Problem with SetupDiEnumDeviceInterfaces()

  • Thread starter Thread starter Jason
  • Start date Start date
J

Jason

Hello,

I'm trying to call this method from C# but it's returning false.
Marshal.GetLastWin32Error() returns 8 which means "Not enough storage is
available to process this command". Can someone elaborate what this means
please? Is this a marsahling parameter problem?

I've declared the method as
[DllImport("setupapi.dll")]
public static extern bool SetupDiEnumDeviceInterfaces(
IntPtr DeviceInfoSet, SP_DEVINFO_DATA DeviceInfoData, ref Guid
InterfaceClassGuid,
int MemberIndex, SP_DEVICE_INTERFACE_DATA DeviceInterfaceData );


I set up the return data structure by
SP_DEVICE_INTERFACE_DATA devdata = new SP_DEVICE_INTERFACE_DATA();
devdata.SetSize();

I've hardcoded the size since I can't used sizeof().

Then I call
if( !SetupDiEnumDeviceInterfaces( info, null, ref guid, instance,
devdata ) )
....

Both SP_DEVINFO_DATA and SP_DEVICE_INTERFACE_DATA have been declared as
classes so I can pass null if needed.
[StructLayout(LayoutKind.Sequential)]
public class SP_DEVICE_INTERFACE_DATA
{
internal UInt32 cbSize;
internal Guid InterfaceClassGuid;
internal UInt32 Flags;
internal IntPtr Reserved;

public void SetSize()
{
cbSize = 32;
InterfaceClassGuid = Guid.NewGuid();
}
}

I've tried the same thing with C++ and it works. I don't really want to
create a managed C++ dll to use this function so I'd greatly appreciate any
suggestions to where I'm going wrong.

Regards,

Jason Browne.
 
Jason,
I've hardcoded the size since I can't used sizeof().
Click to expand...

You can use Marshal.SizeOf().

[StructLayout(LayoutKind.Sequential)]
public class SP_DEVICE_INTERFACE_DATA
{
internal UInt32 cbSize;
internal Guid InterfaceClassGuid;
internal UInt32 Flags;
internal IntPtr Reserved;

public void SetSize()
{
cbSize = 32;
InterfaceClassGuid = Guid.NewGuid();
}
}
Click to expand...

Unless you're running on a 64-bit OS, the total size should be 28
bytes, not 32 (since a Guid32 is 16 bytes, UInt32 is 4 and IntPtr is 4
or 8 depending of the platform).



Mattias
 
Mattias Sjögren said:
Jason,


You can use Marshal.SizeOf().
Click to expand...

Cheers, I missed that. Very useful.
[StructLayout(LayoutKind.Sequential)]
public class SP_DEVICE_INTERFACE_DATA
{
internal UInt32 cbSize;
internal Guid InterfaceClassGuid;
internal UInt32 Flags;
internal IntPtr Reserved;

public void SetSize()
{
cbSize = 32;
InterfaceClassGuid = Guid.NewGuid();
}
}
Click to expand...

Unless you're running on a 64-bit OS, the total size should be 28
bytes, not 32 (since a Guid32 is 16 bytes, UInt32 is 4 and IntPtr is 4
or 8 depending of the platform).
Click to expand...

Oops, yes it should be 28 but I got desperate when I was getting that "Not
enough storage is available to process this command" error message so I
started experimenting! That wasn't supposed to be in the post :-)

As there was no comment on how the method was declared, I've been back over
the code and discovered my error. I declared DIGCF_DEVICEINTERFACE to be 10
instead of 0x10! That's solved that error.

Thanks Mattias for taking the time to look at my problem and pointing out
Marshal.SizeOf() to me.

Jason Browne.
 
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