Writing to the Windows Installer log file from a Custom Action

This blog entry provides an example of writing to the windows installer log file from a custom action using VBScript.  It follows on from the previous blog post which provided a tutorial on using SQL inside an MSI database custom action using VBScript.

It forms part 15 of an 17-part series that explores how to use VBScript to manipulate MSI relational databases using the Windows Installer API.  Throughout this series of tutorials, we identify the common issues that we encounter and the best practises that we use to overcome them.

Logging is extremely useful when debugging MSIs. Most people that write Custom Actions don’t write logs, but if you’re writing quite extensive logic you may wish to consider it. Simply paste the following logic into your CA:

'Subroutine to write to log file 
Const msiMessageTypeInfo = &H04000000
Sub writeToLog(ByVal msg)
	Set record = Installer.CreateRecord(1)
	record.stringdata(0) = "AlkaneLog: [1]"
	'This value gets subbed in to the [1] placeholder above
	record.stringdata(1) = msg
	record.formattext
	message msiMessageTypeInfo, record
	Set record = Nothing
End Sub

and write to the log like this:

writeToLog("This is a log message")

Thanks for reading about writing to the Windows Installer log file from a Custom Action using VBScript.  Next you can find out how to edit MSI files in the windows installer cache using VBScript.

Inserting a registry value in an MSI database (Modify method)

This blog entry provides an example of inserting a registry value in an MSI database using the Modify method and VBScript.  It follows on from the previous blog post which provided a tutorial on deleting a registry value from an MSI database using the Modify method and VBScript.

It forms part 9 of an 17-part series that explores how to use VBScript to manipulate MSI relational databases using the Windows Installer API.  Throughout this series of tutorials, we identify the common issues that we encounter and the best practises that we use to overcome them.

In this example, we run a SQL statement to include the columns of data which we want to insert – this also helps us to identify if the row of data already exists before we try to insert it!

Note that we MUST include all of the non-nullable columns as a minimum in the SQL statement. When a column is not nullable, it means we MUST specify a value when we insert the record. Otherwise the insertion will fail. To find the non-nullable columns, consult the Windows Installer help file (MSI.chm) or MSDN. For example:

Inserting a registry value in an MSI database (Modify method) 1

The four non-nullable columns which we MUST include when inserting into the Registry table are:

Registry
Root
Key
Component_

Dim sql : sql = "SELECT `Registry`,`Root`,`Key`,`Component_` FROM `Registry` WHERE `Registry` = 'MyNewSampleReg'"

If we were lazy, we could just return all rows using the following:

Dim sql : sql = "SELECT * FROM `Registry` WHERE `Registry` = 'MyNewSampleReg'"

This time when we execute the query, we’re not going to loop through any records using the While…Wend loop. All we want to do is see if the record already exists:

If regRecord Is Nothing Then

and if it doesn’t, we’ll start to create a new record and populate the values….

'There are no records returned, so we create a new record
    Set regRecord = oInstaller.CreateRecord(4)

    'in this example, we've created a record ensuring that all the non-nullable field are populated
    regRecord.StringData(1) = "MyNewSampleReg"
    regRecord.IntegerData(2) = 2
    regRecord.StringData(3) = "SOFTWARE\alkaneTest"
    regRecord.StringData(4) = "alkaneComponent"

Note how we’ve used StringData for columns which can accept strings as their data types, and IntegerData for columns which accept numeric values only.
Again, to find columns with an ‘Integer’ data type you should consult the Windows Installer help file (MSI.chm) or MSDN.

Once we’ve created our new record, we insert it:

regView.Modify msiViewModifyInsert,regRecord

And here is the finished script:

'create 2 constants - one for when we want to just query the MSI (read) and one for when we want to make changes (write)

Const msiOpenDatabaseModeReadOnly = 0
Const msiOpenDatabaseModeTransact = 1

Const msiViewModifyInsert = 1
Const msiViewModifyUpdate = 2
Const msiViewModifyDelete = 6
Const msiViewModifyReplace = 4

'create WindowsInstaller.Installer object
Dim oInstaller : Set oInstaller = CreateObject("WindowsInstaller.Installer")

'open the MSI (the first argument supplied to the vbscript)
Dim oDatabase : Set oDatabase = oInstaller.OpenDatabase(WScript.Arguments(0),msiOpenDatabaseModeTransact) 

Dim sql : sql = "SELECT `Registry`,`Root`,`Key`,`Component_` FROM `Registry` WHERE `Registry` = 'MyNewSampleReg'"
'create a view of the registry we want to see
Dim regView : Set regView = oDatabase.OpenView(sql)

'execute the query
regView.Execute 
Set regRecord = regView.Fetch

If regRecord Is Nothing Then
	'There are no records returned, so we create a new record
	Set regRecord = oInstaller.CreateRecord(4)

	'in this example, we've created a record ensuring that all the non-nullable field are populated
	regRecord.StringData(1) = "MyNewSampleReg"
	regRecord.IntegerData(2) = 2
	regRecord.StringData(3) = "SOFTWARE\alkaneTest"
	regRecord.StringData(4) = "alkaneComponent"

	regView.Modify msiViewModifyInsert,regRecord

End If

oDatabase.Commit

regView.Close
Set regView = Nothing
Set regRecord = Nothing
Set oDatabase = Nothing
Set oInstaller = Nothing

Thanks for reading about inserting a registry value in an MSI database using the Modify method.  Next you can find out how to handle tables that don’t exist in an MSI database using VBScript.