FileExplorer.cs

/// copy from 
/// https://github.com/heku/Kool.VsDiff/blob/main/Kool.VsDiff.Shared/Models/VS.cs

using EnvDTE;
using Microsoft.VisualStudio;
using Microsoft.VisualStudio.Shell;
using Microsoft.VisualStudio.Shell.Interop;
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Runtime.InteropServices;

using static FileUtil.FileUtilPackage;

namespace FileUtil
{
    public static class SolutionExplorer
    {
        private static readonly string SystemDirectorySeparator = Path.DirectorySeparatorChar.ToString();

        public static string TryGetSingleSelectedFile()
        {
            ThreadHelper.ThrowIfNotOnUIThread();
            try
            {
                var selectedItems = Dte.SelectedItems;
                if (selectedItems.Count < 1)
                {
                    return "";
                }

                var files = GetSelectedFiles(selectedItems);
                if (files?.Count == 1)
                {
                    return files[0].File;
                }
            }
            catch (Exception)
            {
            }
            return "";
        }

        public static bool TryGetSelectedFiles(out string name1, out string name2, out string file1, out string file2)
        {
            ThreadHelper.ThrowIfNotOnUIThread();
            name1 = name2 = file1 = file2 = null;
            try
            {
                var selectedItems = Dte.SelectedItems;
                if (selectedItems.Count != 2)
                {
                    return false;
                }

                var files = GetSelectedFiles(selectedItems);
                if (files?.Count == 2)
                {
                    name1 = files[0].Name;
                    file1 = files[0].File;
                    name2 = files[1].Name;
                    file2 = files[1].File;
                    return !string.IsNullOrEmpty(file1) && !string.IsNullOrEmpty(file2);
                }
            }
            catch (Exception ex)
            {
                Debug.WriteLine($"Failed to get selected files: {ex.Message}.");
            }

            return false;
        }

        private struct NameFile
        {
            public string Name;
            public string File;
        }

        private static List<NameFile> GetSelectedFiles(SelectedItems selectedItems)
        {
            ThreadHelper.ThrowIfNotOnUIThread();
            List<NameFile> files = null;
            foreach (SelectedItem item in selectedItems)
            {
                // The index of file names from 1 to FileCount for the project item
                // https://docs.microsoft.com/en-us/dotnet/api/envdte.projectitem.filenames?redirectedfrom=MSDN&view=visualstudiosdk-2017#EnvDTE_ProjectItem_FileNames_System_Int16_
                var file = item.ProjectItem?.FileNames[1];  // Not works for Folder View
                if (file == null || file.EndsWith(SystemDirectorySeparator))
                {
                    continue;
                }
                files = files ?? new List<NameFile>();
                files.Add(new NameFile { Name = item.ProjectItem.Name, File = file });
            }
            return files ?? GetSelectedFilesInsideFolderView();
        }

        private static List<NameFile> GetSelectedFilesInsideFolderView()
        {
            ThreadHelper.ThrowIfNotOnUIThread();
            var hierarchyPtr = IntPtr.Zero;
            var containerPtr = IntPtr.Zero;
            try
            {
                if (MonitorSelection != null &&
                    MonitorSelection.GetCurrentSelection(out hierarchyPtr, out var itemid, out var multiSelect, out containerPtr) == VSConstants.S_OK)
                {
                    var files = new List<NameFile>();
                    if (itemid != VSConstants.VSITEMID_SELECTION)
                    {
                        if (itemid != VSConstants.VSCOOKIE_NIL &&
                            hierarchyPtr != IntPtr.Zero &&
                            Marshal.GetObjectForIUnknown(hierarchyPtr) is IVsHierarchy hierarchy &&
                            TryGetFile(hierarchy, itemid, out var file))
                        {
                            files.Add(new NameFile { File = file });
                        }
                    }
                    else if (multiSelect != null)
                    {
                        if (multiSelect.GetSelectionInfo(out var numberOfSelectedItems, out _) == VSConstants.S_OK &&
                            numberOfSelectedItems == 2)
                        {
                            var vsItemSelections = new VSITEMSELECTION[numberOfSelectedItems];
                            if (multiSelect.GetSelectedItems(0, numberOfSelectedItems, vsItemSelections) == VSConstants.S_OK)
                            {
                                foreach (var selection in vsItemSelections)
                                {
                                    if (TryGetFile(selection.pHier, selection.itemid, out var file))
                                    {
                                        files.Add(new NameFile { File = file });
                                    }
                                }
                            }
                        }
                    }
                    return files;
                }
                return null;
            }
            finally
            {
                if (hierarchyPtr != IntPtr.Zero)
                {
                    Marshal.Release(hierarchyPtr);
                }
                if (containerPtr != IntPtr.Zero)
                {
                    Marshal.Release(containerPtr);
                }
            }
        }

        private static bool TryGetFile(IVsHierarchy hierarchy, uint itemid, out string file)
        {
            ThreadHelper.ThrowIfNotOnUIThread();
            if (hierarchy != null && hierarchy.GetCanonicalName(itemid, out file) == VSConstants.S_OK && file != null)
            {
                return true;
            }
            file = null;
            return false;
        }
    }
}