Question

In this event handler:

        public static void geolocator_PositionChanged(Geolocator sender, PositionChangedEventArgs args)
        {
            DateTimeOffset timeStampUTC = args.Position.Coordinate.Timestamp.ToUniversalTime();
            DateTimeOffset timeStampLocal = timeStampUTC.LocalDateTime;
            DateTimeOffset dateTimeStampUTC = timeStampUTC.DateTime;
            RecordLocation(args.Position.Coordinate.Latitude, args.Position.Coordinate.Longitude,    
            args.Position.CivicAddress.City, args.Position.CivicAddress.State, dateTimeStampUTC, timeStampLocal);
        }

…I’m getting a Null Reference Exception because args.Position.CivicAddress is null (the rest of the args passed to RecordLocation() are valid). I reckon sometimes Position will be null, and sometimes it won’t. What can I do to let the times when no City or State is found pass through unabated? I tried to make those strings in RecordLocation()‘s definition nullable, but that won’t compile.

Do I need to check CivicAddress for null and create an overloaded version of my RecordLocation() method, or is there another way to handle this?

Answer 1

What can I do to let the times when no City or State is found pass through unabated?

You just need to check it. For example:

if (args.Position != null && args.Position.CivicAddress != null)
{
    // Now you can use args.Position.CivicAddress.State safely
}

If you want to do lots of things with args.Position, you quite possibly want one “outer” if statement – quite possibly with a local variable to simplify things:

var position = args.Position;
if (position != null)
{
    if (position.CivicAddress != null)
    {
        // Use properties of position.CivicAddress
    }
    // Assuming Coordinate is nullable to start with, of course...
    if (position.Coordinate != null)
    {
        // ...
    }
}