DLL未在visual studio 2013 VB代码中导出字符串

我正在用VB写一个小应用程序。NET,到目前为止,我编写了以下代码:

Public Class MainMenu

    Private Declare Function Version_Get Lib "mypath/mydll.dll" () As String   

    ' Before anyone asks, yes, the DLL is present in the mypath folder

    Private Sub MainMenu_Load(sender As Object, e As EventArgs) Handles Me.Load

        Dim Temp As String
        Dim Dummy As Integer

        On Error GoTo Handler
        Temp = Version_Get
        Dummy = 1 ' This line is never reached in debug mode

Handler:
        If Not IsNothing(Err.GetException()) Then
            MsgBox("Error " & Str(Err.Number) & " generated by the application " & Err.Source & ControlChars.CrLf & Err.Description, vbCritical, "Error")
            End
        End If

    End Sub

End Class

BSTR (这当然是 extern "C"

文件h

#ifdef EVALFUNC_EXPORTS
#define EVALFUNC_API __declspec(dllexport)
#else
#define EVALFUNC_API __declspec(dllimport)
#endif

extern "C"
{
    EVALFUNC_API BSTR __stdcall Version_Get();
}

BSTR __stdcall Version_Get()
{
    CRegKey Key;
    CString sValue;
    BSTR Str;

    LONG nA = Key.Open(HKEY_LOCAL_MACHINE, _T("SOFTWARE\\my Software"), KEY_READ);

    // Before anyone asks, yes, the application is present in the system

    ULONG nValueLength = 0;
    LONG nB = Key.QueryStringValue(_T("Version"), NULL, &nValueLength);

    if (nValueLength > 0) LONG nC = Key.QueryStringValue(_T("Version"), sValue.GetBufferSetLength(nValueLength - 1), &nValueLength);    

    Str = sValue.AllocSysString();
    return Str;
}

Version_Get 使我的代码在没有任何错误的情况下崩溃(the MainMenu

我用相同的声明在另一个VB环境(Excel)上尝试了DLL。

Private Declare Function Version_Get Lib "mypath/mydll.dll" () As String

在这种情况下,字符串变量填充了正确的文本。

我做错了什么?