InfiniLore · AnnaSasDev · Aug 3, 2026 · Aug 3, 2026
diff --git a/docs/docs/guides/core-window.md b/docs/docs/guides/core-window.md
@@ -561,7 +561,8 @@ string?[] folders = window.ShowOpenFolder("Select Folder", multiSelect: false);
 string? path = window.ShowSaveFile(
     title: "Save As",
     defaultPath: null,
-    filters: [("Text Files", ["txt"])]
+    filters: [("Text Files", ["txt"])],
+    defaultFileName: "document.txt"
 );
 ```
 

diff --git a/docs/docs/migration/photino-backlog.md b/docs/docs/migration/photino-backlog.md
@@ -81,7 +81,7 @@ This backlog will be used to track any remaining issues or features that need to
 | 📝     | Interoperability between C # and JavaScript                                                   | [Photino.NET#120](https://github.com/tryphotino/photino.NET/issues/120) | [InfiniFrame#294](https://github.com/InfiniLore/InfiniFrame/issues/219)                                                                                                                                             |
 | ✅      | Window.external is deprecated by browsers                                                     | [Photino.NET#124](https://github.com/tryphotino/photino.NET/issues/124) |                                                                                                                                                                                                                     |
 | 📝     | Intercept navigation events                                                                   | [Photino.NET#139](https://github.com/tryphotino/photino.NET/issues/139) | [InfiniFrame#294](https://github.com/InfiniLore/InfiniFrame/issues/294)                                                                                                                                             |
-| 📝     | ShowSaveFile How to set the default file name                                                 | [Photino.NET#140](https://github.com/tryphotino/photino.NET/issues/140) | [InfiniFrame#295](https://github.com/InfiniLore/InfiniFrame/issues/295)                                                                                                                                             |
+| ✅     | ShowSaveFile How to set the default file name                                                 | [Photino.NET#140](https://github.com/tryphotino/photino.NET/issues/140) | [InfiniFrame#295](https://github.com/InfiniLore/InfiniFrame/issues/295)                                                                                                                                             |
 | 📝     | Running as administrator disables other instances                                             | [Photino.NET#162](https://github.com/tryphotino/photino.NET/issues/162) | [InfiniFrame#296](https://github.com/InfiniLore/InfiniFrame/issues/296)                                                                                                                                             |
 | ❌      | Mica/Fluent design window for windows                                                         | [Photino.NET#167](https://github.com/tryphotino/photino.NET/issues/167) |                                                                                                                                                                                                                     |
 | 📝     | Retrieve current Url of PhotinoWindow                                                         | [Photino.NET#197](https://github.com/tryphotino/photino.NET/issues/197) | [InfiniFrame#297](https://github.com/InfiniLore/InfiniFrame/issues/297)                                                                                                                                             |

diff --git a/...rame.Js/TypeScript/Contracts/Window/Features/FilePickerDialogsInfiniFrameWindowFeature.ts b/...rame.Js/TypeScript/Contracts/Window/Features/FilePickerDialogsInfiniFrameWindowFeature.ts
@@ -8,5 +8,5 @@ import type {FilePickerFilter} from "./WindowFeatureTypes";
 export interface FilePickerDialogsInfiniFrameWindowFeature {
     showOpenFileAsync(title?: string, defaultPath?: string | null, multiSelect?: boolean, filters?: FilePickerFilter[] | null): Promise<(string | null)[]>;
     showOpenFolderAsync(title?: string, defaultPath?: string | null, multiSelect?: boolean): Promise<(string | null)[]>;
-    showSaveFileAsync(title?: string, defaultPath?: string | null, filters?: FilePickerFilter[] | null): Promise<string | null>;
+    showSaveFileAsync(title?: string, defaultPath?: string | null, filters?: FilePickerFilter[] | null, defaultFileName?: string | null): Promise<string | null>;
 }
diff --git a/src/InfiniFrame.Js/TypeScript/Window/Features/FilePickerDialogsInfiniFrameWindowFeature.ts b/src/InfiniFrame.Js/TypeScript/Window/Features/FilePickerDialogsInfiniFrameWindowFeature.ts
@@ -17,7 +17,7 @@ export class FilePickerDialogsInfiniFrameWindowFeature extends InfiniFrameWindow
         return this.get<(string | null)[]>("showOpenFolder", {title, defaultPath, multiSelect});
     }
 
-    showSaveFileAsync(title = "Save file", defaultPath: string | null = null, filters: FilePickerFilter[] | null = null) {
-        return this.get<string | null>("showSaveFile", {title, defaultPath, filters});
+    showSaveFileAsync(title = "Save file", defaultPath: string | null = null, filters: FilePickerFilter[] | null = null, defaultFileName: string | null = null) {
+        return this.get<string | null>("showSaveFile", {title, defaultPath, filters, defaultFileName});
     }
 }
diff --git a/src/InfiniFrame.Js/TypeScript/Window/InfiniFrameWindowFeatures.test.ts b/src/InfiniFrame.Js/TypeScript/Window/InfiniFrameWindowFeatures.test.ts
@@ -75,7 +75,8 @@ const contracts: FeatureContract[] = [
         gets: [
             {method: "showOpenFileAsync", command: "showOpenFile", parameters: ["Open", "/tmp", true, [{name: "Text", extensions: ["txt"]}]], args: {title: "Open", defaultPath: "/tmp", multiSelect: true, filters: [{name: "Text", extensions: ["txt"]}]}, result: ["/tmp/a.txt"]},
             {method: "showOpenFolderAsync", command: "showOpenFolder", parameters: ["Folder", "/tmp", true], args: {title: "Folder", defaultPath: "/tmp", multiSelect: true}, result: ["/tmp"]},
-            {method: "showSaveFileAsync", command: "showSaveFile", parameters: ["Save", "/tmp/a.txt", null], args: {title: "Save", defaultPath: "/tmp/a.txt", filters: null}, result: "/tmp/a.txt"}
+            {method: "showSaveFileAsync", command: "showSaveFile", parameters: ["Save", "/tmp/a.txt", null, null], args: {title: "Save", defaultPath: "/tmp/a.txt", filters: null, defaultFileName: null}, result: "/tmp/a.txt"},
+            {method: "showSaveFileAsync", command: "showSaveFile", parameters: ["Save", "/tmp/a.txt", null, "document.txt"], args: {title: "Save", defaultPath: "/tmp/a.txt", filters: null, defaultFileName: "document.txt"}, result: "/tmp/a.txt"}
         ]
     },
     {

diff --git a/...me.Shared/Window/Features/FilePickerDialogs/IFilePickerDialogsInfiniFrameWindowFeature.cs b/...me.Shared/Window/Features/FilePickerDialogs/IFilePickerDialogsInfiniFrameWindowFeature.cs
@@ -52,16 +52,18 @@ public interface IFilePickerDialogsInfiniFrameWindowFeature {
     /// <param name="title">The dialog title.</param>
     /// <param name="defaultPath">The default directory path.</param>
     /// <param name="filters">File extension filters.</param>
+    /// <param name="defaultFileName">The default file name to pre-populate in the save dialog.</param>
     /// <returns>The selected file path, or <c>null</c> if cancelled.</returns>
-    string? ShowSaveFile(string title = "Save file", string? defaultPath = null, (string Name, string[] Extensions)[]? filters = null);
+    string? ShowSaveFile(string title = "Save file", string? defaultPath = null, (string Name, string[] Extensions)[]? filters = null, string? defaultFileName = null);
 
     /// <summary>
     ///     Shows a save file dialog asynchronously and returns the selected file path.
     /// </summary>
     /// <param name="title">The dialog title.</param>
     /// <param name="defaultPath">The default directory path.</param>
     /// <param name="filters">File extension filters.</param>
+    /// <param name="defaultFileName">The default file name to pre-populate in the save dialog.</param>
     /// <param name="ct">Cancellation token.</param>
     /// <returns>A task that resolves to the selected file path, or <c>null</c> if cancelled.</returns>
-    Task<string?> ShowSaveFileAsync(string title = "Choose file", string? defaultPath = null, (string Name, string[] Extensions)[]? filters = null, CancellationToken ct = default);
+    Task<string?> ShowSaveFileAsync(string title = "Choose file", string? defaultPath = null, (string Name, string[] Extensions)[]? filters = null, string? defaultFileName = null, CancellationToken ct = default);
 }
diff --git a/...Window/Features/FilePickerDialogs/IFilePickerDialogsInfiniFrameWindowFeatureExtensions.cs b/...Window/Features/FilePickerDialogs/IFilePickerDialogsInfiniFrameWindowFeatureExtensions.cs
@@ -61,9 +61,10 @@ public static class IFilePickerDialogsInfiniFrameWindowFeatureExtensions {
     /// <param name="title">The dialog title.</param>
     /// <param name="defaultPath">The default directory path.</param>
     /// <param name="filters">File extension filters.</param>
+    /// <param name="defaultFileName">The default file name to pre-populate in the save dialog.</param>
     /// <returns>The selected file path, or <c>null</c> if cancelled.</returns>
-    public static string? ShowSaveFile(this IInfiniFrameWindow window, string title = "Save file", string? defaultPath = null, (string Name, string[] Extensions)[]? filters = null)
-        => window.Features.FilePickerDialogs.ShowSaveFile(title, defaultPath, filters);
+    public static string? ShowSaveFile(this IInfiniFrameWindow window, string title = "Save file", string? defaultPath = null, (string Name, string[] Extensions)[]? filters = null, string? defaultFileName = null)
+        => window.Features.FilePickerDialogs.ShowSaveFile(title, defaultPath, filters, defaultFileName);
 
     /// <summary>
     ///     Shows a save file dialog asynchronously and returns the selected file path.
@@ -72,8 +73,9 @@ public static class IFilePickerDialogsInfiniFrameWindowFeatureExtensions {
     /// <param name="title">The dialog title.</param>
     /// <param name="defaultPath">The default directory path.</param>
     /// <param name="filters">File extension filters.</param>
+    /// <param name="defaultFileName">The default file name to pre-populate in the save dialog.</param>
     /// <param name="ct">Cancellation token.</param>
     /// <returns>A task that resolves to the selected file path, or <c>null</c> if cancelled.</returns>
-    public static Task<string?> ShowSaveFileAsync(this IInfiniFrameWindow window, string title = "Choose file", string? defaultPath = null, (string Name, string[] Extensions)[]? filters = null, CancellationToken ct = default)
-        => window.Features.FilePickerDialogs.ShowSaveFileAsync(title, defaultPath, filters, ct);
+    public static Task<string?> ShowSaveFileAsync(this IInfiniFrameWindow window, string title = "Choose file", string? defaultPath = null, (string Name, string[] Extensions)[]? filters = null, string? defaultFileName = null, CancellationToken ct = default)
+        => window.Features.FilePickerDialogs.ShowSaveFileAsync(title, defaultPath, filters, defaultFileName, ct);
 }
diff --git a/...nfiniFrame/Window/Features/FilePickerDialogs/FilePickerDialogsInfiniFrameWindowFeature.cs b/...nfiniFrame/Window/Features/FilePickerDialogs/FilePickerDialogsInfiniFrameWindowFeature.cs
@@ -26,18 +26,18 @@ ILogger<FilePickerDialogsInfiniFrameWindowFeature> logger
 
     /// <inheritdoc cref="IFilePickerDialogsInfiniFrameWindowFeature.ShowOpenFileAsync" />
     public Task<string?[]> ShowOpenFileAsync(string title = DefaultFilePickerTitle, string? defaultPath = null, bool multiSelect = false, (string Name, string[] Extensions)[]? filters = null, CancellationToken ct = default)
-        => ShowDialogAsync(InfiniFileDialogKind.OpenFile, title, defaultPath, multiSelect, filters, ct);
+        => ShowDialogAsync(InfiniFileDialogKind.OpenFile, title, defaultPath, multiSelect, filters, null, ct);
 
     /// <inheritdoc cref="IFilePickerDialogsInfiniFrameWindowFeature.ShowOpenFolder" />
     public string?[] ShowOpenFolder(string title = DefaultFolderPickerTitle, string? defaultPath = null, bool multiSelect = false)
         => ShowOpenDialog(true, title, defaultPath, multiSelect, null);
 
     /// <inheritdoc cref="IFilePickerDialogsInfiniFrameWindowFeature.ShowOpenFolderAsync" />
     public Task<string?[]> ShowOpenFolderAsync(string title = DefaultFolderPickerTitle, string? defaultPath = null, bool multiSelect = false, CancellationToken ct = default)
-        => ShowDialogAsync(InfiniFileDialogKind.OpenFolder, title, defaultPath, multiSelect, null, ct);
+        => ShowDialogAsync(InfiniFileDialogKind.OpenFolder, title, defaultPath, multiSelect, null, null, ct);
 
     /// <inheritdoc cref="IFilePickerDialogsInfiniFrameWindowFeature.ShowSaveFile" />
-    public string? ShowSaveFile(string title = DefaultSaveFilePickerTitle, string? defaultPath = null, (string Name, string[] Extensions)[]? filters = null) {
+    public string? ShowSaveFile(string title = DefaultSaveFilePickerTitle, string? defaultPath = null, (string Name, string[] Extensions)[]? filters = null, string? defaultFileName = null) {
         if (window.IsClosedOrClosing()) return null;
 
         defaultPath ??= Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);
@@ -54,15 +54,15 @@ ILogger<FilePickerDialogsInfiniFrameWindowFeature> logger
             defaultPath,
             nativeFilters,
             filters.Length,
-            null// TODO actually assign this
+            defaultFileName
         );
 
         return result;
     }
 
     /// <inheritdoc cref="IFilePickerDialogsInfiniFrameWindowFeature.ShowSaveFileAsync" />
-    public Task<string?> ShowSaveFileAsync(string title = DefaultSaveFilePickerTitle, string? defaultPath = null, (string Name, string[] Extensions)[]? filters = null, CancellationToken ct = default)
-        => ShowSaveDialogAsync(title, defaultPath, filters, ct);
+    public Task<string?> ShowSaveFileAsync(string title = DefaultSaveFilePickerTitle, string? defaultPath = null, (string Name, string[] Extensions)[]? filters = null, string? defaultFileName = null, CancellationToken ct = default)
+        => ShowSaveDialogAsync(title, defaultPath, filters, defaultFileName, ct);
 
     private string?[] ShowOpenDialog(bool foldersOnly, string title, string? defaultPath, bool multiSelect, (string Name, string[] Extensions)[]? filters) {
         if (window.IsClosedOrClosing()) return [];
@@ -107,6 +107,7 @@ ILogger<FilePickerDialogsInfiniFrameWindowFeature> logger
         string? defaultPath,
         bool multiSelect,
         (string Name, string[] Extensions)[]? filters,
+        string? defaultFileName,
         CancellationToken ct
     ) {
         ct.ThrowIfCancellationRequested();
@@ -115,7 +116,7 @@ CancellationToken ct
         filters ??= [];
         var operation = new InfiniFileDialogOperation(
             window, logger, kind, title, defaultPath, multiSelect,
-            GetNativeFilters(filters, kind == InfiniFileDialogKind.OpenFolder), ct
+            GetNativeFilters(filters, kind == InfiniFileDialogKind.OpenFolder), defaultFileName, ct
         );
         _ = operation.StartAsync();
         return await operation.Task.WaitAsync(ct).ConfigureAwait(false);
@@ -125,10 +126,11 @@ CancellationToken ct
         string title,
         string? defaultPath,
         (string Name, string[] Extensions)[]? filters,
+        string? defaultFileName,
         CancellationToken ct
     ) {
         string?[] values = await ShowDialogAsync(
-            InfiniFileDialogKind.SaveFile, title, defaultPath, false, filters, ct
+            InfiniFileDialogKind.SaveFile, title, defaultPath, false, filters, defaultFileName, ct
         ).ConfigureAwait(false);
         return values.FirstOrDefault();
     }

diff --git a/src/InfiniFrame/Window/Features/FilePickerDialogs/FilePickerDialogsWebMessageDispatcher.cs b/src/InfiniFrame/Window/Features/FilePickerDialogs/FilePickerDialogsWebMessageDispatcher.cs
@@ -20,11 +20,12 @@ protected override IFilePickerDialogsInfiniFrameWindowFeature SelectFeature(IInf
         string? defaultPath = Arg<string?>(args, "defaultPath", null);
         WindowFeatureFilePickerFilter[]? filterDtos = Arg<WindowFeatureFilePickerFilter[]?>(args, "filters", null);
         (string Name, string[] Extensions)[]? filters = filterDtos?.Select(filter => (filter.Name, filter.Extensions)).ToArray();
+        string? defaultFileName = Arg<string?>(args, "defaultFileName", null);
 
         return command switch {
             "showOpenFile" => feature.ShowOpenFile(Arg(args, "title", "Choose file"), defaultPath, Arg(args, "multiSelect", false), filters),
             "showOpenFolder" => feature.ShowOpenFolder(Arg(args, "title", "Select folder"), defaultPath, Arg(args, "multiSelect", false)),
-            "showSaveFile" => feature.ShowSaveFile(Arg(args, "title", "Save file"), defaultPath, filters),
+            "showSaveFile" => feature.ShowSaveFile(Arg(args, "title", "Save file"), defaultPath, filters, defaultFileName),
             _ => throw Unsupported(command)
         };
     }

diff --git a/src/InfiniFrame/Window/Features/FilePickerDialogs/InfiniFileDialogOperation.cs b/src/InfiniFrame/Window/Features/FilePickerDialogs/InfiniFileDialogOperation.cs
@@ -25,6 +25,7 @@ internal sealed class InfiniFileDialogOperation {
     private readonly string _defaultPath;
     private readonly bool _multiSelect;
     private readonly string[] _filters;
+    private readonly string? _defaultFileName;
     private readonly CancellationToken _cancellationToken;
     private readonly string? _diagnosticKey;
     private readonly TaskCompletionSource<string?[]> _completion =
@@ -48,6 +49,7 @@ public InfiniFileDialogOperation(
         string defaultPath,
         bool multiSelect,
         string[] filters,
+        string? defaultFileName,
         CancellationToken cancellationToken
     ) {
         _window = window;
@@ -57,6 +59,7 @@ CancellationToken cancellationToken
         _defaultPath = defaultPath;
         _multiSelect = multiSelect;
         _filters = filters;
+        _defaultFileName = defaultFileName;
         _cancellationToken = cancellationToken;
         _diagnosticKey = (window as InfiniFrameWindow)?.BeginDiagnosticOperation(kind.ToString(), Id);
     }
@@ -79,7 +82,7 @@ public async Task StartAsync() {
                         _lease.Handle, Id, _title, _defaultPath, _multiSelect, CompletionCallback, context),
                     InfiniFileDialogKind.SaveFile => InfiniFrameNative.BeginShowSaveFile(
                         _lease.Handle, Id, _title, _defaultPath,
-                        _filters, _filters.Length, string.Empty, CompletionCallback, context),
+                        _filters, _filters.Length, _defaultFileName ?? string.Empty, CompletionCallback, context),
                     _ => InfiniFrameNativeInteropStatus.InvalidArgument
                 };
                 if (status != InfiniFrameNativeInteropStatus.Success)

diff --git a/...ts.InfiniFrame/Window/Features/FilePickerDialogs/FilePickerDialogsDefaultFileNameTests.cs b/...ts.InfiniFrame/Window/Features/FilePickerDialogs/FilePickerDialogsDefaultFileNameTests.cs
@@ -0,0 +1,48 @@
+// ---------------------------------------------------------------------------------------------------------------------
+// Imports
+// ---------------------------------------------------------------------------------------------------------------------
+using InfiniFrame;
+
+namespace InfiniTests.InfiniFrame.Window.Features.FilePickerDialogs;
+// ---------------------------------------------------------------------------------------------------------------------
+// Code
+// ---------------------------------------------------------------------------------------------------------------------
+public class FilePickerDialogsDefaultFileNameTests {
+    [Test]
+    [NotInParallelInfiniTests]
+    public async Task ShowSaveFile_WithDefaultFileName_ShouldAcceptParameter(CancellationToken ct) {
+        // Arrange
+        using var windowUtility = InfiniFrameTestWindow.Create(ct);
+        IInfiniFrameWindow window = windowUtility.Window;
+        await EnsureWindowClosed(window, ct);
+
+        // Act
+        string? result = window.Features.FilePickerDialogs.ShowSaveFile(defaultFileName: "document.txt");
+
+        // Assert
+        await Assert.That(result).IsNull();
+    }
+
+    [Test]
+    [NotInParallelInfiniTests]
+    public async Task ShowSaveFile_Extension_WithDefaultFileName_ShouldAcceptParameter(CancellationToken ct) {
+        // Arrange
+        using var windowUtility = InfiniFrameTestWindow.Create(ct);
+        IInfiniFrameWindow window = windowUtility.Window;
+        await EnsureWindowClosed(window, ct);
+
+        // Act
+        string? result = window.ShowSaveFile(defaultFileName: "document.txt");
+
+        // Assert
+        await Assert.That(result).IsNull();
+    }
+
+    private static async Task EnsureWindowClosed(IInfiniFrameWindow window, CancellationToken ct) {
+        window.Close();
+        DateTime timeoutAt = DateTime.UtcNow.AddSeconds(5);
+        while (!window.IsClosedOrClosing() && DateTime.UtcNow < timeoutAt) {
+            await Task.Delay(50, ct);
+        }
+    }
+}