set filename for both open file and open folder dialogs (#14308)

samples/ControlCatalog/Pages/DialogsPage.xaml.cs

@@ -222,6 +222,7 @@ namespace ControlCatalog.Pages
                 {
                     Title = "Open file",
                     FileTypeFilter = GetFileTypes(),
+                    SuggestedFileName = "FileName",
                     SuggestedStartLocation = lastSelectedDirectory,
                     AllowMultiple = openMultiple.IsChecked == true
                 });
@@ -264,6 +265,7 @@ namespace ControlCatalog.Pages
                 {
                     Title = "Folder file",
                     SuggestedStartLocation = lastSelectedDirectory,
+                    SuggestedFileName = "FileName",
                     AllowMultiple = openMultiple.IsChecked == true
                 });
 

src/Avalonia.Base/Platform/Storage/FilePickerSaveOptions.cs

@@ -7,11 +7,6 @@ namespace Avalonia.Platform.Storage;
 /// </summary>
 public class FilePickerSaveOptions : PickerOptions
 {
-    /// <summary>
-    /// Gets or sets the file name that the file save picker suggests to the user.
-    /// </summary>
-    public string? SuggestedFileName { get; set; }
-
     /// <summary>
     /// Gets or sets the default extension to be used to save the file.
     /// </summary>

src/Avalonia.Base/Platform/Storage/PickerOptions.cs

@@ -1,4 +1,7 @@
-namespace Avalonia.Platform.Storage;
+using System.Collections.Generic;
+using Avalonia.Platform.Storage;
+
+namespace Avalonia.Platform.Storage;
 
 /// <summary>
 /// Common options for <see cref="IStorageProvider.OpenFolderPickerAsync"/>, <see cref="IStorageProvider.OpenFilePickerAsync"/> and <see cref="IStorageProvider.SaveFilePickerAsync"/> methods. 
@@ -16,4 +19,9 @@ public class PickerOptions
     /// or <see cref="IStorageProvider.TryGetWellKnownFolderAsync"/>.
     /// </summary>
     public IStorageFolder? SuggestedStartLocation { get; set; }
+
+    /// <summary>
+    /// Gets or sets the file name that the file picker suggests to the user.
+    /// </summary>
+    public string? SuggestedFileName { get; set; }
 }

src/Avalonia.Native/SystemDialogs.cs

@@ -41,7 +41,7 @@ namespace Avalonia.Native
                                     options.AllowMultiple.AsComBool(),
                                     options.Title ?? string.Empty,
                                     suggestedDirectory,
-                                    string.Empty,
+                                    options.SuggestedFileName ?? string.Empty,
                                     fileTypes);
 
             var result = await events.Task.ConfigureAwait(false);

src/Windows/Avalonia.Win32/Win32StorageProvider.cs

@@ -39,7 +39,7 @@ namespace Avalonia.Win32
             return await ShowFilePicker(
                 true, true,
                 options.AllowMultiple, false,
-                options.Title, null, options.SuggestedStartLocation, null, null,
+                options.Title, options.SuggestedFileName, options.SuggestedStartLocation, null, null,
                 f => new BclStorageFolder(new DirectoryInfo(f)))
                 .ConfigureAwait(false);
         }
@@ -49,7 +49,7 @@ namespace Avalonia.Win32
             return await ShowFilePicker(
                 true, false,
                 options.AllowMultiple, false,
-                options.Title, null, options.SuggestedStartLocation,
+                options.Title, options.SuggestedFileName, options.SuggestedStartLocation,
                 null, options.FileTypeFilter,
                 f => new BclStorageFile(new FileInfo(f)))
                 .ConfigureAwait(false);