CustomDialogBox — WPF File Open Dialog

A drop-in replacement for OpenFileDialog in WPF/.NET Framework apps. Explorer-style dual-pane browser — tree on the left, file list on the right — with full MVVM architecture, real-time search, multi-selection, and Shell thumbnails for images.

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Features

Navigation

• Breadcrumb bar — click any segment to jump up, or click the bar to type a path directly (Alt+D)
• Quick Access panel — Bureau, Documents, Images, Musique, Vidéos, Profil from known Windows folders
• Lazy-loaded TreeView — async enumeration, expand-on-first-open with sentinel pattern
• Keyboard shortcuts — F5 refresh, Backspace up, Alt+D address bar, Ctrl+F search, Enter confirm, Escape cancel

File Listing

• Real-time search — Ctrl+F to focus the search box, 200 ms debounce, Escape to clear
• Multi-selection — Ctrl+click, Shift+click; file bar shows count when multiple files are selected
• 4-column ListView — Name (with Shell icon), Type, Size (KB), Date Modified
• Column sorting — click any header, click again to reverse
• UI virtualization — VirtualizingStackPanel in Recycling mode; handles 10 000+ files without a freeze

Shell Integration

• Shell icons — SHGetFileInfo with extension-keyed cache; same icons as Windows Explorer
• Thumbnails for images — IShellItemImageFactory via P/Invoke for .jpg/.jpeg/.png/.gif/.bmp/.webp/.tiff; uses Windows thumbnail cache, async load, falls back to Shell icon
• Reparse point filtering — symlinks and junctions excluded from the tree and list
• Network drives hidden by default — avoids accidental hangs on unreachable UNC paths

Architecture

• Full MVVM — OpenViewModel, FileSystemNodeViewModel, IFileSystemProvider
• IFileSystemProvider abstraction — inject a test double for unit tests, or a VFS/cloud backend
• Async everywhere — Task.Run + CancellationToken for all disk I/O; UI never blocks
• Robust error handling — UnauthorizedAccess, PathTooLong, USB hot-unplug, all handled gracefully

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Quick Start

Single file selection (drop-in replacement)

using CustomDialogBox;

var dialog = new Open { Owner = this };
if (dialog.ShowDialog() == true)
{
    string path = dialog.SelectedPath;  // full path of the selected file
}

Multi-file selection

var dialog = new Open { Owner = this };
if (dialog.ShowDialog() == true)
{
    IReadOnlyList<string> paths = dialog.SelectedPaths;  // all selected files
    string first = dialog.SelectedPath;                   // first (or only) selection
}

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Build

Note: This project targets .NET Framework 4.7.2. Use MSBuild from Visual Studio 2022, not dotnet build (the .NET SDK refuses to build old-style .csproj WPF projects).

# From a Developer Command Prompt for VS 2022
MSBuild CustomDialogBox\CustomDialogBox.csproj /t:Build /p:Configuration=Release

Output lands in CustomDialogBox\bin\Release\CustomDialogBox.exe.

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Requirements

OS	Windows 10 / 11
.NET Framework	4.7.2 or later
UI framework	WPF
Build tool	MSBuild (Visual Studio 2022)

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Architecture

CustomDialogBox/
│
├── IFileSystemProvider.cs          # Abstraction — inject test doubles or VFS backends
├── WindowsFileSystemProvider.cs    # Default: wraps FileSystemService + DriveInfo
│
├── FileSystemNodeViewModel.cs      # Tree node — lazy load, async icons/thumbnails, INotifyPropertyChanged
├── FileSystemService.cs            # Static enumeration — EnumerateDirectories/Files, all exception handling
├── ShellIcons.cs                   # SHGetFileInfo (16×16 icons) + IShellItemImageFactory (thumbnails)
│
├── OpenViewModel.cs                # Dialog state — drives, current list, search, selection, breadcrumbs
├── NavItem.cs                      # Immutable data item for breadcrumb segments and Quick Access entries
├── RelayCommand.cs                 # ICommand wrappers (generic + non-generic)
│
├── Open.xaml                       # Dialog layout — breadcrumb, Quick Access, TreeView, ListView
└── Open.xaml.cs                    # Thin code-behind — routes events to VM, handles keyboard and address bar

Key design decisions

Decision	Rationale
Sentinel child node	TreeView shows expand arrow before enumeration; replace on first expand
async void LoadChildrenAsync()	Fire-and-forget is intentional — UI should not await tree expansion
CancellationToken per node	Rapid expand/collapse does not accumulate background tasks
Filter via CollectionViewSource	Sort and filter share one ICollectionView; no data duplication
IFileSystemProvider	Makes OpenViewModel unit-testable without touching the real file system
Thumbnails lazy-loaded	32×32 thumbnails via Windows thumbnail cache; falls back to Shell icon without a performance penalty

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Extending

Custom file system backend (VFS, cloud, ZIP)

public class MyCloudProvider : IFileSystemProvider
{
    public FileSystemNodeViewModel[] GetChildren(string path, CancellationToken ct = default)
    {
        // query your API, return nodes
    }

    public DriveInfo[] GetDrives() => DriveInfo.GetDrives();
}

// Inject at construction
var dialog = new Open(new MyCloudProvider()) { Owner = this };

The Open window's constructor passes the provider through to OpenViewModel. You will need to expose a public Open(IFileSystemProvider provider) overload — currently the constructor is parameterless but the underlying ViewModel already accepts the provider.

File validation before Ouvrir fires

Override BtnOpen_Click in a subclass or subscribe to Closing to add your own guards (MIME check, size limit, signature verification, etc.). SelectedPaths gives you the full list before the dialog closes.

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Keyboard Reference

Key	Action
Enter	Confirm selection (Ouvrir)
Escape	Cancel / close address bar edit
F5	Refresh current directory
Backspace	Navigate to parent directory
Alt+D	Focus address bar (type a path directly)
Ctrl+F	Focus search box
Ctrl+click	Add to selection (multi-select)
Shift+click	Range selection
Double-click file	Confirm selection
Double-click folder	Navigate into folder

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Roadmap

• .NET 6 / 8 project target (SDK-style .csproj, WPF on modern .NET)
• IFileValidator composable — max size, magic bytes, date range
• File content preview pane (text, image, PDF first page)
• Pinned favorites in Quick Access (persist to %APPDATA%)
• NuGet package (pending API surface review)

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Contributing

Issues and PRs are welcome.

• Shell interop belongs in ShellIcons.cs, not in ViewModels
• Any disk I/O must be off the UI thread (Task.Run + CancellationToken)
• Code style: no var for non-obvious types, no regions, no XML doc on obvious members

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License

MIT — see LICENSE. Ship it, fork it, teach with it.