Question

I wanted to assign null value to DateTime type in c#, so I used:

public DateTime? LockTime;

When LockTime is not assigned LockTime.Value contains null by default.
I want to be able to change LockTime.Value to null after it has been assigned other value.

Answer 1

No, if LockTime hasn’t been assigned a value, it will be the nullable value by default – so LockTime.Value will throw an exception if you try to access it.

You can’t assign null to LockTime.Value itself, firstly because it’s read-only and secondly because the type of LockTime.Value is the non-nullable DateTime type.

However, you can set the value of the variable to be the null value in several different ways:

LockTime = null; // Probably the most idiomatic way
LockTime = new DateTime?();
LockTime = default(DateTime?);