最近公司有个需求是，拖动文件到桌面图标上，自动打开文件。那么只需在OnStartup事件中通过StartupEventArgs获取文件名然后进行操作即可。操作之后发现当软件已经启动了（单例运行），那么将无法将参数传给业务层。原因是因为跨进程了，那么我们可以通过窗口句柄的方式来进行通讯。
1 public partial class App : Application
2 {
3 private static Mutex AppMutex;
4 public App()
5 {
6
7 }
8
9 protected override void OnStartup(StartupEventArgs e)
10 {
11 //获取启动参数
12 var param = string.Empty;
13 if (e.Args.Length > 0)
14 {
15 param = e.Args[0].ToString();
16 }
17
18 //WpfApp8 = 你的项目名称
19 AppMutex = new Mutex(true, "WpfApp8", out var createdNew);
20
21 if (!createdNew)
22 {
23 var current = Process.GetCurrentProcess();
24
25 foreach (var process in Process.GetProcessesByName(current.ProcessName))
26 {
27 if (process.Id != current.Id)
28 {
29 Win32Helper.SetForegroundWindow(process.MainWindowHandle);
30 Win32Helper.SendMessageString(process.MainWindowHandle, param);
31 break;
32 }
33 }
34 Environment.Exit(0);
35 }
36 else
37 {
38 base.OnStartup(e);
39 }
40 }
41 } 1 public class Win32Helper
2 {
3 [DllImport("user32.dll", ExactSpelling = true, CharSet = CharSet.Auto)]
4 public static extern bool SetForegroundWindow(IntPtr hWnd);
5
6 /// <summary>
7 /// 发送消息
8 /// </summary>
9 /// <param name="hWnd"></param>
10 /// <param name="Msg"></param>
11 /// <param name="wParam"></param>
12 /// <param name="lParam"></param>
13 /// <returns></returns>
14 [DllImport("user32.dll")]
15 public static extern IntPtr SendMessage(IntPtr hWnd, int Msg, IntPtr wParam, ref COPYDATASTRUCT lParam);
16
17 // 声明常量
18 public const int WM_COPYDATA = 0x004A;
19
20 // 定义 COPYDATASTRUCT 结构
21 [StructLayout(LayoutKind.Sequential)]
22 public struct COPYDATASTRUCT
23 {
24 public IntPtr dwData;
25 public int cbData;
26 public IntPtr lpData;
27 }
28
29 /// <summary>
30 /// 发送字符串消息
31 /// </summary>
32 /// <param name="hWnd"></param>
33 /// <param name="message"></param>
34 public static void SendMessageString(IntPtr hWnd, string message)
35 {
36 if (string.IsNullOrEmpty(message)) return;
37
38 byte[] messageBytes = Encoding.Unicode.GetBytes(message + '\0'); // 添加终止符
39
40 COPYDATASTRUCT cds = new COPYDATASTRUCT();
41 cds.dwData = IntPtr.Zero;
42 cds.cbData = messageBytes.Length;
43 cds.lpData = Marshal.AllocHGlobal(cds.cbData);
44 Marshal.Copy(messageBytes, 0, cds.lpData, cds.cbData);
45 try
46 {
47 SendMessage(hWnd, WM_COPYDATA, IntPtr.Zero, ref cds);
48 }
49 finally
50 {
51 //释放分配的内存，即使发生异常也不会泄漏资源
52 Marshal.FreeHGlobal(cds.lpData);
53 }
54 }
55 } 1 public partial class MainWindow : Window
2 {
3 public MainWindow()
4 {
5 InitializeComponent();
6 }
7
8 protected override void OnSourceInitialized(EventArgs e)
9 {
10 base.OnSourceInitialized(e);
11
12 HwndSource hwndSource = PresentationSource.FromVisual(this) as HwndSource;
13 hwndSource.AddHook(WndProc);
14 }
15
16 private IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
17 {
18 if (msg == WM_COPYDATA)
19 {
20 COPYDATASTRUCT cds = (COPYDATASTRUCT)Marshal.PtrToStructure(lParam, typeof(COPYDATASTRUCT));
21 string receivedMessage = Marshal.PtrToStringUni(cds.lpData);
22
23 Console.WriteLine("收到消息：" + receivedMessage);
24
25 //TODO:业务处理
26 MessageBox.Show(receivedMessage);
27
28 handled = true;
29 }
30
31 return IntPtr.Zero;
32 }
33 }