C# array within a struct

Want to do this: (EDIT: bad sample code, ignore and skip below)

struct RECORD {
    char[] name = new char[16];
    int dt1;
}
struct BLOCK {
    char[] version = new char[4];
    int  field1;
    int  field2;
    RECORD[] records = new RECORD[15];
    char[] filler1 = new char[24];
}

But being unable to declare array sizes in struct, how do I reconfigure this?

EDIT: The reason for the layout is I'm using BinaryReader to read a file written with C structs. Using BinaryReader, and a C# struct union (FieldOffset(0)), I'm wanting to load the header as a byte array, then read it as it was intended originally.

[StructLayout(LayoutKind.Sequential)]
unsafe struct headerLayout
{
    [FieldOffset(0)]
    char[] version = new char[4];
    int fileOsn;
    int fileDsn;
    // and other fields, some with arrays of simple types
}

[StructLayout(LayoutKind.Explicit)]
struct headerUnion                  // 2048 bytes in header
{
    [FieldOffset(0)]
    public byte[] headerBytes;      // for BinaryReader
    [FieldOffset(0)]
    public headerLayout header;     // for field recognition
}