Wow, lots of bugs that needed fixing. There are still some things I'd like to improve, but they can wait. This is officially the first release of XapHandler, for stock ROMs with WP7 Root Tools, and optionally for custom ROMs as well.
1) Install XapHandler.
2) Run WP7 Root Tools.
3) Pivot to Policies, and set XapHandler as trusted (stock ROMs only).
4) Run XapHandler.
5) When prompted to set the file association, hit OK.
6) Exit XapHandler.
7) Open a XAP file from email, IE, or an app.
8) Check the data about the app given in XapHandler.
9) If the app is already installed and you want to do a clean install, exit XapHanderl and delete the app from your phone normally, then open the XAP file again.
10) Hit the Clean Install or Update button.
11) Wait for the Success message box.
12) Close XapHandler.
I don't have permission to release the actual XAP installation source code, which is from @ultrashot. Therefore, the source release just contains a pre-compiled static library (it's the same code as is used in the native XAP installer on custom ROMs, and the Bazaar app). You're able to build the full app, though.
The app has two parts: the native ARM DLL that has the COM library and does the actual installation, and the C#/Silverlight WP7 app that provides the UI and calls the COM library. You should unpack both parts to the same folder. Then, build the native part first (requires Visual Studio 2008 with the Windows Mobile 6.5 compiler). This will copy the native DLL into the managed app. Make sure the managed app includes the COM DLL, and then build it to produce a XAP file.
If you have any issues, please report the following info:
A) Your phone model.
B) Your ROM (including version and firmware)
C) The problems or exception messageboxes you encountered.
RESTORING THE REGISTRY:
For stock ROMs, if you want to put the registry back the way it was so XAP files open in the built-in XAP handler of your custom ROM:
1) Open a registry editor
2) Go to HKEY_CLASSES_ROOT (HKCR)\.xap
3) Change the default value back to what it used to be
3.1) The original value on most custom ROMs should be "xapfile" which is the same value the app uses; don't panic if it's unchanged!
3.2) The old default value *should* be backed up in a registry value simply called "0"
4) If there's a value called 0, delete it
5) Go to HKCR\<originalClassName>
5.1) For most people, that's HKCR\xapfile
6) Change the default value back to what it used to be
6.1) The original value on most custom ROMs should be empty
6.2) This step is not important; the value is cosmetic and intended for the user
6.3) The old default value *should* be backed up in a registry value simply called "0"
7) If there's a value called 0, delete it
8) If you have a registry key called BrowseInPlace (eg. HKCR\xapfile\BrowseInPlace) you can delete it
8.1) I don't *think* it'll hurt anything if left, though
9) Set the registry value EditFlags to DWORD 65536 (0x00010000)
9.1) This value is set by release versions of XapHandler
9.2) If the value is missing, create it with the data listed above
10) Go into the registry keys "shell", "open", and "command"
10.1) For example, HKCR\xapfile\shell\open\command
11) Change the default value back to what it used to be
11.1) The default value on most custom ROMs should be "XAPDeployer.exe "%1"" (remove first and last quotes)
11.3) The old default value *should* be backed up in a registry value simply called "0"
12) If there's a value called 0, delete it
13) If you had to change anything in step 3, go to HKCR
13.1) Don't do this step if you didn't have to change anything in step 3!
14) Delete HKCR\xapfile and all its contents
14.1) This step isn't needed, just cleanup
14.2) Don't do this step unless you had a different original progID than "xapfile"!
Please feel free to include this app in WP7 homebrew collections or custom ROMs, so long as the Author attribution is not removed.
Total downloads of the test versions: 330.