CODEWITHSUNDEEP
c#
Jane wang
Jane wang

Reputation: 308

How to get rid of NullReferenceException error

I get this error NullReferenceException was unhandled by user code. The error occurs on this line

PropertyChanged(this, new PropertyChangedEventArgs("AboveAircraft"));

I tried if( this != null) and it still got the error. How do I get rid of it?

The code looks like this:

public int AboveAircraft
{
        get { return _above; }
        set
        {
            if (SetProperty(ref _above, value, "AboveAircraft") && _updateModel)
            {
                if (Model.AltitudeBand == null)
                {
                    Model.AltitudeBand = new AltitudeBand();
                }

                if (this != null && AboveAircraft != null)
                {
                    PropertyChanged(this, new PropertyChangedEventArgs("AboveAircraft"));
                    if (_above < _below)
                    {
                        BelowAircraft = _above;
                    }
                }

                Model.AltitudeBand .Above = new AltitudeBandLimit() { Unit = AltitudeUnit.Foot, Value = _above };
            }
        }
}

Upvotes: 2

Views: 467

Answers (1)

ChrisF
ChrisF

Reputation: 137188

You need to check if PropertyChanged is null:

if (PropertyChanged != null)
{
    PropertyChanged(this, new PropertyChangedEventArgs("AboveAircraft"));
}

It will only be not null if there is at least one handler registered elsewhere.

Upvotes: 6

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