I would like to use a managed dll for ArcMap and background geoprocessing (64-bit). I registered the dll by using the methods described in 43712 - ESRIRegAsm.exe Error: Registration Failed. Could not load file or assembly and 40735 - Register function tools (DLL) for both Desktop and 64-bit Background Processing. However, i got the problem in step 5 (ESRIRegAsm.exe C:\xxx\xxxx.dll /regfile:xx.reg). I found that ESRIRegAsm.exe cannot generate any register file (xx.reg) in 10.3 under win7(64-bit) but successfully generate in 10.2 under win server 2008(64-bit). I used the parameter ESRIRegAsm /e to get the error message but it just showed "Generation of reg file failed (/regfile option)." Did I get anything wrong for dll registration for 10.3 under win 7 (64-bit)? or It is a bug for 10.3?