Ways to access a 32bit DLL from a 64bit exe

Question

I have a project that must be compiled and run in 64 bit mode. Unfortunately, I am required to call upon a DLL that is only available in 32 bit mode, so there\'s no way I ca

Answer 1

None. Point. 32 bit dll in 64 bit process = no go.

What I do is run a 32 bit wrapper process and communicate with it using WCF - much like you do. I can force the OS to run 32 bit.

I have a core library (Tradex.Connectivity.Core), with the platform independant .NET code. I have two wrappers (Wrapper32.exe, Wapper64.exe) that start and load the independent code and then load the class (managed C++). Works like a charm.

THat pretty much is the only way for me - you can not crss load 32 and 64 bit elements.

Answer 2

I know this answer might be a little bit late, but some time ago I faced the exact same problem (loading a 32bit dll into an AnyCPU assembly on a 64bit machine).

As a solution, I wrote the LegacyWrapper. It basically consists of a 32bit wrapper exe loading the desired dll, communicating with your application via Named Pipes.

A call would look like this:

// Define delegate matching api function
private delegate int GetSystemMetrics(int index);

// Create new WrapperClient
// Remember to ensure a call to the Dispose()-Method!
using (var client = new WrapperClient())
{
    // Make calls providing library name, function name, and parameters
    int x = (int)client.Invoke<GetSystemMetrics>("User32.dll", "GetSystemMetrics", new object[] { 0 });
    int y = (int)client.Invoke<GetSystemMetrics>("User32.dll", "GetSystemMetrics", new object[] { 1 });
}

For some details, you can refer to this blog post.

Edit: Since Version 2.1, LegacyWrapper also supports loading 64bit DLLs from a 32bit process.

Answer 3

As you correctly note, there is no way to mix bitness in the same process. You need a separate process for your 32-bit part.

I think hosting a WCF Service is the right way to go. Your link only talks about wcfsvchost. I am pretty sure you can create your own Windows Service, and host the WCF service in that on 32 bit.

See this link: How to host a WCF service in a managed application. You can host your service in any managed application, including a Windows Service, and run it under the bitness you like.

This is the amount of code required to self-host a WCF service in your application, assuming you have just created a new service called MyService, and the appropiate configuration has been added to app.config:

class Program
{
    static void Main(string[] args)
    {
        using(ServiceHost host = new ServiceHost(typeof(MyService), new Uri[0]))
        {
            host.Open();
            Console.ReadKey();    
        }
    }
}

The above program will run just as well, also if you compile it explicitly as 32 or 64 bit.