Issue with property setter with an object and toolbox

Question

This code works fine, I can check if a timecode is valid when the property changes its value. But the problem is that I cannot set the value of this property in the toolbox, because of the new ValidTimeCodeEventArgs.

Is there a way to fix this so I could change the value in the toolbox and check if it is correct?

[Browsable(true)]
public event EventHandler<ValidTimeCodeEventArgs> ValidTimeCode;

private string strTimeCode;
[Category("Custom")]
[Browsable(true)]
[DefaultValue(typeof(string), "00:00:00:00")]
public string StrTimeCode {
    get {
        return strTimeCode;
    }
    set {

        if (value != null) {
            ValidTimeCode(this, new ValidTimeCodeEventArgs(IsValidTimeCode(value, FrameRate, IsDropFrame)));
            strTimeCode = value;
            initValue = strTimeCode;
            Invalidate();
        }
    }
}

public class ValidTimeCodeEventArgs : EventArgs {

    public ValidTimeCodeEventArgs(bool isValid) {
        IsValid = isValid;
    }

    public bool IsValid { get; }
}

Answer 1

Your ValidTimeCode event probably doesn't have any subscribers when you try to raise it. Try:

ValidTimeCode?.Invoke(this, new ValidTimeCodeEventArgs(IsValidTimeCode(value, FrameRate, IsDropFrame)));

This basically does a null check on the handler (it's null if no one subscribed to the event), then only raises it if it isn't null. See here for more info.