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c#.netstructuremarshalling

Marshall array of structures


I've spent a lot of time to look for the solution but still don't find it out.

I have 2 classes:

[StructLayout(LayoutKind.Sequential)]
public class Result
{
    public int Number;
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 4)]
    public string Name;
    public int Size;
}

[StructLayout(LayoutKind.Sequential)]
public class CoverObject
{
    public int NumOfResults;
    [MarshalAs(UnmanagedType.ByValArray, ArraySubType = UnmanagedType.Struct, SizeConst = 4)]
    public Result[] Results;
}

My expectation that the command Marshal.SizeOf(typeof(CoverObject)) will return 52, but not, it's just 20. Thus, all of marshall and unmarshall that I use later are not working.

Seeming it only counts the first member (Number) in Result class. Did I do anything wrong?


Solution

  • Change your classes to structs

    [StructLayout(LayoutKind.Sequential)]
    public struct Result
    {
        public int Number;
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 4)]
        public string Name;
        public int Size;
    }
    
    [StructLayout(LayoutKind.Sequential)]
    public struct CoverObject
    {
        public int NumOfResults;
        [MarshalAs(UnmanagedType.ByValArray, ArraySubType = UnmanagedType.Struct, SizeConst = 4)]
        public Result[] Results;
    }
    

    some where else:

    Marshal.SizeOf(typeof(CoverObject)) // it will return 52