dll problems

[ern297]

I am trying to reuse in C# one function written in Visual C++ 6.0 that is in a DLL. Function has the following head:

type_enum name_function(
unsigned long *var1,
unsigned long var2,
wchar_t *var3);

I am trying to use the following thing, but it does not work.

[DllImport("library.dll", EntryPoint="name_function&quot]
static extern type_enum name_function(
ref ulong var1,
ulong var2,
ref char var3);

Could somebody help me?

 

[alexboly]

I have read in MSDN that for passing structures as attributes to an unmanaged function you need to use a special mechanism, by using the StructLayout attribute. I am only guessing now, but isn't it necessary to use this also when the function returns a structure? Have you tried to do a platform invoke with a function that returns a simple type (e.g. int)?
If that's not it, could you specify the error message(s) you receive when you run your program?

 

[ern297]

I've rewrite my DLL to:

[DllImport("myDll.dll", EntryPoint="theFunction&quot]
public static extern type_enum myFunction(
[MarshalAs(UnmanagedType.U8)]ref ulong var1,
[MarshalAs(UnmanagedType.U8)]ulong var2,
[MarshalAs(UnmanagedType.LPWStr)]ref char var3);

I don't pass any structure (I think. It's only an enum type), but I have the next error:

No se pueden calcular referencias de parameter #3: combinación de tipos administrado y no administrado no válida (los caracteres deben estar emparejados con U1 o U2).


I traduce it as:

References of parameter # 3 cannot be calculated: combination of types administered and not administered is not worth (the characters must be matched with U1 or U2).


I don't understand where I must use the StructLayout that you say. Could you help me?

 

[ern297]

Thanks for everything, but finally I have obtained it!
This is the 'winner code':

[DllImport("myLib.dll", EntryPoint="theFunction&quot]
public static extern TYPE_ENUM myFunction(
[MarshalAs(UnmanagedType.U4)]ref uint var1,
[MarshalAs(UnmanagedType.U4)]uint var2,
[MarshalAs(UnmanagedType.U2)]ref char var3);

 

[alexboly]

Yes, after seeing the error message it gets clear...
I'm glad that you did it...