ElapsedEventArgs doesn't have a public constructor

[ashelleyPurdue]

System.Timers.ElapsedEventArgs doesn't have a public constructor, despite just being a data class containing one property. This makes it unnecessarily awkward to write a mock for something that uses an ElapsedEventHandler, because you need to use a workaround just to create this one object.

It's impossible to solve this by subclassing ElapsedEventArgs, because the SignalTime property is read-only and therefore cannot be set by your constructor.

[vcsjones]

To put this in terms of a concrete API proposal:

namespace System.Timers
{
    public class ElapsedEventArgs : EventArgs
    {
+       public ElapsedEventArgs(DateTime signalTime);
    }
}

[ericstj]

This seems like a reasonable request.

[ericstj]

At this point it's too late for this to go into 6.0.0.

[JasonDWilson]

Did this make it into 7? It really is a pain

[vcsjones]

Did this make it into 7?

It has not. Since this issue was originally filed, #44853 changed the constructor to take a DateTime instead of a long. So now it really is just a matter of making the constructor public.

@dotnet/area-system-componentmodel this seems like an easy enough one I can take care of if we want to put this through API review. Proposal at #31204 (comment)

[terrajobst]

Video

• Currently people can't derive from this type (because there are no public constructors), we should seal it
• Do we need to add any argument validation?

namespace System.Timers;

public sealed class ElapsedEventArgs : EventArgs
{
    public ElapsedEventArgs(DateTime signalTime);
}

[TheMaximum]

I'd be interested to make this change. A quick look at the existing class shows there's already an internal constructor taking a DateTime argument (see below), wouldn't it be sufficient to change this to public (and seal the class)?

runtime/src/libraries/System.ComponentModel.TypeConverter/src/System/Timers/ElapsedEventArgs.cs

Lines 6 to 14 in 4d2ef11

	public class ElapsedEventArgs : EventArgs
	{
	internal ElapsedEventArgs(DateTime localTime)
	{
	SignalTime = localTime;
	}
	public DateTime SignalTime { get; }
	}

[vcsjones]

wouldn't it be sufficient to change this to public (and seal the class)?

Yep.

Do we need to add any argument validation?

We discussed this further in the API review and we didn't think of any reasonable validations that should be applied as the input.