通过DllImport调用非托管函数时损坏的堆

我正在使用一个从c#应用程序用C/c++编写的非托管dll。我有兴趣从dll中使用以下函数:

    static void StorePath(const std::string& path, wchar_t *out_path,
     int *out_path_length){
      wcslcpy(out_path, c_str_w(path), *out_path_length);
      *out_path_length = path.size();
     }
    int WINAPI BrowseForDirectory(
     int allow_portable, int allow_online,
      wchar_t *t_directory, int *e_directory_length,
       wchar_t *m_directory, int *m_directory_length){
     .
     .
     . //initializing new forms and checking product keys
    StorePath(form->SelectedEDirectory().TopDir(), e_directory,
     e_directory_length);
    StorePath(form->SelectedMDirectory(), m_directory,
     m_directory_length);
    }

头文件:

    #if defined(_WIN32) && !BUILD_WITHOUT_DLLS &&!defined(ECLIPSE_CBUILDER_WORKAROUNDS)
    # if BUILDING_EXPORT_LIBRARY
    #  define EXPORT_DLL __declspec(dllexport)
    # else
    #  define EXPORT_DLL __declspec(dllimport)
    # endif
    #else
    #  define EXPORT_DLL
    #endif
    extern "C" {
        int WINAPI BrowseForDirectory(
         int allow_portable, int allow_online,
          wchar_t *t_directory, int *e_directory_length,
           wchar_t *m_directory, int *m_directory_length)
    }

然后，我尝试在我自己管理的c#类库中调用这个函数，方法如下:

    [DllImport("MyDLL.dll", CharSet = CharSet.Ansi)]
    public static extern int BrowseForDirectory(Int32 allowOnline, 
     Int32 allowPortable,
      [MarshalAs(UnmanagedType.LPStr)] StringBuilder eDirectory, 
       ref Int32 eDirLength, 
        [MarshalAs(UnmanagedType.LPStr)] StringBuilder mDirectory, 
         ref Int32 mDirLength);

最后，我试图在c#应用程序中使用它，通过调用它:

    var eDir = new StringBuilder(260);
    var mDir = new StringBuilder(260);
    var eDirLength = eDir.Length;
    var mDirLength = mDir.Length;
    try
    {
        var result = Viewer.BrowseForDirectory(1, 1, eDir, 
         ref eDirLength, mDir, ref mDirLength);
    }
    catch(Exception ex)
    {
        MessageBox.Show(ex.ToString());
    }

然而，我得到一个堆损坏，但现在我的应用程序退出，因为status_stack_buffer_overflow——关于嵌入的断点。更改c++代码不是一种选择。我有合适的参考文献和程序集。

我做错了什么?

[DllImport("MyDLL.dll", CharSet = CharSet.Unicode)]
public static extern int BrowseForDirectory(
    int allowOnline, 
    int allowPortable,
    StringBuilder eDirectory, 
    ref int eDirLength, 
    StringBuilder mDirectory, 
    ref int mDirLength
);