SyncBox for Windows 10 Mobile

A standalone, native C#/XAML UWP Dropbox client for Windows 10 Mobile / UAP 10.0.15063.0. The solution defaults to the ARM platform. It has no WebView and no Dropbox SDK dependency.

Important: use your own Dropbox developer test token

This repository deliberately contains no Dropbox app key, app secret, redirect URI owned by somebody else, or access token. To connect the distributed Windows 10 Mobile package:

1. In the Dropbox App Console for an app you control, enable files.metadata.read and files.content.read, then generate an access token for your personal test account. Also enable files.content.write to upload, create folders, or delete items.
2. Deploy the app, open Add developer test token, paste the token, and choose Save test token.
3. The app returns directly to the main screen and loads your Dropbox.

The app encrypts this token at rest with DataProtectionProvider and, when Windows Credential Locker is available, stores an opt-in copy there so it survives uninstall/reinstall for the same Windows user and package identity. If Credential Locker is unavailable, SyncBox still saves the token securely for normal use and explains that it must be entered again after reinstalling. It does not log the token. This is for developer testing only; Sign out removes both copies. Dropbox does not support OAuth device codes, password grants, or exchanging MFA codes for API tokens.

Camera uploads

Turn on Settings → Automatically upload new camera photos after connecting Dropbox. The app uploads new .jpg, .jpeg, .png, and .heic files from the device Pictures library to /Camera Uploads, records successfully uploaded local files to prevent repeat uploads, and immediately runs an initial scan. It registers a native UWP 15-minute background timer with an Internet-available condition for subsequent scans.

Background work is controlled by Windows 10 Mobile and may be delayed for battery, data-saver, or system resource policies; it is not a guaranteed immediate upload trigger. Turn the switch off to unregister the task. The app needs the Pictures Library capability and only uploads after the user explicitly enables this setting.

Features

• Unauthenticated, loading, error, empty-folder, and authenticated phone-oriented UI states.
• Developer test-token sign-in through native paste controls with protected local storage and Credential Locker persistence.
• Direct Dropbox v2 requests for oauth2/authorize, oauth2/token, files/list_folder, files/list_folder/continue, files/download, files/upload, files/create_folder_v2, and files/delete_v2.
• Folder navigation, folder creation, picker-based upload, and picker-based download followed by Windows file launch.
• File sorting: choose newest to oldest, filename A-Z, or filename Z-A for the current folder. Folders remain grouped before files.
• Lightweight native-glyph command strip at the bottom of the file browser for Back, Refresh, and New folder actions. Back returns to the previous app page when one exists; otherwise it moves up one Dropbox folder and never closes the app.
• Native image thumbnails and preview: supported Dropbox images load compact thumbnails directly in the file list; tap .jpg, .jpeg, .png, .heic, or .gif files for the full native preview. Full previews use a Dropbox thumbnail first and fall back to the original file when needed.
• Native document preview: tap .txt, .rtf, or .docx files to view them inside SyncBox. DOCX previews show document text; RTF uses the native rich-text control. Legacy .doc files open through an installed native document app because UWP has no in-app legacy Word renderer.
• Multi-select image download: choose Select, select one or more image files, then choose Download to save them together to a folder selected through the native picker. The same selection mode can delete selected folders and image files after confirmation.

Build and package for ARM

Open DropboxMobile.sln in Visual Studio with the Universal Windows Platform development and Windows 10 SDK (10.0.15063.0) components installed. Select Release and ARM, then build or deploy to a Windows 10 Mobile device.

From a Developer Command Prompt, the equivalent package command is:

MSBuild.exe DropboxMobile.sln /restore /t:Build /p:Configuration=Release /p:Platform=ARM /p:GenerateAppxPackageOnBuild=true /p:UapAppxPackageBuildMode=SideloadOnly /p:AppxBundle=Never /p:AppxPackageDir=artifacts\ARM\

The published sideload layout is under artifacts\ARM\. The current test package is signed with the self-signed artifacts\ARM\DropboxMobile-Test.cer certificate, whose subject matches the manifest publisher (CN=Developer). To install the test package:

1. Enable Developer Mode on the test device.
2. Trust DropboxMobile-Test.cer for the current user (the included Add-AppDevPackage.ps1 does this automatically on Windows; use your device-management or Device Portal certificate flow for Windows Mobile).
3. Install DropboxMobile_1.0.1.0_ARM.appx together with the ARM-only dependencies in Dependencies\ARM, or run Add-AppDevPackage.ps1.

The test certificate is not a production signing identity. Replace it with a certificate controlled by your organization for any non-test distribution. The published build artifact is ARM-only; no x86/x64 package is created.

Versioning

The next package begins at 1.0.1.0. For subsequent builds, increment the final revision through 1.0.1.10; then increment the build component and reset the revision, producing 1.0.2.0.

If the package installs but does not open, confirm that both Microsoft.NET.CoreRuntime.1.1.appx and Microsoft.VCLibs.ARM.14.00.appx from Dependencies\ARM were installed on the phone. Do not install the main .appx alone.

To package outside Visual Studio, a signing certificate must be configured for the package. The project intentionally does not contain a signing key. Visual Studio can generate a local test certificate for Debug deployment; use an organization-controlled certificate for Release distribution.

Security model and limitations

• The app never asks for or sends a Dropbox app secret. Developer test tokens are protected with the current Windows user context and mirrored to Credential Locker only for reinstall persistence.
• The implementation does not log tokens, HTTP authorization headers, or file contents. All Dropbox traffic is HTTPS.
• This is a prototype, not a full Dropbox sync engine. It has no general background sync, conflict resolution, offline cache, sharing UI, rename, or resumable/chunked uploads. Large uploads are subject to Dropbox's single-request upload limit and memory/network constraints.
• Downloading uses a user-selected save destination. Windows only opens the saved file if a compatible installed handler exists.

Layout

Path	Purpose
DropboxMobile\	UWP application, manifest, XAML, C#, and image assets
DropboxMobile\Services\DropboxAuthService.cs	Protected developer-token session integration and PKCE support for source integration
DropboxMobile\Services\DropboxApiClient.cs	Direct Dropbox v2 HTTP client
artifacts\ARM\	Generated ARM sideload package layout (when package signing/tooling is available)