Visual Basic 和 C++ 的 DLL 之间传递一个字符串的方法

.cpp

  void __stdcall FillString(LPSTR pszString, LONG cSize)
{
         // Create a temp buffer with our string
         char buffer[] = "Hello from the C DLL!";

         // Copy our temp string to pszString
         // but check the size to make sure we have a buffer
         // big enough to hold the entire string.
         if (cSize > strlen(buffer))
            strcpy(pszString, buffer);
}

.def(不可或缺的，之前一直少了这个，报很多奇怪的问题)

LIBRARY StrSamp
      DESCRIPTION 'Microsoft KB Sample DLL'
      EXPORTS
         DisplayStringByVal
         DisplayStringByRef
         FillString
         InStrRev

VB

Private Declare Sub FillString Lib "StrSamp.dll" _
         (ByVal sMyString As String, ByVal cBufferSize As Long)

Private Sub Command2_Click()
         Dim sFillTest As String

         sFillTest = Space$(260)
         FillString sFillTest, 260
         MsgBox Trim$(sFillTest), vbInformation, "Fill String"

End Sub

from:

http://support.microsoft.com/kb/187912