How to invoke method from .NET DLL in InstallScript

Question

I need to call function from .NET DLL in InstallScript. How can I do it?

Let's start from simple Hello World. Suppose, I created simple class library TestLibrary.dll

using System;
using System.Windows.Forms;

namespace TestLibrary
{
    public static class TestClass
    {
        public static void TestFunction()
        {
            MessageBox.Show("Hello!");
        }
    }
 }

I don't want to install this DLL on a target box, I only want to run TestFunction() during installation process, so I just added TestLibrary.dll in SupportFiles view (I use InstallShield 2013 Professional, Basic MSI Project Type). Then in InstallScript I'm writing prototype for it, loading TestLibrary.dll and trying to call TestFunction from it. Something like this:

export prototype TestDllFunction(HWND); //call in Custom Action
prototype TestLibrary.TestFunction(); 
.......

function TestDllFunction(hMSI)
    NUMBER Result;
begin
    Result = UseDLL(SUPPORTDIR ^ "TestLibrary.dll");
    TestLibrary.TestFunction();
    Result = UnUseDLL("TestLibrary.dll");
end;

I've 2 problems here: UseDLL returns 0 (0 means that DLL was successfully loaded) only if I invoke UseDLL with hardcoded absolute path to TestLibrary.dll. And the second problem - suppose, I successfully loaded DLL. How can I invoke my TestFunction and see a "Hello" messagebox then?

Christopher Painter Christopher Painter · Accepted Answer · 2014-01-31T19:23:51

UseDLL only works for unmanaged code. For .NET use DotNetCoCreateObject. But to be honest, for MSI projects I'd skip InstallScript completely and use C# directly. Windows Installer XML (WiX) has a feature called Deployment Tools Foundation (DTF) which makes it possible to build a Windows Installer compatible managed custom action. The output DLL looks like a traditional Win32 DLL to Windows Installer and is compatible with InstallShield.

How to invoke method from .NET DLL in InstallScript

2 Answers