Probably IllegalStateException. From what I read about InvalidOperationException: “The exception that is thrown when a method call is invalid for the object’s current state.” For IllegalStateException: “Signals that a method has been invoked at an illegal or inappropriate time. In other words, the Java environment or Java application is not in an appropriate state for … Read more
The MSDN only has one bit of guidance on this precise topic, on NotSupportedException: For scenarios where it is sometimes possible for the object to perform the requested operation, and the object state determines whether the operation can be performed, see InvalidOperationException. What follows is purely my own interpretation of the rule: If the object’s … Read more
You should change the line this.MyDateTime = myNewDT.MyDateTime.Value; to just this.MyDateTime = myNewDT.MyDateTime; The exception you were receiving was thrown in the .Value property of the Nullable DateTime, as it is required to return a DateTime (since that’s what the contract for .Value states), but it can’t do so because there’s no DateTime to return, … Read more