Merge pull request unoplatform#15572 from unoplatform/dev/mazi/ios-mu…

…ltipick-photos

fix: Use `UIDocumentPickerViewController` if multiple files are picked

doc/articles/features/windows-storage-pickers.md

@@ -2,7 +2,7 @@
 uid: Uno.Features.WSPickers
 ---
 
-# Storage Pickers
+# File and Folder Pickers
 
 > [!TIP]
 > This article covers Uno-specific information for the `Windows.Storage.Pickers` namespace. For a full description of the feature and instructions on using it, see [Windows.Storage.Pickers Namespace](https://learn.microsoft.com/uwp/api/windows.storage.pickers).
@@ -156,6 +156,9 @@ else
 
 > [!NOTE]
 > `SuggestedStartLocation` should be set to prevent crashes on UWP. `FileTypes` must include at least one item. You can add extensions in the format `.extension`, with the exception of `*` (asterisk) which allows picking any type of file.
+>
+> [!NOTE]
+> On iOS, the built-in image picker does not support selection of multiple files. Therefore we fall back to the document picker instead. However, this requires you to specify not only the `SuggestedStartLocation` set to `PicturesLibrary`, but also specifying file type extensions in `FileTypeFilter` (e.g. `.jpg` and `.png`), otherwise OS will not display the Photos app as a file provider in the picker.
 
 ### FileSavePicker
 

src/SamplesApp/UITests.Shared/Windows_Storage/Pickers/FileOpenPickerTests.xaml.cs

@@ -14,7 +14,13 @@
 namespace UITests.Shared.Windows_Storage.Pickers
 {
 	[Sample("Windows.Storage", ViewModelType = typeof(FileOpenPickerTestsViewModel), IsManualTest = true,
-		Description = "Allows testing all features of FileOpenPicker. Currently not supported on Android, iOS, and macOS. Not selecting a file should not cause an exception. Selecting a file should show information below the file picker buttons")]
+		Description =
+"""
+- Not selecting a file should not cause an exception.
+- Selecting a file should show information below the file picker buttons.
+- It should be possible to pick multiple files, even if PicturesLibrary is selected and .jpg is used as file type.
+"""
+	)]
 	public sealed partial class FileOpenPickerTests : Page
 	{
 		public FileOpenPickerTests()

src/Uno.UWP/Storage/Pickers/FileOpenPicker.iOS.cs

@@ -54,7 +54,7 @@ private UIViewController GetViewController(bool multiple, TaskCompletionSource<N
 		{
 			switch (SuggestedStartLocation)
 			{
-				case PickerLocationId.PicturesLibrary:
+				case PickerLocationId.PicturesLibrary when !multiple: // As UIImagePickerController does not support multiple selection, we fall back to UIDocumentPickerViewController for multiple selection
 					return new UIImagePickerController()
 					{
 						SourceType = UIImagePickerControllerSourceType.PhotoLibrary,