To use the HIDClass application under 64-bit Windows, make these changes:

1. Change:

MyDeviceInterfaceData.cbSize = 28 

To:

MyDeviceInterfaceData.cbSize = 32

2. Change:
 
Marshal.WriteInt32(DetailDataBuffer, 4 + Marshal.SystemDefaultCharSize)

To:

Marshal.WriteInt32(DetailDataBuffer, 8);
 
3. Change:

SECURITY_ATTRIBUTES struct 

To:

a class

4. Change 

“ref Security” 

To:

null
 
5. For ReadFile and WriteFile, change:

ref byte lpbuffer

To:

byte[] lpbuffer

Many thanks to Yu Jye, Foo for sharing these.

The HIDClass application is available from www.Lvr.com/hidpage.htm.