Strangelights

I recently had to create an msi installer that ran ngen on each of the assemblies that I installed. I had a number of difficulties doing this, so I thought I share my findings here an hopefully save others a bit of time.

I won’t have been able to do this at all with out orca, an MSI decompiler supplied with the installer section of the platform SDK. Also looking at the definitions of the MSI tables helped a lot.

The CustomActions is a bit of a strange beastie, it has just 4 column, these are Action (the primary key), Type, Source and Target, but the mean of the columns Sources and Target can vary radically depending on the integer value in Type. Wix does not allow you to directly add values to Type column; it provides a number of different properties, with each property representing a different type of thing that could go in the CustomActions table. From the action that you describe using the properties it then works out what type of action you want. This sounds more complex than it really is, for example if you have a custom action tag <CustomAction Id=”” VBcriptCall=”MsgBox ‘dump thing to do’”> a custom action of Type 6 gets generated because Type 6 is a VBScript call.

I looked at the windows installer documentation for the CustomActions table. From a quick review of the list of custom action types I saw that I either needed an action of 34 or 50. I plumped for type 50 for no other reason than I figured out the wix syntax to generate this first. For reasons I’ll explain later I may have been better going for a type 34, but for now I’m happy with what I’ve got.

Actions of type 50 require an entry in the property table that points to the executable location a foreign key to the property table is placed in the Source column and the Target column is the command line parameters for the executable.

Creating an entry in the property table is easy, the syntax is given below. But this is why I suggest a Type 34 might have been more appropriate. Entries in the property table provide no way of giving indirection to well know directories, so I was stuck with hard coding the path. I tried using the %windir% shell environment variable syntax, [%windir] msi environment variable syntax and [WindowsDirectory] to reference the msi property. None worked; it has to be just a plain old string. This is okay for me as my msi only be deployed on environments that we control, so we can be sure ngen will always be in the same place.

<Property Id="NGenLocationProperty" Value="c:\windows\Microsoft.NET\Framework\v1.1.4322\ngen.exe" />

Now to add the CustomAction all we need to do is add a custom action tag, the syntax for this is shown below. The ExeCommand property contains the command line parameters, the most important thing to note about these is I can refernce the full file path of a file in my wix script using the syntax [#FileId] where FileId is the Id property of a file tag.

<CustomAction Id="Test.exeFileNGen" ExeCommand='"[#DataPharm.PharmaNet.Logging.dllFile]"' Property="NGenLocationProperty" />

You then need to ensure you CustomAction is run by giving it an entry in the InstallExecuteSequence table. This is dead easy and the syntax is shown below. The only thing you have to whatch is the After property on the Custom tag, I found this had to be InstallFinalize as the files haven’t been written to disk until after this.

<InstallExecuteSequence>

<Custom Action="Test.exeFileNGen" After="InstallFinalize" />

</InstallExecuteSequence>

That about it, the full script is available for down load here. It should compile, but will require a .Net assembly called test.exe in the same directory to link. The script also has an example of a short cut but I don’t feel that really needs any explanation.