Hi Dan,
Thanks. You are right that I was generating 32 bit DLL since I was using "Developer Command Prompt"
However, I have just tried to re-compile the DLL using X64 Native Tools Command Prompt for VS 2019. After generating DLL, I also used command 'dumpbin' to verify it is is 64 bit DLL. As I load FeRB.x1t into x1t, the x1t program crashed (window disappeared) without giving any error information. Need help on this. FYI, my Windows OS is x64.
Tao