Windows File & Folder Picker DLL

This repository provides a native Windows DLL that exposes three exported functions for use in Windows applications (including Unity and other .NET projects). These functions allow opening native file and folder selection dialogs with Unicode support and customizable initial directories.

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Download DLL

• Download From Releases - https://github.com/vinayak-vc/WindowsFileDialogDLL/releases

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Features

• Open a standard file open dialog for any file.
• Open a filtered file open dialog with specific extensions.
• Open a folder selection dialog.
• Full Unicode (wchar_t) support.
• Optionally set the initial directory when dialogs open.
• Safe string handling: returned paths remain valid until the next call.
• Restores current working directory after dialog use.

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Exported Functions

1. OpenWindowsFile

extern "C" __declspec(dllexport) const wchar_t* OpenWindowsFile(const wchar_t* initialDir = NULL);

Opens a native Windows file open dialog allowing selection of any file.

• Parameters:
  • initialDir (optional): Initial directory path. Pass NULL to use default.
• Returns: Full path of the selected file, or an empty string if cancelled.

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2. OpenFileWithExtension

extern "C" __declspec(dllexport) const wchar_t* OpenFileWithExtension(const wchar_t* filter, const wchar_t* initialDir = NULL);

Opens a file dialog filtered by file types.

• Parameters:
  • filter: Windows filter string (e.g., L"Text files\0*.txt\0All files\0*.*\0").
  • initialDir (optional): Initial directory path.
• Returns: Full path of the selected file, or empty string if cancelled.

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3. OpenFolderDialog

extern "C" __declspec(dllexport) const wchar_t* OpenFolderDialog(const wchar_t* initialDir = NULL);

Opens a folder selection dialog.

• Parameters:
  • initialDir (optional): Initial folder path.
• Returns: Full path of the selected folder, or empty string if cancelled.

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Implementation Details

• Uses Win32 APIs (GetOpenFileNameW) for file dialogs.
• Uses COM-based IFileDialog for modern folder picking.
• Initializes and uninitializes COM internally.
• Returned strings are static buffers. Copy them if you need long-term storage.
• Saves and restores the current working directory to avoid side effects.

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Example Usage (C++)

#include <iostream>
#include <windows.h>

int main() {
    const wchar_t* selectedFile = OpenWindowsFile(L"C:\\");
    wprintf(L"Selected file: %s\n", selectedFile);

    const wchar_t* filter = L"Text files\0*.txt\0All files\0*.*\0";
    selectedFile = OpenFileWithExtension(filter, L"C:\\Users\\");
    wprintf(L"Selected filtered file: %s\n", selectedFile);

    const wchar_t* selectedFolder = OpenFolderDialog(L"C:\\");
    wprintf(L"Selected folder: %s\n", selectedFolder);

    return 0;
}

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Build Instructions

1. Install the Windows SDK.
2. Link against:
   • Comdlg32.lib
   • Ole32.lib
3. Compile as a DLL exporting the functions.

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Unity / C# Integration

You can use the DLL inside Unity or other .NET projects via DllImport.

FileExplorer.cs Wrapper

using System;
using System.Runtime.InteropServices;

public static class FileExplorer {
    private const string WindowsFileDialog = "WindowsFileDialog.dll";

    [DllImport(WindowsFileDialog, CharSet = CharSet.Unicode)]
    private static extern IntPtr OpenWindowsFile(string initialDir);

    [DllImport(WindowsFileDialog, CharSet = CharSet.Unicode)]
    private static extern IntPtr OpenFileWithExtension(string filter, string initialDir);

    [DllImport(WindowsFileDialog, CharSet = CharSet.Unicode)]
    private static extern IntPtr OpenFolderDialog(string initialDir);

    public static string OpenFileExplorer(string initialDir = null) {
        IntPtr ptr = OpenWindowsFile(initialDir);
        return Marshal.PtrToStringUni(ptr);
    }

    public static string OpenFileExplorer(string filter, string initialDir = null) {
        IntPtr ptr = OpenFileWithExtension(filter, initialDir);
        return Marshal.PtrToStringUni(ptr);
    }

    public static string OpenFolder(string initialDir = null) {
        IntPtr ptr = OpenFolderDialog(initialDir);
        return Marshal.PtrToStringUni(ptr);
    }
}

Usage in Unity

// Open any file
string file1 = FileExplorer.OpenFileExplorer();
Debug.Log("Selected file: " + file1);

// Open file dialog with filter
string filter = "Text files\0*.txt\0Images\0*.png;*.jpg\0All files\0*.*\0";
string file2 = FileExplorer.OpenFileExplorer(filter, @"C:\\Users\\Public\\Documents");
Debug.Log("Filtered file: " + file2);

// Open folder
string folder = FileExplorer.OpenFolder(@"C:\\Projects");
Debug.Log("Selected folder: " + folder);

Notes

• Place the DLL inside Unity's Plugins folder.
• Works on Windows Editor and Windows builds only.
• Returned string is "" if user cancels.
• Always use correct Windows filter strings (double-null terminated).

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License

This code is provided as-is, free to use and modify without warranty.