Getting the Time with TimeProvider

Getting the Time the Traditional Way

We usually use DateTime.Now and DateTimeOffset.Now to get the current time, but code written this way is hard to test: the time depends on the system clock, which is difficult to control and reproduce — the only way to change it is to change the system time.

var now1 = DateTime.Now;
var nowUtc1 = DateTime.UtcNow;

var now2 = DateTimeOffset.Now;
var nowUtc2 = DateTimeOffset.UtcNow;

The New TimeProvider Type

To solve the problems above, .NET 8 introduced the TimeProvider type, which can be used to get the time and makes it easy to control the time in tests.

var now = TimeProvider.System.GetLocalNow();
var nowUtc = TimeProvider.System.GetUtcNow();

Overriding TimeProvider to Simulate the Time

We can override the TimeProvider type to simulate the time, which makes testing easier.

public class MyTimeProvider : TimeProvider
{
    public override DateTimeOffset GetUtcNow() => DateTimeOffset.UtcNow;
}

Dependency Injection of a TimeProvider Implementation

The default implementation, TimeProvider.System, uses the system time.

builder.Services.AddSingleton(TimeProvider.System);

Inject MyTimeProvider to use a custom time source.

builder.Services.AddSingleton<TimeProvider, MyTimeProvider>();

Code That Uses TimeProvider

public class MyService(TimeProvider timeProvider)
{

    public void DoSomething()
    {
        var now = timeProvider.GetLocalNow();
        var nowUtc = timeProvider.GetUtcNow();
    }
}

A demonstration of using TimeProvider in the Zero framework.

Unit Testing Time-Dependent Code

Microsoft.Extensions.TimeProvider.Testing