Why am I getting an exception with the following code?

Question

I have a property defined in an interface as:

 Boolean IsBusy { get; }

It is implemented in the class as:

private Boolean _isBusy = false;
public Boolean IsBusy
    {
        get
        {
            return this._isBusy;
        }

        private set
        {
            if (this._isBusy != value)
            {
                this._isBusy = value;
                this.OnPropertyChanged("IsBusy");
            }
        }
    }

Then when I run the app, I always get following kind of error when check IsBusy value in constructor:

'IsBusy' threw an exception of type 'System.NullReferenceException' bool {System.NullReferenceException}

I can't figure it out. If I change all Boolean to bool, get same error.

How can I fix it?

Can you privide fragment of your constructor, where you call IsBusy? — st78, Nov 05 '10 at 18:14

score 10 · Answer 1 · answered Nov 05 '10 at 18:00

You fix it by checking whether OnPropertyChanged is null before calling it, assuming OnPropertyChanged is an event or a delegate variable (you haven't made this clear). This has nothing to do with bool or Boolean, which are equivalent (assuming that Boolean is resolved to System.Boolean).

I can't see any other reason it would throw NullReferenceException - although it would really help you could clarify whether you were calling the getter or the setter at the time it threw the exception. A short but complete example would be even more helpful.

score 1 · Answer 2 · answered Nov 05 '10 at 17:59

1

bool is just a syntax shortcut for Boolean

answered Nov 05 '10 at 17:59

Liviu Mandras

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score 1 · Answer 3 · answered Nov 05 '10 at 17:59

1

Both bool and Boolean evaluate to the same thing in compilation.

answered Nov 05 '10 at 17:59

Jeremy Elbourn

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score 1 · Answer 4 · answered Nov 05 '10 at 18:00

1

none. Boolean is what the .net CLI uses to represent a true/false value. bool is what c# uses.

answered Nov 05 '10 at 18:00

jasper

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score 1 · Answer 5 · answered Nov 05 '10 at 18:00

1

bool is a C# alias for the struct System.Boolean. They are the same.
Your problem probably is that this.OnPropertyChanged is unassigned. This is completely unrelated to bool vs Boolean.

answered Nov 05 '10 at 18:00

rsenna

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score 1 · Answer 6 · edited May 23 '17 at 12:29

1

C# contains aliase for all the native types. String for string, Int32 for int, etc. there is no difference with which you use:

String vs string in C#

Boolean cannot be NULL, so you are likely getting an error because of something in OnPropertyChanged.

edited May 23 '17 at 12:29

Community

1
1

answered Nov 05 '10 at 18:00

GendoIkari

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score 0 · Answer 7 · answered Nov 05 '10 at 18:03

0

The bool keyword is just a type alias for the Boolean keyword.

Just the same as int is an alias for Int32.

answered Nov 05 '10 at 18:03

Why am I getting an exception with the following code?

7 Answers7