FUNCTION ReadVariableString(pszBuffer REF PSZ) AS LONG PASCAL

   LOCAL cString2Return      AS STRING
   LOCAL pszLocalBuffer        AS PSZ
   
   LOCAL loBufferLength      AS LONG
   LOCAL lReturnedLength      AS LONG
   LOCAL loStringLength      AS LONG
   LOCAL cString         AS STRING
   
   // longer than 64 Bytes
   // cString2Return   := Replicate(".",256)+"This is aString from a VO-DLL!"
   // smaller than 64 Bytes
   cString2Return   := "This is aString from a VO-DLL!"
   loStringLength   := SLen(cString2Return)
   // necessary to determine buffer length
   // pszLocalBuffer   := PSZ(_CAST,pszBuffer)
   // loBufferLength   := PszLen(pszLocalBuffer)
   loBufferLength   := PszLen(PSZ(_CAST,pszBuffer))
   lReturnedLength   := loBufferLength-(loStringLength+1) // +1 for CHR(0)
   IF lReturnedLength < 0
   
      // Buffer to small
      loStringLength   := loBufferLength-1
      cString       := Left(cString2Return,(loStringLength))

   ELSE // lReturnedLength < 0

      // Buffer size ok:
      cString         := cString2Return
      lReturnedLength   := SLen(cString2Return)
      
   ENDIF // lReturnedLength < 0
   MemCopyString(pszBuffer,cString+CHR(0),loStringLength+1)
   
RETURN lReturnedLength

using System;
using System.Runtime.InteropServices;

class ReadStringFromVoDll
{
    [DllImport(@"D:\!UnderDev\c-Sharp\VarStringfromVo\VarString.dll", CharSet = CharSet.Ansi)]
    public static extern int ReadVariableString(
       [MarshalAs(UnmanagedType.LPStr)]
        ref string cStringFromVo);
    public static void Main()
    {
        System.Console.WriteLine(ReadStringFromVo());
        System.Console.ReadKey();

    }
    public static string ReadStringFromVo()
    {
        // create a small Buffer
        int iBuffLen    = 10;
        string cS = " ".PadRight(10,' ');
        int iResult = ReadVariableString(ref cS);
        if (iResult < 0)
            // Buffer too small
            // greater bigger one and try again
        {
            cS = cS.PadRight(((iResult * -1) + iBuffLen),' ');
            iResult = ReadVariableString(ref cS);
        }
        return cS;
    }
}