When attempting to install the Microsoft Azure Active Directory Sync Services tool (DirSync), you may receive this error: A constraint violation occurred
Rather unhelpful error code. Luckily, there is a really easy fix for this. Log off and then log back on again. You might also want to verify that the system does not have a pending reboot, if so then reboot instead. Verify you have both Microsoft .NET Framework 3.5 and 4.5 installed and configured on the machine.
If you have to configure DirSync again from a fresh install, uncheck the box “Start Configuration Wizard now” to avoid this issue. Log off and then log back in. This should take care of the error entirely.