can not get folder?

Question

var folder = new FolderPicker();  
  
            var path = await folder.PickSingleFolderAsync();  

it is not work.

Answer 1

Hello,

Welcome to Microsoft Q&A!

The FileOpenPicker, FileSavePicker, and FolderPicker APIs require an HWND associated with them so that they know which window is the target window they need to show over. If you are trying to use FolderPicker in a WinUI3 application, you will need to get the current HWND and set the HWND on the picker.

Like this:

        var Picker = new FolderPicker();  

        // Get the current window's HWND by passing in the Window object  
        var hwnd = WinRT.Interop.WindowNative.GetWindowHandle(this);  

        // Associate the HWND with the file picker  
        WinRT.Interop.InitializeWithWindow.Initialize(Picker, hwnd);  

        Picker.FileTypeFilter.Add("*");  

        var folder = await Picker.PickSingleFolderAsync();  

Thank you.

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Answer 2

For anyone who may be trying to use FolderPicker after calling InitializeWithWindow (as I was) and is still getting an exception:

You MUST set a FileTypeFilter as shown above or the FolderPicker will throw an exception. I'm assuming this is a bug as it's not documented as a property that must be set (and the exception type would be something better if it were by design).

Note: for a C# WinUI3 app (not packaged) - WindowsAppSDK 1.2.221209.1