DWORD* in C#

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GoldenK - 03 Jul 2006 10:39 GMT

Hi,

I have an unmanaged dll 'BeHwAPI.dll', on which I want to call two methods
'GetPortRtsTimerResolution' and 'SetPortRtsTimerResolution' from C#. I have
the following doc.:

BEHWAPI_API BOOL GetPortRtsTimerResolution(HANDLE hComPort,DWORD*
dwMicroSeconds);
BEHWAPI_API BOOL SetPortRtsTimerResolution(HANDLE hComPort,DWORD
dwMicroSeconds);

I have tried the following:
[DllImport("BeHwAPI.dll", EntryPoint="GetPortRtsTimerResolution")]
internal static extern bool GetPortRtsTimerResolution(IntPtr hComPort, ref
UInt32 microSeconds);
[DllImport("BeHwAPI.dll", EntryPoint="SetPortRtsTimerResolution")]
internal static extern bool SetPortRtsTimerResolution(IntPtr hComPort,
UInt32 microSeconds);

If I call
bool ok = GetPortRtsTimerResolution((int)comPort, ref rtsRes);

It return true, but the value I retrieve is always 0 - even though I have
just tried to set another value.

My question is do I use the correct datatype and reference for DWORD*?

Thanks in Advance.

Reply to this Message

Michael C - 05 Jul 2006 01:39 GMT

> My question is do I use the correct datatype and reference for DWORD*?

Yes, although I would use out instead as this allows you to pass in
uninitialized data and change from uint32 to int32 (dword is signed isn't
it?). I'm not sure if the [Out] attribute is required or not. You could also
try the [Out] attrib with ref as well.

[DllImport("BeHwAPI.dll", EntryPoint="GetPortRtsTimerResolution")]
internal static extern bool GetPortRtsTimerResolution(IntPtr hComPort,
[Out] out
int32 microSeconds);

Michael

Reply to this Message

Mattias Sjögren - 05 Jul 2006 07:20 GMT

>and change from uint32 to int32 (dword is signed isn't it?).

No it's unsigned.

>I'm not sure if the [Out] attribute is required or not.

Not if you use out.

>You could also try the [Out] attrib with ref as well.

That's effectively the same as using the out keyword.

Mattias

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Mattias Sjögren [C# MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
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GoldenK - 05 Jul 2006 07:55 GMT

Hi Mattias,

does this mean that you think I'm doing this the right way. Because then I
will talk to the hw vendor.

thanks.

Lars

> >and change from uint32 to int32 (dword is signed isn't it?).
>
[quoted text clipped - 9 lines]
>
> Mattias

Reply to this Message

Christian Fröschlin - 05 Jul 2006 10:02 GMT

> Hi Mattias,
>
> does this mean that you think I'm doing this the right way. Because then I
> will talk to the hw vendor.

What does BEHWAPI_API resolve to? It might use
a special calling convention like _cdecl.

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DWORD* in C#

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