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c#wpfmvvmobservablecollectioninotifypropertychanged
Cornel Marian
Cornel Marian

Reputation: 2503

How to implement IsDirty on properties that are collections in MVVM pattern with WPF?

How to implement IsDirty mechanism on properties that are collections in MVVM pattern with WPF?

IsDirty is a flag that indicates if the data in the viewmodel has changed and it is used for the save operation.

How to propagate IsDirty ?

Upvotes: 1

Views: 2366

Answers (1)

Gayot Fow
Gayot Fow

Reputation: 8802

You can implement a custom collection along these lines...

 public class MyCollection<T>:ObservableCollection<T>, INotifyPropertyChanged 
    {
        // implementation goes here...
        //
        private bool _isDirty;
        public bool IsDirty
        {
            [DebuggerStepThrough]
            get { return _isDirty; }
            [DebuggerStepThrough]
            set
            {
                if (value != _isDirty)
                {
                    _isDirty = value;
                    OnPropertyChanged("IsDirty");
                }
            }
        }
        #region INotifyPropertyChanged Implementation
        public event PropertyChangedEventHandler PropertyChanged;
        protected virtual void OnPropertyChanged(string name)
        {
            var handler = System.Threading.Interlocked.CompareExchange(ref PropertyChanged, null, null);
            if (handler != null)
            {
                handler(this, new PropertyChangedEventArgs(name));
            }
        }
        #endregion
    }

And declare your collections like this...

MyCollection<string> SomeStrings = new MyCollection<string>();
SomeStrings.Add("hello world");
SomeStrings.IsDirty = true;

This approach lets you enjoy the benefits of ObservableCollection and simultaneously allows you to append a property of interest. If your Vm's do not use ObservableCollection, you can inherit from List of T using the same pattern.

Upvotes: 1

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