The simplest way to create a new XBAP project is with Microsoft Visual Studio:

1. On the File menu, point to New, and then click Project.

2. In the New Project dialog box, in the Project types pane, choose either Visual Basic or Visual C#. In the Templates pane, click WPF Browser Application.

3. Assign a project name and click OK to create the new project.

The WPF Browser Application project template creates an XBAP application project that includes the following:

• An application definition, Application.xaml.

• A page, Page1.xaml.

You can add to those as required.

If you prefer developing with tools that require command-line compilation, see Building a WPF Application (WPF).

When you run an XBAP, it is launched in a browser window instead of a standalone window. When you debug an XBAP from Visual Studio, the application runs with Internet zone permission and will consequently throw security exceptions if those permissions are exceeded. For more information, see Building a WPF Application (WPF).

When you build a XBAP, the Microsoft build engine (MSBuild) produces the following three files as a minimum:

• An executable file. This contains the compiled code and has an .exe extension.

• An application manifest. This contains metadata associated with the application and has a .manifest extension.

• A deployment manifest. This file contains the information that ClickOnce uses to deploy the application and has an .xbap extension.

You publish XBAPs to a Web server (Microsoft Internet Information Services (IIS) or later). You do not need to install .NET Framework on the Web server, but you do need to register the WPF Multipurpose Internet Mail Extensions (MIME) types and file extensions. See How to: Configure IIS 5.0 and IIS 6.0 to Deploy WPF Applications for details.

To prepare your XBAP for deployment, copy the .exe and the associated manifests to your Web server. Create a hyperlink on a Web page to navigate to the deployment manifest. When the user clicks the link and navigates to the .xbap file, ClickOnce automatically handles the mechanics of downloading and launching the application.

Clearing Cached XBAPs

XBAPs must execute within a partial-trust security sandbox that is restricted to the Internet zone permission set. Consequently, your implementation must support the subset of WPF elements that are supported in the Internet zone (see Windows Presentation Foundation Security).

When you host the WebBrowser ActiveX control (WebOC) in the Internet Explorer browser process, the following security limitations apply.

• Internet Explorer blocks modal dialog boxes from the DHTML alert function and ActiveX controls hosted in HTML. Internet Explorer suppresses dialog boxes that originate from threads other than the active tab’s thread.

• Hosting the WebOC control raises an exception when an XBAP is loaded cross-domain in an HTML page.

An important aspect of XBAP performance is its start time. If an XBAP is the first WPF application to load, the cold start time can be ten seconds or more. This is because the progress page is rendered by WPF, and both the CLR and WPF must be cold-started to display it. 

Starting in Visual Studio 2008 SP1, XBAP cold-start time is mitigated by displaying an unmanaged progress page early in the deployment cycle. The progress page appears almost immediately after the application is started, because it is displayed by native hosting code and rendered in HTML. 

In addition, improved concurrency of the ClickOnce download sequence improves the start time by up to ten percent. After ClickOnce downloads and validates manifests, the application download starts, and the progress bar begins to update.