关于调用delphi写的DLL的问题，纠结啊

Question

delphi的接口方法是这样的：
procedure GetLastCashCardBalance(Card:PTMemberCashCard_Rd);stdcall;
begin
  Card.iMemberID := FPosService.LastCashCardBalance.iMemberID;
  SetPChar(@Card.sMemberCode[0], FPosService.LastCashCardBalance.sMemberCode);
  DateTimeToSystemTime(FPosService.LastCashCardBalance.dateValid,Card.dateValid);
  Card.mBalance := FPosService.LastCashCardBalance.mBalance;
  Card.mBottom := FPosService.LastCashCardBalance.mBottom;
  Card.mAmount := FPosService.LastCashCardBalance.mAmount;
end;
其中PTMemberCashCard_Rd是这么定义的
 { TMemberCashCard = class
    iMemberID: integer;
    sMemberCode: string;
    dateValid: TDate;
    mBalance: TMoney;
    mBottom: TMoney;
    mAmount: TMoney;
    bRecycle: boolean;
  public
    procedure Clear;
  end; }  TMemberCashCard_Rd =  Record
    iMemberID: integer;
    sMemberCode: Array[0..255] of char;
    dateValid: SystemTime;
    mBalance: integer;
    mBottom: integer;
    mAmount: integer;
    bRecycle: Integer;
  end;  PTMemberCashCard_Rd =^TMemberCashCard_Rd;我在C#里的调用方法如下
定义结构
 public struct LastCashCardBalance
        {
            public Int32 iMemberID;
            public string  sMemberCode;
            public DateTime dateValid;
            public Int32 mBalance;
            public Int32 mBottom;
            public Int32 mAmount;
            public Int32 bRecycle;
        }  [DllImport("CardInterface.dll", CallingConvention = CallingConvention.StdCall, CharSet = CharSet.Ansi)]
  public static extern void GetLastCashCardBalance( LastCashCardBalance s);调用：
LastCashCardBalance lst = new LastCashCardBalance();
 GetLastCashCardBalance(lst);
提示尝试读取或写入受保护的内存。这通常指示其他内存已损坏。求大侠帮忙看看是什么原因啊

Answer 1

我把 LastCashCardBalance 改成这样，传进去调用，不报错，但是得不到值
public class LastCashCardBalance
    {
        private Int32 MemberID;
        private char[] MemberCode=new char[256];
        private DateTime dateValid;
        private Int32 Balance;
        private Int32 Bottom;
        private Int32 Amount;
        private Int32 Recycle;        public Int32 iMemberID
        {
            set { MemberID = value; }
            get { return MemberID; }
        }
        public char[] sMemberCode
        {
            set { MemberCode = value; }
            get { return MemberCode; }
        }        public DateTime sdateValid
        {
            set { dateValid = value; }
            get { return dateValid; }
        }
        public Int32 iBalance
        {
            set { Balance = value; }
            get { return Balance; }
        }
        public Int32 iBottom
        {
            set { Bottom = value; }
            get { return Bottom; }
        }
        public Int32 iAmount
        {
            set { Amount = value; }
            get { return Amount; }
        }
        public Int32 iRecycle
        {
            set { Recycle = value; }
            get { return Recycle; }
        }    }

Answer 2

ref LastCashCardBalance s另外delphi中不要用string类型，改为array of byte 或 array of char

Answer 3

谢谢前辈，我改成这样
 public struct LastCashCardBalance
        {
            public Int32 iMemberID;
            [MarshalAs(UnmanagedType.ByValArray, SizeConst =256)]
            public char[] sMemberCode;
            public DateTime  dateValid;
            public Int32 mBalance;
            public Int32 mBottom;
            public Int32 mAmount;
            public Int32 bRecycle;
        }    [DllImport("CardInterface.dll", CallingConvention = CallingConvention.StdCall, CharSet = CharSet.Ansi)]
   public static extern void GetLastCashCardBalance(ref LastCashCardBalance s);调用：
LastCashCardBalance lst = new LastCashCardBalance();
  GetLastCashCardBalance(ref lst);
可以调用成功了，但是返回值除了iMemberID是正确的，其他都不对，要么是空，要么是0