How to change ProductCode using Microsoft.Deployment.WindowsInstaller?

Question

In a deployment scenario we had the idea to allow an administrator to change properties in a installer and the ProductCode. The administrator should then push out the newer msi using a GPO policy. Since this now would be a MajorUpgrade the old version, with the old properties, should be uninstalled and the new one, with the new properties, should be installed.
However updating the ProductCode doesn't work.

When executing
db.Execute("UPDATE Property SET Value = '{30571D61-8994-449B-9725-90760DFE0467}' WHERE Property = 'ProductCode'")
an exception is thrown.
[Microsoft.Deployment.WindowsInstaller.InstallerException] = {"Function failed during execution. Database: C:\..\MyInstaller.msi Table(s) Update failed."}

What should I do to upgrade the ProductCode?
(Is it even possible?)

Edit:
If the table is opened as ReadOnly, it will show error.
Which was the case here.

Answer 1

The SDK documentation states that ExecuteScalar can only be used for a SELECT statement that returns a single result. Instead you should use the Execute method.

using (Database database = new Database(@"C:\MSM\ISWIX.MSI", DatabaseOpenMode.Direct))
{
    database.Execute("UPDATE Property SET Value = '{00000000-0000-0000-0000-000000000000}' WHERE Property = 'ProductCode'");
}

Also realize this cannot be done as a custom action during the installation as ProductCode is immutable. Typically in a MajorUpgrade scenario you assign a new ProductCode at build/compile time.