CODEWITHSUNDEEP
c#
Peyman Tahmasebi
Peyman Tahmasebi

Reputation: 193

Update datetime in Database

Consider this code:

var datetime = DateTime.Now;        
var instantMessage = InstantMassageingManager.GetConverationMessages().FirstOrDefault();
InstantMassageingManager.UpdateConversationMessageReadDateTime(instantMessage.InstantMessageInstanceId, datetime);
var message = InstantMassageingManager.GetMessageById(instantMessage.InstantMessageInstanceId);
Assert.IsTrue(message.ReadDateTime.Value == datetime);

in the first line I get DateTime.Now

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then I update a record in database: UpdateConversationMessageReadDateTime

and get the message again from the database:

enter image description here

Both message.ReadDateTime and datetime has same value but with different Tick.

So my test doesn't pass.

Why do I get different values for tick?

Upvotes: 3

Views: 212

Answers (1)

Jon Skeet
Jon Skeet

Reputation: 1499860

I strongly suspect that the type you're using in the database doesn't have the same level of precision - I suspect it's only accurate to the millisecond.

If you want to round-trip the time, you should truncate your "input" time to the nearest millisecond too. For example:

TimeSpan rounded = TimeSpan.FromMilliseconds(original.Ticks / 10000);

Or for a DateTime:

DateTime rounded = new DateTime(original.Year, original.Month, original.Day,
    original.Hour, original.Minute, original.Second, original.Millisecond,
    original.Kind);

You should also consider whether you really want to take the local time (which depends on the system time zone) or a UTC value. It depends on the context, but it's more frequently appropriate to store UTC values for timestamps, which is what it looks like you've got here.

Upvotes: 7

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