Question

On my application i assign a DateTime.Now to a new DateTime. then i assign it to a value and write it to the database. But then when i get it back from the database and compare the variable to the new datetime assigned earlier it differs with a couple of milliseconds.

Anyone has an idea why this happens?

E.g.

DateTime var1 = DateTime.Now;
Object1.DateTime = var1;

Database.SaveObject = var1

Object2 = Database.FindObjectById(objectId);

Assert.AreEqual(var1, Object2.DateTime);

Answer 1

This is most likely an issue with the precision of DB’s datetime column: it does not have enough accuracy to store the time up to a millisecond. When you use datetime, the time portion is rounded to increments of .000, .003, or .007 seconds.

Switching column’s type to datetime2 should help, because its resolution is 100 nanoseconds.