dll-import in c# with (const char far *...)

Hi All,

I'm rather new to C# and extremely new to Interop.
My problem: I have a C DLL that I need to call and I'm trying to do it in
C#. I can call the function but for some reason my C DLL doesn't seem to be
getting what I'm trying to pass it.

C function: BYTE __declspec(dllexport) StationOnline(const char far * );

my C# call is: [DllImport("xxxxxxx.dll", EntryPoint = "StationOnline")]
public static extern byte StationOnline(string
sStaName);

Anyways, my question is if I am declaring everything correctly. Even when I
know my StationOnline function should be 1 I'm getting 0.

Thanks in advance,
Greg

Greg1970 schrieb:

Hi All,

I'm rather new to C# and extremely new to Interop.
My problem: I have a C DLL that I need to call and I'm trying to do it in
C#. I can call the function but for some reason my C DLL doesn't seem to be
getting what I'm trying to pass it.

C function: BYTE __declspec(dllexport) StationOnline(const char far * );

my C# call is: [DllImport("xxxxxxx.dll", EntryPoint = "StationOnline")]
public static extern byte StationOnline(string
sStaName);

Anyways, my question is if I am declaring everything correctly. Even when I
know my StationOnline function should be 1 I'm getting 0.

Thanks in advance,
Greg

data types

unmanaged data types | managed data types(C#)
----------------------------------------------------------------
BYTE | System.Byte

**const char *** | System.String or System.StringBuilder

[DllImport("xxxxxxx.dll", EntryPoint = "StationOnline")]
public static extern System.Byte StationOnline(System.String
sStaName)

look at http://msdn2.microsoft.com/de-de/ac7ay120.aspx

or

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpconplatforminvokedatatypes.asp

LordJaxom

Well isn't System.String mapped to string and System.Byte mapped to byte in C#? AFAIK there are no language-internal datatypes that don't map to a Framework Type.

According to http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpcondefaultmarshalingforstrings.asp a c-string must be marshaled when converted to a framework string:

[DllImport("xxxxxxx.dll", EntryPoint = "StationOnline")]
public static extern byte StationOnline([MarshalAs(UnmanagedType.LPStr)] string
sStaName);