DateTimeOffset Error: UTC offset of local dateTime does not match the offset argument

问：

I'm trying to create a small method that converts the time from one timezone to another. I thought it would be simple enough, but when I deploy it I get this error The UTC Offset of the local dateTime parameter does not match the offset argument. My guess is that it's because the server is not in the same timezone as the user which is not helpful since this would be used from around the world.

public object ConvertDate(DateTime inputTime, string fromOffset, string toZone)
{
    var fromTimeOffset = new TimeSpan(0, - int.Parse(fromOffset), 0);
    var to = TimeZoneInfo.FindSystemTimeZoneById(toZone);
    var offset = new DateTimeOffset(inputTime, fromTimeOffset);
    var destination = TimeZoneInfo.ConvertTime(offset, to); 
    return destination.DateTime;
}

Where fromOffset is a number, converted to timespan from the users timezone and toZone is the name of the zone we're converting to. The error occurs on this line var offset = new DateTimeOffset(inputTime, fromTimeOffset);

Any ideas on how to get this working?

答：

See the documentation for why the exception is being thrown:

ArgumentException: dateTime.Kind equals Local and offset does not equal the offset of the system's local time zone.

The DateTime argument that you receive has its Kind property set to Local. The simplest way around this problem is to set the Kind to Unspecified.

public object ConvertDate(DateTime inputTime, string fromOffset, string toZone)
{
    // Ensure that the given date and time is not a specific kind.
    inputTime = DateTime.SpecifyKind(inputTime, DateTimeKind.Unspecified);

    var fromTimeOffset = new TimeSpan(0, - int.Parse(fromOffset), 0);
    var to = TimeZoneInfo.FindSystemTimeZoneById(toZone);
    var offset = new DateTimeOffset(inputTime, fromTimeOffset);
    var destination = TimeZoneInfo.ConvertTime(offset, to); 
    return destination.DateTime;
}

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