[API Proposal]: TryFindSystemTimeZoneById

[danielchalmers]

Background and motivation

The method for finding a timezone by a string, TimeZoneInfo.FindSystemTimeZoneById, throws a TimeZoneNotFoundException if it can't find one. AFAIK there isn't a non-throwing method in the runtime.

I use a version of the method below to attempt to find a time zone or fallback to local time:

public static TimeZoneInfo GetTimeZone() =>
DateTimeUtil.TryGetTimeZoneById(Settings.Default.TimeZone, out var timeZoneInfo) ? timeZoneInfo : TimeZoneInfo.Local;

This is of course still possible using the current method but it's not as clean IMO.

API Proposal

namespace System
{
    public class TimeZoneInfo
    {
        public static bool TryFindSystemTimeZoneById(string id, out TimeZoneInfo timeZoneInfo)
        {
            try
            {
                timeZoneInfo = TimeZoneInfo.FindSystemTimeZoneById(id);
                return true;
            }
            catch (TimeZoneNotFoundException)
            {
                timeZoneInfo = null;
                return false;
            }
        }
    }
}

API Usage

// Ask user for timezone.
Console.WriteLine("Enter a timezone");
var tz = Console.ReadLine();

// Validate.
if(TimeZoneInfo.TryFindSystemTimeZoneById(tz, out var tzInfo))
    Console.WriteLine("Found timezone");
else
    Console.WriteLine("Invalid timezone");

// Ask user for timezone.
Console.WriteLine("Enter a timezone");
var tz = Console.ReadLine();

// Try to find timezone or fall back to local time.
var finalTimeZone = TimeZoneInfo.TryFindTimeZoneById(tz, out var tzInfo) ? tzInfo : TimeZoneInfo.Local;
Console.WriteLine("Using " + finalTimeZone.DisplayName);

Alternative Designs

No response

Risks

No response

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[ghost]

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Issue Details

---

Background and motivation

The method for finding a timezone by a string (TimeZoneInfo.FindSystemTimeZoneById) throws a TimeZoneNotFoundException if it can't find one and AFAIK there isn't a non-throwing method for it in the runtime.

I use a version of the method below to attempt to find a timezone from a string, and fallback to local time if one's not found:

public static TimeZoneInfo GetTimeZone() =>
DateTimeUtil.TryGetTimeZoneById(Settings.Default.TimeZone, out var timeZoneInfo) ? timeZoneInfo : TimeZoneInfo.Local;

This is of course still possible using the current method but it's less clean (IMO).

API Proposal

namespace System
{
    public class TimeZoneInfo
    {
        public static bool TryFindSystemTimeZoneById(string id, out TimeZoneInfo timeZoneInfo)
        {
            try
            {
                timeZoneInfo = TimeZoneInfo.FindSystemTimeZoneById(id);
                return true;
            }
            catch (TimeZoneNotFoundException)
            {
                timeZoneInfo = null;
                return false;
            }
        }
    }
}

API Usage

// Ask user for timezone
Console.WriteLine("Enter a timezone");
var tz = Console.ReadLine();

// Validate
if(TimeZoneInfo.TryFindSystemTimeZoneById(tz, out var tzInfo))
    Console.WriteLine("Using entered timezone");
else
    Console.WriteLine("Invalid timezone");

// Ask user for timezone
Console.WriteLine("Enter a timezone");
var tz = Console.ReadLine();

// Try to find timezone or fall back to local time
var finalTimeZone = TimeZoneInfo.TryFindTimeZoneById(tz, out var tzInfo) ? tzInfo : TimeZoneInfo.Local;
Console.WriteLine("Using " + finalTimeZone.DisplayName);

Alternative Designs

No response

Risks

Same risks as adding any new API

Author:	danielchalmers
Assignees:	-
Labels:	api-suggestion, area-System.Runtime, untriaged
Milestone:	-

[pinkfloydx33]

I implemented the very same workaround this past week. I was surprised there isnt a Try-/non-throwing variant. We accept the TZ name as user-provided input so can't rely on it being valid. The workaround isn't that bad, but it'd be nice to have a way to do a lookup without the exception.

[tannergooding]

CC. @tarekgh, could you provide insight into whether this is something we should look at providing?

[tarekgh]

@tannergooding this is a nice to have helper method but not necessary blocking any scenario. It is easy to have the apps adding extension method that does that.

[tannergooding]

Do you think this is in the right shape for us to mark api-ready-for-review then or are there any other concerns with the current proposal?

[tarekgh]

The API shape looks good to me.

[bartonjs]

Video

Looks good as proposed (ignoring that the body says to do a try/catch).

namespace System
{
    public class TimeZoneInfo
    {
        public static bool TryFindSystemTimeZoneById(string id, out TimeZoneInfo timeZoneInfo);
    }
}