Need a help for USB Communication in C# Using Windows API's

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C#

Dear All,

I am using C# to communicate with an external hardware unit connected to the PC.
I am still in the initial stage of USB communication,actually speaking device enumeration.

I am using "SetupDiEnumDeviceInterfaces" metod in windows API's to enumerate the devices connected.
But I always get "false" with error "259".I can't understand the error related to this code.
I will be very thankful if some one can reply me.

Code:

private class Sp_DEVICE_INTERFACE_DETAIL_DATA
{
  public int cbsize;
  public string Devicepath;
}

private class SP_DEVICE_INTERFACE_DATA
{
  public int cbSize;
  public Guid InterfaceClassGuid;
  public int FLAGS;
  public int Reserved;
};

[DllImport("hid.dll")]
private static extern void HidD_GetHidGuid(ref Guid GUID);

[DllImport("setupapi.dll", CharSet = CharSet.Auto)]
private static extern IntPtr SetupDiGetClassDevsA(ref Guid ClassGuid, UInt32 Enumerator, IntPtr hwndParent, UInt32 Flags);

IntPtr deviceinfoset;

[DllImport("setupapi.dll")]
private static extern Boolean SetupDiEnumDeviceInterfaces(IntPtr DeviceInfoSet, int DeviceInfoData, ref Guid InterfaceClassGuid, int MemberIndex, ref SP_DEVICE_INTERFACE_DATA DeviceInterfaceData);
SP_DEVICE_INTERFACE_DATA MyDeviceInterfaceData = new SP_DEVICE_INTERFACE_DATA();
int MemberIndex;
Boolean Result;

[DllImport("setupapi.dll", CharSet = CharSet.Auto)]
private static extern Boolean SetupDiGetDeviceInterfaceDetail(IntPtr DeviceInfoSet, ref SP_DEVICE_INTERFACE_DATA DeviceIntefaceData, IntPtr DeviceInterfaceDetailData, int DeviceInterfacedetailDatasize, ref int DeviceInterfacedetaildataSize, IntPtr DeviceInfoData);
int BufferSize;
Boolean Success;
int counter;

public void Initialize_Device(){
  counter = 0;

  Guid hidguid = new Guid();
  HidD_GetHidGuid(ref hidguid);

  const int DIGCF_PRESENT = (0x00000002);
  const int DIGCF_DEVICEINTERFACE = (0x000000001);
  deviceinfoset = SetupDiGetClassDevsA(ref hidguid, 0, IntPtr.Zero, DIGCF_PRESENT | DIGCF_DEVICEINTERFACE);

   listBox1.Items.Add("Device Info Set=" + deviceinfoset.ToString());
   listBox1.Items.Add("HidGuid=" + hidguid.ToString());

  

   MyDeviceInterfaceData.cbSize = 28;
   MyDeviceInterfaceData.InterfaceClassGuid = System.Guid.Empty;
   MyDeviceInterfaceData.FLAGS = 0;
   MyDeviceInterfaceData.Reserved = 0;
   MemberIndex = 0;
   Result = SetupDiEnumDeviceInterfaces(deviceinfoset, 0, ref hidguid, MemberIndex, ref MyDeviceInterfaceData);

   listBox1.Items.Add("Result=" + Result.ToString());

}

//the above method is called at the click event of a button

[edit]Code block added - OriginalGriff[/edit]