Question: Use something to pick files in a WinUI 3 Blank App

[kirilvalev]

I created a WinUI 3 Blank App and I am trying to select a file from the file system. Is there something in Winui 3 to support me doing so, FilePicker and OpenFileDialog do not seem to work with Winui3.

[huoyaoyuan]

They can work with workarounds: #2716 (comment)

[kirilvalev]

@huoyaoyuan, thank you. This only seems to work for WinUI in UWP projects and not for WinUI in Desktop projects.

[huoyaoyuan]

It works for me in WinUI desktop.

[kirilvalev]

Would you please share your .csproj file?

`

WinExe
net5.0-windows10.0.18362.0
10.0.17134.0
TestProjectWinUIDesktop
app.manifest
x86;x64;arm64
win10-x86;win10-x64;win10-arm64

`

[huoyaoyuan]

The project file is unrelated. I'm just using default of preview3.
Where are you calling the picker? It must be called when a window is shown.

[kirilvalev]

Thank you. I am also using WinUI preview 3. New "Blank App, Packaged (WinUI in Desktop)":

`using Microsoft.UI.Xaml;
using Microsoft.UI.Xaml.Controls;
using Microsoft.UI.Xaml.Controls.Primitives;
using Microsoft.UI.Xaml.Data;
using Microsoft.UI.Xaml.Input;
using Microsoft.UI.Xaml.Media;
using Microsoft.UI.Xaml.Navigation;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices.WindowsRuntime;
using Windows.Foundation;
using Windows.Foundation.Collections;

// To learn more about WinUI, the WinUI project structure,
// and more about our project templates, see: http://aka.ms/winui-project-info.

namespace TestProjectWinUIDesktop
{
///

/// An empty window that can be used on its own or navigated to within a Frame.
///

public sealed partial class MainWindow : Window
{
public MainWindow()
{
this.InitializeComponent();
}

    private async void myButton_Click(object sender, RoutedEventArgs e)
    {
        myButton.Content = "Clicked";


        // Open a text file.
        Windows.Storage.Pickers.FileOpenPicker open = new Windows.Storage.Pickers.FileOpenPicker
        {
            SuggestedStartLocation = Windows.Storage.Pickers.PickerLocationId.DocumentsLibrary
        };
        open.FileTypeFilter.Add(".rtf");

        Windows.Storage.StorageFile file = await open.PickSingleFileAsync();

        if (file != null)
        {
            using (Windows.Storage.Streams.IRandomAccessStream randAccStream =
                await file.OpenAsync(Windows.Storage.FileAccessMode.Read))
            {
                // Load the file into the Document property of the RichEditBox.
                // editor.Document.LoadFromStream(Windows.UI.Text.TextSetOptions.FormatRtf, randAccStream);
            }
        }


    }
}

}`

Somehow the code feature in the editor is not formatting my code, sorry for that...

[huoyaoyuan]

You are using the default approach, which doesn't work. You need workaround from this comment: #2716 (comment)

[kirilvalev]

I understand, thank you! I thought, since the ticket #2716 is closed it would work without a workaround.

[marb2000]

Hi there,

In Desktop, or Win32, it's required to specify which Window Handle (HWND) owns the File/Folder Picker. It's the current design. Here you can find a code snipped:

 public sealed partial class MainWindow : Window
    {
        public MainWindow()
        {
            this.InitializeComponent();
        }

        private async void myButton_Click(object sender, RoutedEventArgs e)
        {
            var filePicker = new FileOpenPicker();

            //Get the Window's HWND
            var hwnd = this.As<IWindowNative>().WindowHandle;
       
            //Make folder Picker work in Win32
            var initializeWithWindow = filePicker.As<IInitializeWithWindow>();
            initializeWithWindow.Initialize(hwnd);
      
            filePicker.FileTypeFilter.Add("*");

            var folder = await filePicker.PickSingleFileAsync();
            myText.Text = folder != null ? folder.Path : string.Empty;
        }

        [ComImport]
        [Guid("3E68D4BD-7135-4D10-8018-9FB6D9F33FA1")]
        [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
        public interface IInitializeWithWindow
        {
            void Initialize(IntPtr hwnd);
        }
        [ComImport]
        [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
        [Guid("EECDBF0E-BAE9-4CB6-A68E-9598E1CB57BB")]
        internal interface IWindowNative
        {
            IntPtr WindowHandle { get; }
        }
    }

[marb2000]

Closing the issue. I hope the sample is good enough.

[nickrandolph]

@marb2000 the sample works fine.
A note for anyone trying to get this to work - make sure you add "using WinRT;" to the file where you're adding this code, otherwise you'll get compile issues with the "As" method. Window (as with a lot of WinUI classes) has a static As method, which conflicts with the As extension method available when adding the WinRT namespaces.

@marb2000 general comments/questions:

• This is super ugly to have to do this - is there a plan to clean this up so the developers don't have to deal with this hacky workaround?
• Is there a way to fall back to the UWP file picker when running in partial trust?

[mrjfalk]

I also ran into this issue, and while the workaround works it's not very nice experience and took some time to find this workaround.

As I use pickers in a number of places I wrote an extension method to help with this (usage: picker.SetOwnerWindow(this);), might be useful for others as well: https://gist.github.com/mrjfalk/93f7c66cabce1f68fef7102c38b2505e

[Rybasum]

@marb2000 The only reason I have to stay with UWP is that I want to run in AppContainer. Thanks to @nickrandolph I can run WinUI 3 in AppContainer but attempting to use hWnd with a file open picker leads to an Access Denied exception. Please, could Microsoft provide a way to initialise popup windows without an explicit usage of a hWnd?

[ghostidentity]

Hi, Im not sure why its close. I tried on Winui3 but there's an issue.