A ClickOnce application will work fine over SSL, except when Internet Explorer raises a prompt about the SSL certificate. The prompt can be raised when there is something wrong with the certificate, such as when the site names do not match or the certificate has expired. To make ClickOnce work over an SSL connection, make sure that the certificate is up-to-date, and that the certificate data matches the site data.

ClickOnce provides support for Windows Integrated proxy authentication. No specific machine.config directives are required. ClickOnce does not provide support for other authentication protocols such as Basic or Digest.

For more information, see <defaultProxy> Element (Network Settings).

Currently, ClickOnce installations will launch only if the URL to the deployment manifest is opened using Internet Explorer. A deployment whose URL is launched from another application, such as Microsoft Office Outlook, will launch successfully only if Internet Explorer is set as the default Web browser.

Note:
Mozilla Firefox is also supported, but only if the deployment provider is not blank, and the ClickOnce plug-in for Firefox is installed.

If you have developed a custom Web page that launches a ClickOnce application using Active Scripting, you may find that the application will not launch on some machines. Internet Explorer contains a setting called Automatic prompting for file downloads, which affects this behavior. This setting is available on the Security Tab in its Options menu that affects this behavior. It is called Automatic prompting for file downloads, and it is listed underneath the Downloads category. The property is set to Enable by default for intranet Web pages, and to Disable by default for Internet Web pages. When this setting is set to Disable, any attempt to activate a ClickOnce application programmatically (for example, by assigning its URL to the document.location property) will be blocked. Under this circumstance, users can launch applications only through a user-initiated download, for example, by clicking a hyperlink set to the application's URL.

If you are deploying a ClickOnce application from a Web server other than IIS, you may experience a problem if the server is returning the incorrect content type for key ClickOnce files, such as the deployment manifest and application manifest. To resolve this problem, see your Web server's Help documentation about how to add new content types to the server, and make sure that all the file name extension mappings listed in the following table are in place.

ClickOnce supports installing applications from any HTTP 1.1 Web server or file server. FTP, the File Transfer Protocol, is not supported for installing applications. You can use FTP to publish applications only. The following table summarizes these differences:

By default, Windows XP SP2 enables the Windows Firewall. If you are developing your application on a computer that has Windows XP installed, you are still able to publish and run ClickOnce applications from the local server that is running IIS. However, you cannot access that server that is running IIS from another computer unless you open the Windows Firewall. See Windows Help for instructions on managing the Windows Firewall.

FrontPage 2002 Server Extensions from Microsoft is required for publishing applications to a Windows Web server that uses HTTP.

By default, Windows Server 2003 does not have FrontPage 2002 Server Extensions installed. If you want to use Visual Studio to publish to a Windows Server 2003 Web server that uses HTTP with FrontPage 2002 Server Extensions, you must install FrontPage 2002 Server Extensions first. You can perform the installation by using the Manage Your Server administration tool in Windows Server 2003.

IIS on Windows Server 2003 locks down all file types except for certain known content types (for example, .htm, .html, .txt, and so on). To enable deployment of ClickOnce applications using this server, you need to change the IIS settings to allow downloading files of type .application, .manifest, and any other custom file types used by your application.

If you deploy using an IIS server, run inetmgr.exe and add new File Types for the default Web page:

• For the .application and .manifest extensions, the MIME type should be "application/x-ms-application." For other file types, the MIME type should be "application/octet-stream."

• If you create a MIME type with extension "*" and the MIME type "application/octet-stream," it will allow files of unblocked file type to be downloaded. (However, blocked file types such as .aspx and .asmx cannot be downloaded.)

For specific instructions on configuring MIME types on Windows Server 2003, refer to Microsoft Knowledge Base article KB326965, "IIS 6.0 Does Not Serve Unknown MIME Types" at http://support.microsoft.com/default.aspx?scid=kb;en-us;326965.

When publishing over HTTP, the content type (also known as MIME type) for the .application file should be "application/x-ms-application." If you have .NET Framework 2.0 installed on the server, this will be set for you automatically. If this is not installed, then you need to create a MIME type association for the ClickOnce application vroot (or entire server).

If you deploy using an IIS server, run inetmgr.exe and add a new content type of "application/x-ms-application" for the .application extension.

With ClickOnce, you can perform downloads that use HTTP compression, a Web server technology that uses the GZIP algorithm to compress a data stream before sending the stream to the client. The client—in this case, ClickOnce—decompresses the stream before reading the files.

If you are using IIS, you can easily enable HTTP compression. However, when you enable HTTP compression, it is only enabled for certain file types—namely, HTML and text files. To enable compression for assemblies (.dll), XML (.xml), deployment manifests (.application), and application manifests (.manifest), you must add these file types to the list of types for IIS to compress. Until you add the file types to your deployment, only text and HTML files will be compressed.

For detailed instructions for IIS, see the article "How to Specify Additional Document Types for HTTP Compression" in the MSDN Online Knowledge Base (from the Knowledge Base Search page, search for "234497").

Concepts