Removing Strings in INotifyPropertyChanged and OData Expands

Ok, so this is a rather random post but I wanted to jot down a couple of scenarios where I often see string literals in code.

Scenario 1: String Literals in INotifyPropertyChanged Implementation

The first is the default implementation of INotifyPropertyChanged. If you’ve done data binding (for example with WPF or Silverlight) you’ll be familiar with this interface – when a source property value changes if you raise the PropertyChanged event the UI gets an opportunity to refresh. The standard implementation looks a bit like this:

public class MainPageViewModel: INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;
    private string _Title;
    public string Title
    {
        get { return _Title; }
        set
        {
            if (Title == value) return;
            _Title = value;
            RaisePropertyChanged("Title");
        }
    }
    private void RaisePropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

I always cringe when I see this because the name of the property, ie “Title” is passed into the RaisePropertyChanged method. This wouldn’t be so bad except this code block gets repeated over and over and over again – for pretty much any property you end up data binding to. Having string literals littered through your code is BAD as it makes your code incredibly brittle and susceptible to errors (for example you change the property name, without changing the string literal). A while ago I adopted the following version of the RaisePropertyChanged method which accepts an Expression and extracts the property name:

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