COM object only works in VB.NET not C#

Question

I have a COM object that works fine in VB.NET, but not in C#. Both projects are .NET 4 console applications.

The COM object loads in C#, but the methods don't return any values. Why would it work in VB.NET and not C#?

Thanks!

Sub Main()
    Dim server As New NoahVersionLib.Version

    Dim val As Int32

    server.GetNoahServerVersionMS(val)



End Sub


    static void Main(string[] args)
    {
        var server = new NoahVersionLib.Version();

        int val= 0;

        server.GetNoahServerVersionMS(ref val);
    }

val is 0 in the C# build, but has a value in the VB.NET build.

UPDATE:
I needed to put [STAThread] on my Main() in C#. It works now.

please show a minimal but working (i.e. compiling) code sample illustrating the problem in both environmnents. tinyurl.com/so-hints — jeroenh
– jeroenh, Commented May 10, 2011 at 13:50
There's no special reason why it would only work in VB.NET and not in C#. They compile down to the same code. The only way that we can answer this question is if you provide us with a minimal sample that reproduces the behavior. Chances are, there's an error in how you're converting the VB.NET code into C#. — Cody Gray
– Cody Gray ♦, Commented May 10, 2011 at 13:57
Have a look at both exe files in ildasm. Do you see a difference in the generated IL code? If yes, what is it? — Heinzi
– Heinzi, Commented May 10, 2011 at 14:14
also, it makes on difference in the C# build if var is used instead of NoadVersionLib.Version. — Derek
– Derek, Commented May 10, 2011 at 14:15

Derek · Accepted Answer · 2011-05-11 13:34:15Z

1

I needed to put [STAThread] on my Main() in C#. It works now.

answered May 11, 2011 at 13:34

Derek

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Comments

Jaymz · Accepted Answer · 2011-05-10 15:06:17Z

0

Have you tried the following in C#?

static void Main(string[] args)    
{        
    NoahVersionLib.Version server = new NoahVersionLib.Version();        
    Int32 val= 0;        
    server.GetNoahServerVersionMS(ref val);    
}

The only differences between your 2 versions are that you are using var instead of declaring the actual type, allowing the compiler to potentially infer an incorrect type (unlikely, but surely possible); and use of int instead of Int32. As far as I know, int == Int32, but possibly in some weird corner case of COM, it may not..?

answered May 10, 2011 at 15:06

Jaymz

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