ClickOnce

Description

ClickOnce aims to ease deployment of Windows applications while addressing three issues in conventional models: difficulty updating deployed applications, impact on the user's computer, and the need for administrator permissions. Applications deployed via ClickOnce are installed per user, not per machine, and do not require administrator privileges. Each application is isolated from others, preventing one from breaking another. Code Access Security (CAS) restricts system functions for web-deployed ClickOnce applications to protect data and the client system.

Applications

ClickOnce supports both installed applications, which integrate with the Start Menu, and online applications that run cached in a browser without installation. Deployment can occur from an internet location, a network share, or a local file source such as a CD-ROM. The technology is integrated into Visual Studio 2005 and later, and is natively supported by MSBuild.

Manifests

Two XML manifest files control ClickOnce deployments: a deployment manifest and an application manifest, both using the same XML format as the side-by-side assembly implementation. The deployment manifest (.application) describes the deployment model, including current version, update behavior, and publisher identity with a digital signature; it is intended for administrators. The application manifest (.exe.manifest) describes application assemblies, dependent libraries, and required permissions; it is intended for developers. A user launches a ClickOnce application by clicking its deployment manifest file. Launching only succeeds if the URL is opened via Internet Explorer or Edge; if opened from Outlook, Word, or Excel, the default browser must be Internet Explorer or Edge.

Browser support

Native ClickOnce support is available only through Internet Explorer and Edge. With .NET Framework 3.5 Service Pack 1, Microsoft released a Firefox add-on called .NET Framework Assistant that enabled ClickOnce support in Firefox 3 and later. The initial release had an issue preventing normal uninstallation, which was addressed in a May 2009 update; later versions included with Windows 7 and .NET Framework 4 did not have this problem. Third-party extensions, such as Menarva Ltd's ClickOnce for Google Chrome, add support for other browsers.

Did You Know?

• ClickOnce applications can be self-updating, checking for newer versions and automatically replacing updated files.
• Applications can be configured to check for updates on startup or after startup, and ClickOnce exposes programmatic APIs to customize update behavior.
• Mandatory updates are supported, allowing the entire user base to be moved to a new version in a timely manner.