C++怎样把ASCII编码转换成Unicode?

//sPath是二进制的编码，wtext是转换后的Unicode码

int len=MultiByteToWideChar(CP_ACP, 0, (LPCSTR)sPath, -1, NULL,0);

WCHAR* wtext = new WCHAR[len+1];
 MultiByteToWideChar(CP_ACP, 0, sPath, -1, wtext, len);