[VB.NET]求教:vb.net调用MFC DLL问题

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求教:vb.net调用MFC DLL问题
vb.net:
Public Declare Function fx Lib "Analyze.dll " Alias "fenxi " (ByVal szFileName As String, ByVal appPath As String) As Integer
调用:
result = fx(pathName, foder)

错误:
未处理的“System.NullReferenceException”类型的异常

其他信息: 未将对象引用设置到对象的实例

在线等待.

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QQ:331069386
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ｖｃ提供的接口类型有问题吧
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CathySun118(斯年) :
兄弟,能不能说得详细点?
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BOOL CAnalyzeApp::fenxi(CString szFileName,CString appPath)
{
//_CrtSetDbgFlag ( _CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF );
BOOL result1;
LONG rnum;
rnum = 0;
AfxMessageBox( "start ");
CAvi1* Avi1=new CAvi1();
result1 = Avi1-> ExtractAVIFrames(szFileName,appPath);
AfxMessageBox( "start1 ");
if (result1 == FALSE)
{
AfxMessageBox(szFileName + "视频文件有损坏! ");
//当做无人处理
return FALSE;
}

AfxMessageBox( "234 ");
Avi1-> OnDetectMinus(appPath);
rnum = Avi1-> lReturnNum;
if (rnum <= 10 )
{
//无人
return FALSE;
}
else
{
//有人
return TRUE;
}

AfxMessageBox( "ok ");
delete Avi1;
return TRUE;
}
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这是vc里的代码
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dll 里 接口函数应定义成
_desc export BOOL CAnalyzeApp::fenxi
我记得是这样。
具体写法网上搜就行
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不好意思,发错了,请高手帮忙啊
int CAnalyzeApp::fenxi(CString szFileName,CString appPath)
{
//_CrtSetDbgFlag ( _CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF );
BOOL result1;
LONG rnum;
rnum = 0;
AfxMessageBox( "start ");
CAvi1* Avi1=new CAvi1();
result1 = Avi1-> ExtractAVIFrames(szFileName,appPath);
AfxMessageBox( "start1 ");
if (result1 == FALSE)
{
AfxMessageBox(szFileName + "视频文件有损坏! ");
//当做无人处理
return 0;
}

AfxMessageBox( "234 ");
Avi1-> OnDetectMinus(appPath);
rnum = Avi1-> lReturnNum;
if (rnum <= 10 )
{
//无人
return 0;
}
else
{
//有人
return 1;
}

//AfxMessageBox( "ok ");
//delete Avi1;
//return TRUE;
}
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CAvi1* Avi1=new CAvi1();
result1 = Avi1-> ExtractAVIFrames(szFileName,appPath);
这里错了?
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你直接用非托管方法吧
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兄弟,能不能说得详细点?

谁有这方面的开发经验,给指条明路啊
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