c# class written in simple terms for wpf mvvm

Question

I've come across an example tutorial online and saw a property for a class written like this for a wpf project. I was wondering what this would translate to in simpler terms since i've never seen a class written like this before.

Is the translation i attempted correct? Meaning is it doing the same thing the tutorial class is doing?

Tutorial Class

public ObservableCollection<string> Directories
{
    get { return Get<ObservableCollection<string>>(); }
    set { Set(value); }
}

My attempted guess at what it would be written as

private ObservableCollection<string> _directories; 
public ObservableCollection<string> Directories
{
    get
    {
        return this._directories;
    }

    set
    {
        this._directories= value;
    }
}

What is your actual question? – rory.ap Oct 20 '15 at 11:29 — rory.ap, Oct 20 '15 at 11:29
is my translation of the tutorial class correct? – JokerMartini Oct 20 '15 at 11:30 — JokerMartini, Oct 20 '15 at 11:30
Could you post the tutorial link? – Jose Oct 20 '15 at 11:33 — Jose, Oct 20 '15 at 11:33

Mark Feldman · Accepted Answer · 2015-10-20T23:14:12.440

We'd have to see the Get/Set implementations to answer this question properly but my guess is it's been done to improve code readability. There are two things you often see in MVVM properties: auto-initialization in the getter and property change notification in the setter...

    private ObservableCollection<string> _directories;
    public ObservableCollection<string> Directories
    {
        get
        {
            // auto-initialize
            if (this._directories == null)
                this._directories = new ObservableCollection<string>();
            return this._directories;
        }
        set
        {
            this._directories = value;
            RaisePropertyChanged("Directories"); // INPC
        }
    }

This leads to a lot of code bloat if you're doing it for a large number of properties. My guess is the Set and Get methods in your tutorial class are probably being used to implement these features automatically, or at least something similar. The following code would provide that functionality for properties such as the one you posted:

    private Dictionary<string, object> Properties = new Dictionary<string, object>();

    public T Get<T>([CallerMemberName] string propertyName = null)
    {
        if (!Properties.ContainsKey(propertyName))
            Properties[propertyName] = default(T);
        return (T)Properties[propertyName];
    }

    public void Set<T>(T value, [CallerMemberName] string propertyName = null)
    {
        Properties[propertyName] = value;
        RaisePropertyChanged(propertyName);
    }

score 2 · Answer 2 · answered Oct 20 '15 at 12:00

Short answer: No it is not doing the same thing.

The tutorial class depicts that there should be two additional methods like this:

 private void Set(ObservableCollection<string> value)
 {
       //  do something
 }

 private T Get<T>()
 {
       //  do something
 }

The following example is the auto property version of your attempted guess:

public ObservableCollection<string> Directories
{
      get; set;
}

Maybe that is what the tutorial is trying to show?

c# class written in simple terms for wpf mvvm

2 Answers2

Linked