Not able to properly map c struct to c# struct

Question

I'm trying to map a bytearray in c#, which is of 56 bytes and the struct i got for it is like this in C

struct cequivalentstruct{
    uint32_t Descriptor;

    uint32_t Value;

    uint32_t Minimum;

    uint32_t Maximum;

    uint32_t Default;

    uint16_t Next;

    uint16_t Previous;

    char Units[4];

    uint16_t Multiplier;

    uint16_t Divisor;

    uint16_t Base;

    uint16_t Offset;

    char Link[3];

    char pad;

    char Name[16];
}

and i have coverted that to

         [StructLayout(LayoutKind.Sequential, Pack = 1, CharSet = CharSet.Ansi)]
        public struct ParameterResponse
        {
            [MarshalAs(UnmanagedType.U4, SizeConst = 4)]
            public uint Descriptor;
            [MarshalAs(UnmanagedType.I4, SizeConst = 4)]
            public uint Value;
            [MarshalAs(UnmanagedType.U4, SizeConst = 4)]
            public uint Minimum;
            [MarshalAs(UnmanagedType.U4, SizeConst = 4)]
            public uint Maximum;
            [MarshalAs(UnmanagedType.U4, SizeConst = 4)]
            public uint Default;
            [MarshalAs(UnmanagedType.U4, SizeConst = 2)]
            public uint Next;
            [MarshalAs(UnmanagedType.U4, SizeConst = 2)]
            public uint Previous;
            [MarshalAs(UnmanagedType.ByValArray, SizeConst = 4)]
            public char[] Units;
            [MarshalAs(UnmanagedType.U4, SizeConst = 2)]
            public uint Multiplier;
            [MarshalAs(UnmanagedType.U4, SizeConst = 2)]
            public uint Divisor;
            [MarshalAs(UnmanagedType.U4, SizeConst = 2)]
            public uint Base;
            [MarshalAs(UnmanagedType.U4, SizeConst = 2)]
            public uint Offset;
            [MarshalAs(UnmanagedType.ByValArray, SizeConst = 3)]
            public char[] Link;
            [MarshalAs(UnmanagedType.U1, SizeConst = 1)]
            public char pad;
            [MarshalAs(UnmanagedType.ByValArray)]
            public byte[] Name;
    
            public ParameterResponse(uint descriptior, uint value, uint maximum, uint minimum, uint defaultvalue, uint next, uint previous,
                char[] units, uint multiplier, uint divisor, uint baseValue, uint offset, char[] link, char padValue, byte[] name)
            {
                Descriptor = descriptior;
                Value = value;
                Maximum= maximum;
                Minimum= minimum;
                Default = defaultvalue;
                Next= next; Previous= previous;
                Units = units;
                Multiplier = multiplier;
                Divisor = divisor;
                Base = baseValue; Offset = offset;
                Link = link;
                pad = padValue;
                Name = name;
    }
    }

}

I'm not sure if I'm missing something in this, because when I try to convert my byteArray to this struct, but the struct is not exactly taking the appropriate sizeconst defined, any inputs would be helpful.

Answer 1

Try this.

uint16_t should map to ushort, char should map to byte or sbyte, The Name field need a SizeConst attribute, Using the default pack size.

[StructLayout(LayoutKind.Sequential)]
public struct ParameterResponse
{
    public uint Descriptor;
    public uint Value;
    public uint Minimum;
    public uint Maximum;
    public uint Default;
    public ushort Next;
    public ushort Previous;
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 4)]
    public byte[] Units;
    public ushort Multiplier;
    public ushort Divisor;
    public ushort Base;
    public ushort Offset;
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 3)]
    public byte[] Link;
    public byte pad;
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 16)]
    public byte[] Name;
}