows.Forms.Button){// Cast to a button object//强制转换为 buttonButton button = (Button)control;// Do not show button text//不显示button textbutton.Text = "";// Change cursor to hand when over button//改变 cursor的stylebutton.Cursor = Cursors.Hand;// Set background image of button//设置button的背景图片button.BackgroundImage = bitmap;// Calculate the graphics path based on the bitmap su pplied//计算位图中不透明部分的边界GraphicsPath graphicsPath = CalculateControlGraphicsP ath(bitmap);// Apply new region//应用新的区域button.Region = new Region(graphicsPath);}}///<summary>/// Calculate the graphics path that representing the figure in the bitmap/// excluding the transparent color which is the top left pix el./// //计算位图中不透明部分的边界///</summary>///<param name="bitmap">The Bitmap object to calculate our g raphics path from</param>///<returns>Calculated graphics path</returns>private static GraphicsPath CalculateControlGraphicsPath(Bitm ap bitmap){// Create GraphicsPath for our bitmap calculation//创建 GraphicsPathGraphicsPath graphicsPath = new GraphicsPath();// Use the top left pixel as our transparent color//使用左上角的一点的颜色作为我们透明色Color colorTransparent = bitmap.GetPixel(0, 0);// This is to store the column value where an opaque pixe l is first found.// This value will determine where we start scanning for trailing opaque pixels.//第一个找到点的Xint colOpaquePixel = 0;// Go through all rows (Y axis)// 偏历所有行（Y方向）for (int row = 0; row < bitmap.Height; row++){// Reset value//重设colOpaquePixel = 0;// Go through all columns (X axis)//偏历所有列（X方向）for (int col = 0; col < bitmap.Width; col++){// If this is an opaque pixel, mark it and search for anymore trailing behind//如果是不需要透明处理的点则标记，然后继续偏历if (bitmap.GetPixel(col, row) != colorTransparent) {// Opaque pixel found, mark current position//记录当前colOpaquePixel = col;// Create another variable to set the current pixel position//建立新变量来记录当前点int colNext = col;// Starting from current found opaque pixel, search for anymore opaque pixels// trailing behind, until a transparent pixel is found or minimum width is reached///从找到的不透明点开始，继续寻找不透明点,一直到找到或则达到图片宽度for (colNext = colOpaquePixel; colNext < bitm ap.Width; colNext++)if (bitmap.GetPixel(colNext, row) == colo rTransparent)break;// Form a rectangle for line of opaque pixels found and add it to our graphics path//将不透明点加到graphics pathgraphicsPath.AddRectangle(new Rectangle(colOp aquePixel, row, colNext - colOpaquePixel, 1));// No need to scan the line of opaque pixels just foundcol = colNext;}}}// Return calculated graphics pathreturn graphicsPath;}}4．运行<!--[endif]-->三、调用类库实现主要就是根据一些坐标，然后根据这些坐标绘制窗体代码如下：代码public Form3(){InitializeComponent();//创建不规则窗体POINTAPI[] poin;poin = new POINTAPI[5];poin[0].x = 90;poin[0].y = 90;poin[1].x = this.Width;poin[1].y = 0;poin[2].x = Width;poin[2].y = this.Height / 2;poin[3].x = Width / 2;poin[3].y = Height / 2;poin[4].x = 0;poin[4].y = Width;Boolean flag = true;IntPtr hRgn = CreatePolygonRgn(ref poin[0], 8, 1); SetWindowRgn(this.Handle, hRgn, ref flag);this.BackColor = Color.BurlyWood;}[StructLayout(LayoutKind.Sequential)]private struct POINTAPI{internal int x;internal int y;}[DllImport("gdi32.dll")]private static extern IntPtr CreatePolygonRgn(ref POINTAPI lp Point,int nCount,int nPolyFillMode);[DllImport("user32.dll")]private static extern IntPtr SetWindowRgn(IntPtr hWnd,IntPtr hRgn, ref Boolean bRedraw);//设置窗体显示状态[DllImport("user32.dll")]private static extern int SetWindowPos(IntPtr hwnd,int hWndIn sertAfter,int x,int y,int cx,int cy,int wFlags);private void Start_Btn_Click(object sender, EventArgs e){//始终显示在前面SetWindowPos(this.Handle, -1, 0, 0, 0, 0, 1);}private void button1_Click(object sender, EventArgs e){//最小化始终显示在前面SetWindowPos(this.Handle, -1, 0, 0, 0, 0, 0);}当然，我们也可以自定义窗体的动作，如按着某个轨迹一定，下面的代码中的Backgroun dForm程序中就小试了一下，效果还不错，下面是这些程序的效果图（有点乱）和代码：代码是.Net 2.0的，也可以转换为其他版本的，只要运行主程序即可。
