An elegant way to write WPF Models and ViewModels
In WPF, to send notification of value changed of model’s
property to view, you must have to implement
INotifyPropertyChanged interface. Here in following example, ViewModelbase has implementation
of INotifyPropertyChanged so when you inherit from ViewModelbase class to your
models and ViewModels, you no need to re-implement same interface again. This
class has NotifyPropertyChanged ovverloaded methods which allows you
to send notification to view with and without value compare.
public abstract class ViewModelbase : INotifyPropertyChanged
{
protected void NotifyPropertyChanged<T>(Expression<Func<T>> memberExpression)
{
if (memberExpression == null)
{
throw new ArgumentNullException("memberExpression");
}
var body = memberExpression.Body as MemberExpression;
if (body == null)
{
throw new ArgumentException("Lambda must return a property.");
}
if (PropertyChanged != null)
{
var vmExpression = body.Expression as ConstantExpression;
if (vmExpression != null)
{
var lambda = Expression.Lambda(vmExpression);
var vmFunc = lambda.Compile();
var sender = vmFunc.DynamicInvoke();
PropertyChanged(sender, new PropertyChangedEventArgs(body.Member.Name));
}
}
}
protected void NotifyPropertyChanged<T>(Expression<Func<T>> memberExpression, ref T oldValue, ref T newValue)
{
if (EqualityComparer<T>.Default.Equals(oldValue, newValue))
{
return;
}
NotifyPropertyChanged(memberExpression);
}
public event PropertyChangedEventHandler PropertyChanged;
}
Inherit person class from ViewModelbase
public class Person : ViewModelbase
{
private string _name;
public string Name
{
get { return _name; }
set
{
_name = value;
NotifyPropertyChanged(()=>Name);
}
}
private int _age;
public int Age
{
get { return _age; }
set
{
NotifyPropertyChanged(() => Age, ref _age, ref value);
_age = value;
}
}
