[wix-users] MsiEvaluateCondition

[Douglas, Keith (STATCAN/STATCAN)]

I was looking at both the native MsiEvaluateCondition and its DTF counterpart for use in an Condition syntax validation tool for my WiX front end. I see that the first seems to require an open package, hence a legitimate package. By contrast the DTF version requires a Session to work in. I don't care about making sure Properties etc. are recognized or environment variables resolve, just that the syntax is correct. Is there another way to validate Condition syntax without using a package or Session (which I take it would require an installation context, which I don't want)? Not really a big deal if not, but it would be nice to understand the dependencies of the tools I build. (I do know the package does not have to be installed.)

In case it matters, the code idea I had to use the native method is - calling CheckMsiCondition for the purpose mentioned above:

    public static class NativeMethods
    {
        [DllImport("msi.dll", CharSet = CharSet.Unicode)] static extern uint MsiEvaluateCondition(int hInstall, string szCondition);
        [DllImport("msi.dll", CharSet = CharSet.Unicode)] static extern uint MsiOpenPackageEx(string szPackagePath, uint dwOptions, out int hProduct);
        [DllImport("msi.dll", CharSet = CharSet.Unicode)] static extern uint MsiCloseHandle(int hAny);

        public static bool CheckMsiCondition (string whatToCheck)
        {
            int handle;
            uint result = MsiOpenPackageEx("[path to some existing MSI deleted]", (uint)0, out handle); // Use demo MSI for now.
            result = MsiEvaluateCondition(handle, whatToCheck);
            MsiCloseHandle(handle);
            return (result == 0 || result == 1);
        }
    }

Finally, I note that calling MsiOpenPackageEx seems to provoke the standard msiexec UI for installing a product anyway. Would this rule out using the call in a service even if the appearance is temporary/not used?


Keith Douglas
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