/// <summary>
/// Set the property with the specified value. If the value is not equal with the field then the field is
/// set, a PropertyChanged event is raised and it returns true.
/// </summary>
/// <typeparam name="T">Type of the property.</typeparam>
/// <param name="field">Reference to the backing field of the property.</param>
/// <param name="value">The new value for the property.</param>
/// <param name="propertyName">The property name. This optional parameter can be skipped
/// because the compiler is able to create it automatically.</param>
/// <returns>True if the value has changed, false if the old and new value were equal.</returns>
protected bool SetProperty <T>(ref T field, T value, [CallerMemberName] string propertyName = null)
{
//compare to the old value
if (object.Equals(field, value))
{
return(false);
}
//get fields old value
var oldValue = field;
//set field to new value
field = value;
//create new arguments
var args = new PropertyChangedEventArgsEx(propertyName, value, oldValue);
//raise event
RaisePropertyChanged(args);
//inform subclasses
OnPropertyChanged(this, args);
//return true since property was changed
return(true);
}
/// <summary>
/// Raises PropertyChanged event.
/// </summary>
/// <param name="sender">Event sender.</param>
/// <param name="args">Event arguments.</param>
protected void RaisePropertyChanged(object sender, PropertyChangedEventArgsEx args)
{
if (sender == null)
{
throw new ArgumentNullException(nameof(sender));
}
if (args == null)
{
throw new ArgumentNullException(nameof(args));
}
//process event in derived classes
if (OnPropertyChanging(sender, args))
{
PropertyChanged?.Invoke(sender, args);
}
}
/// <summary>
/// This method is called when property changed and we aboout to raise PropertyChanged event.
/// </summary>
/// <returns>
/// True if PropertyChanged should be raised otherwise false.
/// </returns>
/// <param name="sender">Event sender.</param>
/// <param name="args">Event arguments.</param>
protected virtual bool OnPropertyChanging(object sender, PropertyChangedEventArgsEx args)
{
return(true);
}
/// <summary>
/// Raises PropertyChanged event.
/// </summary>
/// <param name="args">PropertyChangedEvent aruments.</param>
protected void RaisePropertyChanged(PropertyChangedEventArgsEx args)
{
//Null or empty string propertyName should be allowed http://msdn.microsoft.com/en-us/library/system.componentmodel.inotifypropertychanged.propertychanged.aspx
RaisePropertyChanged(this, args);
}
/// <summary>
/// This method is called once property has changed and processed.
/// </summary>
/// <param name="sender">Event sender.</param>
/// <param name="args">Event arguments.</param>
protected virtual void OnPropertyChanged(object sender, PropertyChangedEventArgsEx args)
{
}