VB有关指针字符的有关问题

VB有关指针字符的问题.
delphi 中
function StartReadCard(aHandle: THandle; ComPort: PChar; BaudRate: Integer; var Buffer: array of Byte; var DataLength: Integer): boolean; stdcall; external 'ReadCard.dll';

var
  buf: array[0..4] of Byte; 
  i: integer;
  iDateLen: Integer;
  sCommPort: string;
  iCommType: Integer;
  iIDReaderType: Byte;
  iBaudRate: Integer;
  sCardNo: string;
  OriginalCardID:Int64;

  FillChar(buf, 5, 0);
  sCommPort := 'com6';
  iBaudRate := 9600;
  if StartReadCard(Application.Handle, PChar(sCommPort), iBaudRate, buf, iDateLen) then
  ........
  end if

VB中怎么写
Private Declare Function StartReadCard Lib "ReadCard.dll" (ByVal aHandle As Long, ByVal ComPort As String, ByVal BaudRate As Integer, ByRef Buffer As byte , ByRef DataLength As Long) As Boolean

  Dim buf() As byte  
  Dim i As Integer
  Dim iDateLen As Long
  Dim sCommPort As String
  Dim iCommType As Integer
  Dim iIDReaderType As Byte
  Dim iBaudRate As Integer
  Dim sCardNo As String
  Dim OriginalCardID As Long

  sCommPort = "com6"
  iBaudRate = 9600
  ReDim buf(4)
  For i = 0 To UBound(buf)
  buf(i) = "0"
  Next i
  If StartReadCard(App.hInstance, sCommPort, iBaudRate, buf(0), VarPtr(iDateLen)) Then
  ............
  end if

到StartReadCard这,就报内存错误.
帮忙看下,哪有问题

[解决办法]

VB code

Option Explicit'function StartReadCard(aHandle: THandle;'                       ComPort: PChar;'                       BaudRate: Integer;'                       var Buffer:array of Byte;'                       var DataLength: Integer): boolean; stdcall; external 'ReadCard.dll';Private Declare Function StartReadCard Lib "ReadCard.dll" (ByVal aHandle As Long, _                                                           ByVal ComPort As String, _                                                           ByVal BaudRate As Long, _                                                           Buffer() As Byte, _                                                           ByVal DataLength As Long) As BooleanPrivate Sub Form_Load()    Dim buf() As Byte    Dim i As Integer    Dim iDateLen As Long    Dim sCommPort As String    Dim iCommType As Integer    Dim iIDReaderType As Byte    Dim iBaudRate As Integer    Dim sCardNo As String    Dim OriginalCardID As Long        sCommPort = "COM6"    iBaudRate = 9600    ReDim buf(4)    For i = 0 To UBound(buf)        buf(i) = "0"    Next i    If StartReadCard(App.hInstance, sCommPort, iBaudRate, ByVal VarPtr(buf(0)), iDateLen) Then        End IfEnd Sub
[解决办法]
function StartReadCard(aHandle: THandle; ComPort: PChar; BaudRate: Integer; var Buffer: array of Byte; var DataLength: Integer): boolean; stdcall; external 'ReadCard.dll';

试试改成这样：
Private Declare Function StartReadCard Lib "ReadCard.dll" (ByVal aHandle As Long, ByVal ComPort As Byte, ByVal BaudRate As Long, ByRef Buffer As byte , ByRef DataLength As Long) As Boolean
最后一个参数，byval，byref都试试看

[解决办法]
头痛的问题。。。