打开文件：GetOpenFileName 为什么老是运行出错？求教高手！

[WindFlowFly]

GetSystemDirectory(szDirName,sizeof(szDirName));
szFile[0]='\0';
cbString=LoadStringg_hInstance,IDS_FILTERSTRING,szFilter,sizeofszFilter));
chReplace=szFilter[cbString-1];
for (i=0;szFilter[i]!='\0';i++)
{
if (szFilter[i]==chReplace)
szFilter[i]='\0';
}


OFile.lStructSize=sizeof(OPENFILENAME)*2;
OFile.hwndOwner=g_hWnd;
OFile.lpstrFilter=szFilter;
OFile.nFilterIndex=1;
OFile.lpstrFile=szFile;
OFile.nMaxFile=sizeof(szFile);

OFile.lpstrFileTitle =szFileTitle;
OFile.nMaxFileTitle=sizeof(szFileTitle);
OFile.hInstance=g_hInstance;
OFile.lpstrInitialDir=szDirName;
OFile.Flags =OFN_SHOWHELP | OFN_PATHMUSTEXIST | OFN_FILEMUSTEXIST;
er=GetOpenFileName(&OFile);