How to get “INSTALLED” property in Custom Action DLL (MSI/Wix)?

Question

In my custom DLL I need to check if product is being installed or uninstalled, and hence need to get value of "INSTALLED" property (just like in WiX script). Here is what I am doing in C++ DLL:

WCHAR propValue[MAX_PATH];
DWORD propValLen = MAX_PATH;
// MSIHANDLE msiHandle; 
MsiGetProperty(msiHandle, L"INSTALLED", propValue, &propValLen);
propValue[propValLen] = 0;

But the outcome is always an empty string (for both installation and uninstallation)! How check if product is being installed or uninstalled?

Answer 1

属性名称区分大小写，“已安装”： https : //msdn.microsoft.com/zh-cn/library/windows/desktop/aa369297(v=vs.85).aspx