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using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Diagnostics;
using System.Reflection;
namespace CBR.Core.Helpers
{
/// <summary>
/// Implements the INotifyPropertyChanged interface and exposes a RaisePropertyChanged method for derived
/// classes to raise the PropertyChange event. The event arguments created by this class are cached to prevent
/// managed heap fragmentation.
/// </summary>
[Serializable]
public abstract class BindableObject : INotifyPropertyChanged
{
#region Data
private static readonly Dictionary<string, PropertyChangedEventArgs> eventArgCache;
private const string ERROR_MSG = "{0} is not a public property of {1}";
#endregion // Data
#region Constructors
static BindableObject()
{
eventArgCache = new Dictionary<string, PropertyChangedEventArgs>();
}
protected BindableObject()
{
}
#endregion // Constructors
#region Public Members
/// <summary>
/// Raised when a public property of this object is set.
/// </summary>
[field:NonSerialized]
public event PropertyChangedEventHandler PropertyChanged;
/// <summary>
/// Returns an instance of PropertyChangedEventArgs for
/// the specified property name.
/// </summary>
/// <param name="propertyName">
/// The name of the property to create event args for.
/// </param>
public static PropertyChangedEventArgs GetPropertyChangedEventArgs(string propertyName)
{
if (String.IsNullOrEmpty(propertyName))
throw new ArgumentException( "propertyName cannot be null or empty.");
PropertyChangedEventArgs args;
// Get the event args from the cache, creating them
// and adding to the cache if necessary.
lock (typeof(BindableObject))
{
bool isCached = eventArgCache.ContainsKey(propertyName);
if (!isCached)
{
eventArgCache.Add( propertyName, new PropertyChangedEventArgs(propertyName));
}
args = eventArgCache[propertyName];
}
return args;
}
#endregion // Public Members
#region Protected Members
/// <summary>
/// Derived classes can override this method to
/// execute logic after a property is set. The
/// base implementation does nothing.
/// </summary>
/// <param name="propertyName">
/// The property which was changed.
/// </param>
protected virtual void AfterPropertyChanged(string propertyName)
{
}
/// <summary>
/// Attempts to raise the PropertyChanged event, and
/// invokes the virtual AfterPropertyChanged method,
/// regardless of whether the event was raised or not.
/// </summary>
/// <param name="propertyName">
/// The property which was changed.
/// </param>
protected void RaisePropertyChanged(string propertyName)
{
this.VerifyProperty(propertyName);
PropertyChangedEventHandler handler = this.PropertyChanged;
if (handler != null)
{
// Get the cached event args.
PropertyChangedEventArgs args = GetPropertyChangedEventArgs(propertyName);
// Raise the PropertyChanged event.
handler(this, args);
}
this.AfterPropertyChanged(propertyName);
}
#endregion // Protected Members
#region Private Helpers
[Conditional("DEBUG")]
private void VerifyProperty(string propertyName)
{
Type type = this.GetType();
// Look for a public property with the specified name.
PropertyInfo propInfo = type.GetProperty(propertyName);
if (propInfo == null)
{
// The property could not be found,
// so alert the developer of the problem.
string msg = string.Format( ERROR_MSG, propertyName, type.FullName);
Debug.Fail(msg);
}
}
#endregion // Private Helpers
}
}
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WPF and MVVM fan, I practice C # in all its forms from the beginning of the NET Framework without mentioning C ++ / MFC and other software packages such as databases, ASP, WCF, Web & Windows services, Application, and now Core and UWP.
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