INotifyPropertyChanged diagnostics

Those of you that use INotifyPropertyChanged may have noticed it's easy to break the code if you choose to refactor/rename as the property name string does not get refactored.

Here is a mechanism to catch this problem at the implementation stage.

[code:c#]

#region Debugging Aides

///
/// Warns the developer if this object does not have
/// a public property with the specified name. This
/// method does not exist in a Release build.
///
[Conditional("DEBUG")]
[DebuggerStepThrough]
public void VerifyPropertyName(string propertyName)
{
// Verify that the property name matches a real,
// public, instance property on this object.
if (TypeDescriptor.GetProperties(this)[propertyName] == null)
{
string msg = "Invalid property name: " + propertyName;

if (this.ThrowOnInvalidPropertyName)
throw new Exception(msg);
else
Debug.Fail(msg);
}
}

///
/// Returns whether an exception is thrown, or if a Debug.Fail() is used
/// when an invalid property name is passed to the VerifyPropertyName method.
/// The default value is false, but subclasses used by unit tests might
/// override this property's getter to return true.
///
protected virtual bool ThrowOnInvalidPropertyName { get; private set; }

#endregion // Debugging Aides

#region INotifyPropertyChanged Members

///
/// Raised when a property on this object has a new value.
///
public event PropertyChangedEventHandler PropertyChanged = (s, e) => { };

///
/// Raises this object's PropertyChanged event.
///
/// The property that has a new value.
protected virtual void OnPropertyChanged(string propertyName)
{
this.VerifyPropertyName(propertyName);
this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}

#endregion // INotifyPropertyChanged Members

[/code]