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Hi guys,
I want to control some USB-measurement device (spectrometer) and they gave me this dll: specu1a.dll
The manufacturer gave me some VB-Code which is working and the Interop-Decleration looks like this:
Public Declare Ansi Function USB_OpenDevice Lib "specu1a.dll" Alias "USB_OpenDevice" ( _
                    ByVal ProductID As UShort _
                    ) As Integer

This Code works and the function return a valid Integer representing the DeviceHandle
I am not new to DllImport stuff so I tried the function to open the device like this:
public static extern int USB_OpenDevice(ushort ProductID);

And? result=-1
even more sofisticated attempts like this:
[DllImport("specu1a.dll", CallingConvention=CallingConvention.StdCall, CharSet=CharSet.Ansi)]
public static extern unsafe int USB_OpenDevice([MarshalAs(UnmanagedType.U2)]ushort ProductID);

came out with the same...
There is no error Message from VS2012, I use x86 build settings and this "Marshal.Prelink(Methodinfo USB_OpenDevice)" also gives no error so the dll should be loading correctly.
Updated 1-Mar-13 7:31am
Sergey Alexandrovich Kryukov 1-Mar-13 13:37pm    
At first glance, looks correct. Are you sure that CPU instruction-set architectures match? Is the target platforms of this VB library x86? Is the target platform of your application assembly (important! The one where your entry-point is, not the one importing the library!) also x86?
By the way, you don't need both Marshal as; you only need to check that the type sizes match (as well as signed/unsigned; sorry, I'm not using VB, please check up; I think they are correct).
Niles Davis 2-Mar-13 5:13am    
platform and sizes are matching as well as platform, but that did not help.
Sergey Alexandrovich Kryukov 1-Mar-13 13:42pm    
And I really sorry for your troubles. Those manufacturers of such equipments are mostly so illiterate in computing! And the mere fact they offer VB (VB6?) these days, looks very suspicious: these days, many manufacturers improved their work a bit, and often offer .NET interface libraries.
I deal with those hardware interfaces many years, many of those manufacturers make most idiotic "solution" in their "software". Unfortunately...
Richard MacCutchan 1-Mar-13 13:48pm    
Wouldn't it be more sensible to ask this question of the people who provided the library?
Sergey Alexandrovich Kryukov 1-Mar-13 21:55pm    
You are right, but... look at what kind is the library is. I tried to ask manufacturer's representative many times, not that they are not responsive enough, but... very hard to reach a person who understand the matter at least a bit. But of course OP should try...

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