TimeProvider Analyzers

Roslyn analyzers that encourage use of TimeProvider over static date/time properties like DateTime.Now and DateTimeOffset.UtcNow, improving testability in .NET applications.

Installation

Install the NuGet package as a development dependency:

dotnet add package TimeProviderAnalyzers

Rules

TPA0001: Use TimeProvider instead of static property (Info)

Raised when a static date/time property is used and no TimeProvider is in scope. The fix adds a TimeProvider parameter to the enclosing method and replaces the static access.

public void DoSomething()
{
    // TPA0001: Use a method on a TimeProvider instead of the static property 'DateTime.Now'
    var now = DateTime.Now;
}

Fix — adds a TimeProvider parameter:

public void DoSomething(TimeProvider timeProvider)
{
    var now = timeProvider.GetLocalNow().DateTime;
}

---

TPA0002: Use the available TimeProvider instead of a static property (Warning)

Raised when a static date/time property is used and a TimeProvider is already in scope (as a parameter, local variable, field, or property). The fix replaces the static access with the appropriate TimeProvider call.

public sealed class MyService
{
    private readonly TimeProvider _timeProvider;

    public MyService(TimeProvider timeProvider) => _timeProvider = timeProvider;

    public void DoSomething()
    {
        // TPA0002: Use a method on the available TimeProvider '_timeProvider' instead of the static property 'DateTime.Now'
        var now = DateTime.Now;
    }
}

Fix — uses the available TimeProvider:

var now = _timeProvider.GetLocalNow().DateTime;

---

TPA0003: Forward the available TimeProvider to methods that accept one (Warning)

Raised when a method is called without a TimeProvider argument, a TimeProvider is in scope, and an overload of that method exists that accepts a TimeProvider.

public void Schedule(TimeProvider timeProvider)
{
    // TPA0003: Pass the available TimeProvider 'timeProvider' to 'Delay'
    Task.Delay(TimeSpan.FromSeconds(1));
}

Fix — passes the available TimeProvider:

Task.Delay(TimeSpan.FromSeconds(1), timeProvider);

---

Static property replacements

Static property	TimeProvider equivalent
DateTime.Now	timeProvider.GetLocalNow().DateTime
DateTime.UtcNow	timeProvider.GetUtcNow().UtcDateTime
DateTime.Today	timeProvider.GetLocalNow().Date
DateTimeOffset.Now	timeProvider.GetLocalNow()
DateTimeOffset.UtcNow	timeProvider.GetUtcNow()