Invalid Handle Exception from GetRawInputData

I am using the User32 SendMessage function to send raw keyboard input to my API.

The function that intercepts the SendMessage call is the WndProc function. This function runs the Win32 GetRawInputData function to get the data buffer from the IntPtr handle from the lParam from the message recieved by the SendMessage function.

When I run the GetRawInputData functionm I get the following error:

• >>> 6:System.ComponentModel.Win32Exception (0x80004005): The handle is invalid

How can I fix this?

Hook

//^ DLL Imports, SetWindowsHookEx, etc^

public int HookProc(int Code, int wParam, ref CWPRETSTRUCT lParam) {
    if (Code >= 0) {
        // Block
        Rawkeyboard lParamKeyboard = new Rawkeyboard();
        int result = SendMessage(Handle, 0x00FF, wParam, ref lParamKeyboard ); // Send to API
        if (result == 1) {
            return 1;
        }
    }
    // Allow
    return CallNextHookEx(Handle, Code, wParam, ref lParam);
}

[StructLayout(LayoutKind.Sequential)]
public struct Rawkeyboard {
    public ushort Makecode;                 // Scan code from the key depression
    public ushort Flags;                    // One or more of RI_KEY_MAKE, RI_KEY_BREAK, RI_KEY_E0, RI_KEY_E1
    private readonly ushort Reserved;       // Always 0    
    public ushort VKey;                     // Virtual Key Code
    public uint Message;                    // Corresponding Windows message for exmaple (WM_KEYDOWN, WM_SYASKEYDOWN etc)
    public uint ExtraInformation;           // The device-specific addition information for the event (seems to always be zero for keyboards)

    public override string ToString() {
        return string.Format("Rawkeyboard\n Makecode: {0}\n Makecode(hex) : {0:X}\n Flags: {1}\n Reserved: {2}\n VKeyName: {3}\n Message: {4}\n ExtraInformation {5}\n",
                                            Makecode, Flags, Reserved, VKey, Message, ExtraInformation);
    }
}

[StructLayout(LayoutKind.Sequential)]
public struct CWPRETSTRUCT {
    IntPtr lResult;
    IntPtr lParam;
    IntPtr wParam;
    uint message;
    IntPtr hWnd;
}

API

protected override void WndProc(ref Message message){
        switch (message.Msg){
            // Message Received!
            case 0x00FF:{
                bool result = false;
                hdevice = message.LParam;
                if (_deviceList.Count == 0) return false;
                var dwSize = 0;

                Win32.GetRawInputData(hdevice, DataCommand.RID_INPUT, IntPtr.Zero, ref dwSize, Marshal.SizeOf(typeof(Rawinputheader)));
                if (dwSize != Win32.GetRawInputData(hdevice, DataCommand.RID_INPUT, out _rawBuffer, ref dwSize, Marshal.SizeOf(typeof (Rawinputheader)))){
                    if (result == -1) { var code = Marshal.GetLastWin32Error(); var error = new Win32Exception(code); Debug.WriteLine(code + ":" + error.ToString()); }
                    Debug.WriteLine("Error getting the rawinput buffer");
                    result = false;
                }
                else{
                    // Do checks here
                    result = true;
                }
                message.Result = (IntPtr)Convert.ToInt32(result);
            }
            break;
        }
        base.WndProc(ref message);
    }


[StructLayout(LayoutKind.Sequential)]
public struct Rawinputheader
{
    public uint dwType;                     // Type of raw input (RIM_TYPEHID 2, RIM_TYPEKEYBOARD 1, RIM_TYPEMOUSE 0)
    public uint dwSize;                     // Size in bytes of the entire input packet of data. This includes RAWINPUT plus possible extra input reports in the RAWHID variable length array. 
    public IntPtr hDevice;                  // A handle to the device generating the raw input data. 
    public IntPtr wParam;                   // RIM_INPUT 0 if input occurred while application was in the foreground else RIM_INPUTSINK 1 if it was not.

    public override string ToString()
    {
        return string.Format("RawInputHeader\n dwType : {0}\n dwSize : {1}\n hDevice : {2}\n wParam : {3}", dwType, dwSize, hDevice, wParam);
    }
}