托盘显示许多软件都有这个功能，在C#中如何实现呢，下面的方法可以实现托盘显示，不过可能有些复杂。
首先，需要在工具栏拖入NotifyIcon，如图1的那个控件。

图一：

然后，设置NotifyIcon的属性，加图标什么的。
最后，最主要的，就是NotifyIcon点击事件，要实现点击托盘图标隐藏窗口，再点击显示窗口，还有右键托盘能显示菜单等。
下面着重介绍一下这一部分的实现。
一、点击托盘右键菜单
这个NotifyIcon本身就有这个属性，即NotifyIcon.ContextMenu，添加相应菜单即可。
详见托盘显示演示的 AddTrayMenuItem()方法。
二、隐藏至托盘和显示
该部分使用user32.dll中的函数，如下：
1、bool SetWindowPos( IntPtr hWnd, IntPtr hWndAfter, int x, int y, int cx, int cy, uint flags)
函数功能:
该函数改变一个子窗口，弹出式窗口式顶层窗口的尺寸，位置和Z序。 　　子窗口，弹出式窗口，及顶层窗口根据它们在屏幕上出现的顺序排序、顶层窗口设置的级别最高，并且被设置为Z序的第一个窗口。
2、IntPtr FindWindowEx(IntPtr hwndParent,IntPtr hwndChildAfter,string lpszClass,string lpszWindow)
函数功能:
该函数获得一个窗口的句柄，该窗口的类名和窗口名与给定的字符串相匹配。这个函数查找子窗口，从排在给定的子窗口后面的下一个子窗口开始。在查找时不区分大小写。
3、int GetWindowRect(IntPtr hwnd, ref RECT lpRect)
函数功能：
该函数返回指定窗口的边框矩形的尺寸。该尺寸以相对于屏幕坐标左上角的屏幕坐标给出。
4、DrawAnimatedRects( IntPtr hwnd, int ani, ref RECT from,ref RECT to)
函数功能：
在窗口缩放时产生动画效果

部分代码如下：

ChangeTrayStateManager类：

public class ChangeTrayStateManager{public static void Animate( IntPtr handle, Rectangle fromRect, Rectangle toRect){try{TrayStateMethods.RECT from = TrayStateMethods.RECT.FromRectangle(fromRect);TrayStateMethods.RECT to = TrayStateMethods.RECT.FromRectangle(toRect);TrayStateMethods.DrawAnimatedRects(handle,TrayStateMethods.IDANI_CAPTION,ref from,ref to);}catch{ }}public static void Animate( Form animateForm, Control owner){Animate(animateForm.Handle, animateForm.Bounds, owner.RectangleToScreen(owner.ClientRectangle));}public static void Animate(  Form animateForm,Rectangle bounds,bool minimized){try{if (minimized){Animate( animateForm.Handle, GetNotificationRect(), animateForm.Bounds);}else{Animate(animateForm.Handle, animateForm.Bounds, GetNotificationRect());}}catch{ }}private static Rectangle GetNotificationRect(){TrayStateMethods.RECT rect = new TrayStateMethods.RECT();IntPtr hwnd = TrayStateMethods.FindWindowEx( IntPtr.Zero, IntPtr.Zero,"Shell_TrayWnd", null);if (hwnd == IntPtr.Zero){throw new Win32Exception();}hwnd = TrayStateMethods.FindWindowEx(hwnd, IntPtr.Zero,"TrayNotifyWnd", null);if (hwnd == IntPtr.Zero){throw new Win32Exception();}hwnd = TrayStateMethods.FindWindowEx( hwnd, IntPtr.Zero, "SysPager",  null);if (hwnd == IntPtr.Zero){throw new Win32Exception();}hwnd = TrayStateMethods.FindWindowEx( hwnd,IntPtr.Zero,"ToolbarWindow32", null);if (hwnd == IntPtr.Zero){throw new Win32Exception();}TrayStateMethods.GetWindowRect(hwnd, ref rect);return rect.Rect;}}

TrayStateMethods类，引用user32.dll方法。

  public class TrayStateMethods{public const int IDANI_CAPTION = 0x3;public const int WM_SYSCOMMAND = 0x0112;public const uint SWP_NOZORDER = 0x0004;public const uint SWP_NOREDRAW = 0x0008;public const int HWND_TOPMOST = -1;public const int SW_HIDE = 0x0;public const int SW_NORMAL = 0x1;public const int SW_RESTORE = 9;public const int SW_MAXIMIZE = 3;public enum SystemCommands{SC_SIZE = 0xF000,SC_MOVE = 0xF010,SC_MINIMIZE = 0xF020,SC_MAXIMIZE = 0xF030,SC_MAXIMIZE2 = 0xF032,	SC_NEXTWINDOW = 0xF040,SC_PREVWINDOW = 0xF050,SC_CLOSE = 0xF060,SC_VSCROLL = 0xF070,SC_HSCROLL = 0xF080,SC_MOUSEMENU = 0xF090,SC_KEYMENU = 0xF100,SC_ARRANGE = 0xF110,SC_RESTORE = 0xF120,SC_RESTORE2 = 0xF122,	SC_TASKLIST = 0xF130,SC_SCREENSAVE = 0xF140,SC_HOTKEY = 0xF150,SC_DEFAULT = 0xF160,SC_MONITORPOWER = 0xF170,SC_CONTEXTHELP = 0xF180,SC_SEPARATOR = 0xF00F}[StructLayout(LayoutKind.Sequential)]public struct RECT{public int Left;public int Top;public int Right;public int Bottom;public RECT(int left, int top, int right, int bottom){this.Left = left;this.Top = top;this.Right = right;this.Bottom = bottom;}public Rectangle Rect{get{return new Rectangle(this.Left, this.Top, this.Right - this.Left, this.Bottom - this.Top);}}public static RECT FromXYWH(int x, int y, int width, int height){return new RECT(x,y,x + width,y + height);}public static RECT FromRectangle(Rectangle rect){return new RECT(rect.Left,rect.Top,rect.Right,rect.Bottom);}}[DllImport("user32.dll")]public static extern IntPtr FindWindowEx(IntPtr hwndParent,IntPtr hwndChildAfter,string lpszClass,string lpszWindow);[DllImport("user32.dll")]public static extern int GetWindowRect(IntPtr hwnd, ref RECT lpRect);[DllImport("user32.dll")]public static extern bool DrawAnimatedRects(IntPtr hwnd,int ani,ref RECT from,ref RECT to);[DllImport("user32.dll")][return: MarshalAs(UnmanagedType.Bool)]public static extern bool SetWindowPos(IntPtr hWnd,IntPtr hWndAfter,int x,int y,int cx,int cy,uint flags);}

主界面调用：

   public partial class Form1 : Form{private bool isInTray = false;private Rectangle rectBounds;public Form1(){InitializeComponent();new Thread(new ThreadStart(AddTrayMenuItem)).Start();}#region Eventprivate void notifyIcon1_MouseClick(object sender, MouseEventArgs e){if (e.Button == MouseButtons.Left){if (isInTray){ShowForm();}else{MiniToTray();}}}private void Form1_Load(object sender, EventArgs e){this.WindowState = FormWindowState.Normal;}void hideItem_Click(object sender, EventArgs e){MiniToTray();}void showItem_Click(object sender, EventArgs e){ShowForm();}void exitItem_Click(object sender, EventArgs e){this.Close();} #endregion#region Methodprivate void AddTrayMenuItem(){ContextMenu cm = new ContextMenu();MenuItem showItem = new MenuItem("显示主界面");showItem.Click += new EventHandler(showItem_Click);MenuItem miSeparator0 = new MenuItem("-");miSeparator0.Enabled = false;MenuItem hideItem = new MenuItem("最小化到托盘");hideItem.Click += new EventHandler(hideItem_Click);MenuItem miSeparator1 = new MenuItem("-");miSeparator1.Enabled = false;MenuItem exitItem = new MenuItem("退出");exitItem.Click += new EventHandler(exitItem_Click);cm.MenuItems.AddRange(new MenuItem[] { showItem, miSeparator0, hideItem, miSeparator1, exitItem });this.notifyIcon1.ContextMenu = cm;this.notifyIcon1.ContextMenu.MenuItems[0].Visible = false;this.notifyIcon1.ContextMenu.MenuItems[1].Visible = false;}private void MiniToTray(){ChangeTrayStateManager.Animate(this, Bounds, false);rectBounds = Bounds;Hide();isInTray = true;this.notifyIcon1.ContextMenu.MenuItems[0].Visible = true;this.notifyIcon1.ContextMenu.MenuItems[1].Visible = true;this.notifyIcon1.ContextMenu.MenuItems[2].Visible = false;this.notifyIcon1.ContextMenu.MenuItems[3].Visible = false;}private void ShowForm(){if (isInTray){TrayStateMethods.SetWindowPos(Handle,new IntPtr(-1),rectBounds.X,rectBounds.Y,rectBounds.Width,rectBounds.Height,TrayStateMethods.SWP_NOREDRAW | TrayStateMethods.SWP_NOZORDER);ChangeTrayStateManager.Animate(this, rectBounds, true);this.Show();this.Activate();isInTray = false;this.notifyIcon1.ContextMenu.MenuItems[0].Visible = false;this.notifyIcon1.ContextMenu.MenuItems[1].Visible = false;this.notifyIcon1.ContextMenu.MenuItems[2].Visible = true;this.notifyIcon1.ContextMenu.MenuItems[3].Visible = true;if (this.WindowState == FormWindowState.Minimized){this.WindowState = FormWindowState.Normal;}}}#endregion}

详见工程  托盘显示演示