The core ClickOnce deployment architecture is based on two XML manifest files: an application manifest and a deployment manifest. The files are used to describe where the ClickOnce applications are installed from, how they are updated, and when they are updated.
Publishing ClickOnce Applications
The application manifest describes the application itself. This includes the assemblies, the dependencies and files that make up the application, the required permissions, and the location where updates will be available. The application developer authors the application manifest by using the Publish Wizard in Visual Studio or the Manifest Generation and Editing Tool (Mage.exe) in the Windows Software Development Kit (SDK). For more information, see How to: Publish a ClickOnce Application using the Publish Wizard.
The deployment manifest describes how the application is deployed. This includes the location of the application manifest, and the version of the application that clients should run.
Deploying ClickOnce Applications
After it is created, the deployment manifest is copied to the deployment location. This can be a Web server, network file share, or media such as a CD. The application manifest and all the application files are also copied to a deployment location that is specified in the deployment manifest. This can be the same as the deployment location, or it can be a different location. When using the Publish Wizard in Visual Studio, the copy operations are performed automatically.
Installing ClickOnce Applications
After it is deployed to the deployment location, end users can download and install the application by clicking an icon representing the deployment manifest file on a Web page or in a folder. In most cases, the end user is presented with a simple dialog box asking the user to confirm installation, after which installation proceeds and the application is started without additional intervention. In cases where the application requires elevated permissions or if the application is not signed by a trusted certificate, the dialog box also asks the user to grant permission before the installation can continue. Though ClickOnce installs are per-user, permission elevation may be required if there are prerequisites that require administrator privileges. For more information about elevated permissions, see Securing ClickOnce Applications.
Certificates can be trusted at the machine or enterprise level, so that ClickOnce applications signed with a trusted certificate can install silently. For more information about trusted certificates, see Trusted Application Deployment Overview.
The application can be added to the user’s Start menu and to the Add or Remove Programs group in the >Control Panel. Unlike other deployment technologies, nothing is added to the Program Files folder or the registry, and no administrative rights are required for installation
Note: It is also possible to prevent the application from being added to the Start menu and Add or Remove Programs group, in effect making it behave like a Web application. For more information, see Choosing a ClickOnce Deployment Strategy.
Updating ClickOnce Applications
When the application developers create an updated version of the application, they generate a new application manifest and copy files to a deployment location—usually a sibling folder to the original application deployment folder. The administrator updates the deployment manifest to point to the location of the new version of the application.
Note: Publish Wizard in Visual Studio can be used to perform these steps.
In addition to the deployment location, the deployment manifest also contains an update location (a Web page or network file share) where the application checks for updated versions. ClickOnce Publish properties are used to specify when and how often the application should check for updates. Update behavior can be specified in the deployment manifest, or it can be presented as user choices in the application’s user interface by means of the ClickOnce APIs. In addition, Publish properties can be employed to make updates mandatory or to roll back to an earlier version. For more information, see Choosing a ClickOnce Update Strategy.
Third Party Installers
You can customize your ClickOnce installer to install third-party components along with your application. You must have the redistributable package (.exe or .msi file) and describe the package with a language-neutral product manifest and a language-specific package manifest. For more information, see Creating Bootstrapper Packages.