marshaling:SizeOf(object structure) error

[swts]

hi,

the following marshaling code gives me an errror of "type packet cannot be marshaled as an unmanaged structure; no meaningful size or offset can be managed".

public static byte[] StructureToBytesArray(object obj)
{
int len = Marshal.SizeOf(obj);
byte[] arr = new byte[len];
IntPtr ptr = Marshal.AllocHGlobal(len);
Marshal.StructureToPtr(obj, ptr, true);
Marshal.Copy(ptr, arr, 0, len);
Marshal.FreeHGlobal(ptr);
return arr;
}
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this is the structure i am trying to marshal an send thru the socket:

public struct packet
{
public string data;
public string D;
public string SD;
public string PD1;
public string SPD1;
public int[] SBD1;
public int[,] SBD2;

}

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byte[] str = StructureToBytesArray(pkt[j]);

i am getting an error for the Marshal.SizeOf(object structure).kindly help...


thanks in advance