P/Invoke with strings in Compact Framework 2.0 SP2

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If I call the native DLL like this:

*** string dfhgfdgh = "jhdgjhdjghjdtgyhn";

 

[DllImport("StringTestNativeDLL", CallingConvention = CallingConvention.Winapi)]

public static extern byte GetVehicleIdentification(ref string vehicleIdentification);

 

private void button1_Click(object sender, EventArgs e)

{

* GetVehicleIdentification(ref dfhgfdgh);

* textBox1.Text = dfhgfdgh;

}

and the native DLL looks like this:

char m_VehicleIdentification[200];

 

extern "C" __declspec(dllexport) BYTE __stdcall GetVehicleIdentification(wchar_t** vehicleIdentification)

{

* strcpy(m_VehicleIdentification, "1234567890");

* strcpy (*vehicleIdentification, m_VehicleIdentification);

* return 0;

}

The text in my textbox is a sequence of squares equal to half the number of characters in the string above i.o.w. 5 squares (unrecognized characters)

It seems like it’s trying to interpret the ascii-string as a unicode string (2 bytes per character). If I try to

public static extern byte GetVehicleIdentification([MarshalAs(UnmanagedType.LPStr)]ref string vehicleIdentification);

I get a “Not supported”-exception. I get the same result for LPTStr LPWStr BStr BTStr and all other string types which I have tried.

Is it not possible in the Compact Framework to call a native function which has a char** in-parameter and get a valid string back in any other way than to work with wchar_t** in the native function? I don’t want to use unsafe C#-code. (If cut the ref and use char* instead in the native function I get the same result, .)

 

 

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