/// <summary>
/// Implementation for picking a file on UWP platform.
/// </summary>
/// <param name="allowedTypes">
/// Specifies one or multiple allowed types. When null, all file types
/// can be selected while picking.
/// On UWP, specify a list of extensions, like this: ".jpg", ".png".
/// </param>
/// <returns>
/// File data object, or null when user cancelled picking file
/// </returns>
private static async Task <FileResult> PickFileAsync(string[] allowedTypes = null)
{
var picker = new Windows.Storage.Pickers.FileOpenPicker
{
ViewMode = Windows.Storage.Pickers.PickerViewMode.List,
SuggestedStartLocation = Windows.Storage.Pickers.PickerLocationId.DocumentsLibrary
};
var hwnd = Window.Current.CoreWindow.As <IWindowNative>().WindowHandle;
var initializeWithWindow = picker.As <IInitializeWithWindow>();
initializeWithWindow.Initialize(hwnd);
if (allowedTypes is not null)
{
var hasAtleastOneType = false;
foreach (var type in allowedTypes.Where(q => q.StartsWith(".")))
{
picker.FileTypeFilter.Add(type);
hasAtleastOneType = true;
}
if (!hasAtleastOneType)
{
picker.FileTypeFilter.Add("*");
}
}
else
{
picker.FileTypeFilter.Add("*");
}
if (await picker.PickSingleFileAsync() is StorageFile file)
{
StorageApplicationPermissions.FutureAccessList.Add(file);
return(new FileResult(
file.Path,
file.Name,
() => file.OpenStreamForReadAsync().GetAwaiter().GetResult()));
}
return(null);
}