>I've included the listing of the relevant code below.

> [MarshalAs(UnmanagedType.LPStruct)]
> BIRDREADING[] reading = new BIRDREADING [BIRD_MAX_DEVICE_NUM
>+ 1];

marc joanisse wrote:
> Hi Folks,
> I am writing a c# app that interacts with some scientific hardware (a
> "bird", which is just a magnetic tracker) through a C++ DLL. The
> procedure birdGetFrame(), reads data from the hardware. The second
> parameter a pointer to the struct BIRDFRAME, into which all
> the data are written when the procedure returns successfully. BIRDFRAME
> itself contains variables of other struct types as you can see below.
>
> When I call the procedure, I get an unhandled exception with the
> following error: "Can not marshal parameter #2: The type definition of
> this type has no layout information."
>
> It seems that even though I crate a new variable "pframe" of type
> BIRDFRAME the procedure cannot pass a pointer to it. I can't tell if
> the problem is how I set up pframe, or whether the BIRDFRAME struct is
> itself poorly constructed. Any help is appreciated.
>
> I've included the listing of the relevant code below.
>
> -Marc-
>
> Listing:
>
> [DllImport("bird.dll", EntryPoint = "birdGetFrame",
> CharSet=CharSet.Auto,SetLastError=true)]
> static extern bool birdGetFrame(int nGroupID,
> [MarshalAs(UnmanagedType.LPStruct)] ref BIRDFRAME pFrame);
>
> // Bird position structure
> public class BIRDPOSITION
> {
> short nX; // x-coordinate
> short nY; // y-coordinate
> short nZ; // z-coordinate
>
> }
>
> // Bird angles structure
> public class BIRDANGLES
> {
> short nAzimuth; // azimuth angle
> short nElevation; // elevation angle
> short nRoll; // roll angle
>
> }
>
> // Bird matrix structure
> public class BIRDMATRIX
> {
> short[,] n= new short [3,3]; // array of matrix
> elements
>
> }
>
> // Bird quaternion structure
> public class BIRDQUATERNION
> {
> short nQ0; // q0
> short nQ1; // q1
> short nQ2; // q2
> short nQ3; // q3
>
> }
>
> // Bird reading structure
> public class BIRDREADING
> {
> BIRDPOSITION position; // position of receiver
> BIRDANGLES angles; // orientation of
> receiver, as angles
> BIRDMATRIX matrix; // orientation of
> receiver, as matrix
> BIRDQUATERNION quaternion; // orientation of receiver, as
> quaternion
> short wButtons; // button states
>
> }
>
> // Bird frame structure
> public class BIRDFRAME
> {
> int dwTime; // time at which readings were taken, in
> msecs
> [MarshalAs(UnmanagedType.LPStruct)]
> BIRDREADING[] reading = new BIRDREADING [BIRD_MAX_DEVICE_NUM
> + 1];
> // reading from each bird
>
> }
>
> // code to read data from bird
>
> BIRDFRAME pframe = new BIRDFRAME();
>
> birdGetFrame(0, ref pframe); // **** error occurs here ****