I have a union of structs that is returned from an unmanged C++ API.
Everything works fine until I add a specific type of struct
[EvEndBitInfo] as a member of the union. I know you can't mix value and
reference types in the same union, but I don't see the conflict because
I believe all members of the suspect struct are value types. Here's
what I have:

//TypeLoadException
Could not load type ...EventInfo from assembly MyAssembly,
Version=1.0.1847.20731, Culture=neutral, PublicKeyToken=null because it
contains an object field at offset 0 that is incorrectly aligned or
overlapped by a non-object field.

// Union Definition
[StructLayout(LayoutKind.Explicit)]
public struct EventInfo
{
[FieldOffset(0)] public EvErrorInfo ErrorReport;
[FieldOffset(0)] public EvPstnErrorInfo PSTNErrorReport;
[FieldOffset(0)] public EvEndBitInfo BITReport; // here's the culprit
// additional fields...
}

// EvErrorInfo struct
[StructLayout(LayoutKind.Sequential)]
public struct EvErrorInfo
{
public int ErrorCode;
public int DeviceID;
public int CID;
public int Origin;
public int LineInFile;
[MarshalAs(UnmanagedType.ByValArray, SizeConst=8)]
public char[] FileName;
public byte Length;
[MarshalAs(UnmanagedType.ByValArray, SizeConst=255)]
public char[] ErrorString;
}

// EvPstnErrorInfo struct
[StructLayout(LayoutKind.Sequential)]
public struct EvPstnErrorInfo
{
public int ErrorCode;
public int DeviceID;
public int TrunkID;
public int BChannel;
public int ConnID;
public int Origin;
public int LineInFile;
[MarshalAs(UnmanagedType.ByValArray, SizeConst=8)]
public char[] FileName;
public byte Length;
[MarshalAs(UnmanagedType.ByValArray, SizeConst=255)]
public char[] ErrorString;
public int CallHandle;
}

// EvEndBitInfo struct ::This is the culprit::
[StructLayout(LayoutKind.Sequential)]
public struct EvEndBitInfo
{
[MarshalAs(UnmanagedType.ByValArray, SizeConst=2)]
public int[] DSPBitReturnCode;
public int FLASHBitReturnCode;
public int SDRAMBitReturnCode;
public int DPRBitReturnCode;
public int PhyTestBitReturnCode;
public int FramersBitReturnCode;
public int PCMSwitchBitReturnCode;
public int ResetSourceReportBitReturnCode;
public int NumOfAnalogChannels;
public int BoardTempBitReturnCode;
[MarshalAs(UnmanagedType.ByValArray, SizeConst=24)]
public int[] FXSCRAMCheckSumBitReturnCode;
[MarshalAs(UnmanagedType.ByValArray, SizeConst=24)]
public int[] VoltageCurrentBitReturnCode;
[MarshalAs(UnmanagedType.ByValArray, SizeConst=24)]
public int[] FXSDuslicVersionReturnCode;
[MarshalAs(UnmanagedType.ByValArray, SizeConst=24)]
public int[] FXOAnicVersionReturnCode;
[MarshalAs(UnmanagedType.ByValArray, SizeConst=24)]
public int[] FXSCodecValidationBitReturnCode;
}

The only thing that distinguishes these structs is the use of int[] in
the EvEndBitInfo struct in question. Am I mistaken that int[] is a
value type?

Thanks for any insight.