通过 C# 程序在资源管理器中显示多个选定文件的路径

当用户在 Explorer 中打开多个文件时，Explorer 大约会同时创建多个进程。但是，从进程开始到窗口准备好接收消息的那一刻要经过一段时间。因此需要稍微修改WM_COPYDATA 方法来处理这种情况：在主进程中添加等待窗口创建的等待，避免使用 MessageBox 因为它会阻塞执行等。

应用类：

using System;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Windows;
using System.Runtime.InteropServices;
using System.Diagnostics;

namespace WpfApp1
{

    public partial class App : Application
    {

        [DllImport("user32.dll")]
        public static extern IntPtr SendMessage(IntPtr hWnd, uint Msg, IntPtr wParam, ref COPYDATASTRUCT lParam);

        [StructLayout(LayoutKind.Sequential)]
        public struct COPYDATASTRUCT
        {
            public IntPtr dwData;
            public int cbData;
            public IntPtr lpData;
        }

        public const uint WM_COPYDATA = 0x004A;

        private void Application_Startup(object sender, StartupEventArgs e)
        {
            string command = "";
            string[] argv = Environment.GetCommandLineArgs();
            if (argv.Length > 1)
                command = argv[1];

            Process this_process = Process.GetCurrentProcess();
            Process main_process;

            //найти все процессы с таким же именем, запущенные ранее данного процесса
            Process[] other_processes =
                Process.GetProcessesByName(this_process.ProcessName)
                .Where(pr => { return pr.Id != this_process.Id && pr.StartTime <= this_process.StartTime;})
                .OrderBy((pr) => { return pr.StartTime; })
                .ToArray();

            //найти основной процесс
            if (other_processes.Length > 0) main_process = other_processes[0];
            else return;

            //ждем создания окна в основном процессе
            IntPtr hWnd;
            int c = 0;
            while (true)
            {
                hWnd = main_process.MainWindowHandle;
                if (hWnd != IntPtr.Zero) break;
                System.Threading.Thread.Sleep(100);
                c++;
                if (c > 10) { return; }
            }

            //отправляем команду
            var cds = new COPYDATASTRUCT();
            cds.dwData = (IntPtr)1;
            cds.cbData = (command.Length + 1) * 2;
            cds.lpData = Marshal.StringToHGlobalUni(command);
            SendMessage(hWnd, WM_COPYDATA, IntPtr.Zero, ref cds);
            Marshal.FreeHGlobal(cds.lpData);

            //завершаем работу
            Environment.Exit(0);    
        }        
    }
}

MainWindow.xaml：

<Window x:Class="WpfApp1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"        
        mc:Ignorable="d"
        Title="MainWindow" Height="400" Width="600" Loaded="Window_Loaded">

    <Grid HorizontalAlignment="Stretch" VerticalAlignment="Stretch" >
        <TextBox HorizontalAlignment="Left" Height="210" Margin="10,46,0,0"
                 x:Name="tbFilename"
                 TextWrapping="Wrap" Text="" VerticalAlignment="Top" Width="427"/>
    </Grid>
</Window>

主窗口.xaml.cs

using System;
using System.Collections.Generic;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Runtime.InteropServices;
using System.Windows.Interop;

namespace WpfApp1
{
    public partial class MainWindow : Window
    {                     

        //обработчик сообщений для окна
        private IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
        {
            if (msg == App.WM_COPYDATA)
            {
                App.COPYDATASTRUCT data = new App.COPYDATASTRUCT();
                data = (App.COPYDATASTRUCT)Marshal.PtrToStructure(lParam, data.GetType());
                tbFilename.Text += Marshal.PtrToStringUni(data.lpData)+";";                
            }

            return IntPtr.Zero;
        }

        public MainWindow()
        {
            InitializeComponent();

            string[] argv = Environment.GetCommandLineArgs();
            if (argv.Length > 1)
                tbFilename.Text += argv[1] + ";";            
        }        


        private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            WindowInteropHelper h = new WindowInteropHelper(this);
            HwndSource source = HwndSource.FromHwnd(h.Handle);
            source.AddHook(new HwndSourceHook(WndProc));//регистрируем обработчик сообщений            
        }
    }
}