how to disable all or some properties PropertyChanged event in WPF? - wpf

Question

How to disable all the properties or some of the properties PropertyChanged event for some time when we are using INotifypropertyChanged?

Answer 1

In order for INotifyPropertyChanged to work, you need to raise the PropertyChanged event. Therefore, to make it not work, you just don't raise that event.
Here's a small example class:
public class NPCExample : INotifyPropertyChanged
{
public NPCExample()
{
}
private string mSomeProperty = "Set Property";
public string SomeProperty
{
get { return mSomeProperty; }
set
{
mSomeProperty = value;
if (mUseNotifyPropertyChanged)
NotifyPropertyChanged("SomeProperty");
}
}
private Boolean mUseNotifyPropertyChanged = true;
public Boolean UseNotifyPropertyChanged
{
get { return mUseNotifyPropertyChanged; }
set
{
mUseNotifyPropertyChanged = value;
NotifyPropertyChanged("UseNotifyPropertyChanged");
}
}
#region INotifyPropertyChanged Members
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
#endregion
}
In this class, each property calls the common "NotifyPropertyChanged" method for raising the PropertyChanged event. There is an additional variable defined (here, I used a public Property so I could bind it to a checkbox) that tells whether or not to raise the event, as used in the SomeProperty event.
Here's a small, quick-n-dirty program to show this in action:
XAML
<Window x:Class="MyNamespace.SelectiveNotifyPropertyChanged"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="SelectiveNotifyPropertyChanged" Height="300" Width="300">
<StackPanel>
<TextBlock Text="{Binding SomeProperty}" />
<CheckBox x:Name="chkINPCEnabled"
Content="Enable INotifyPropertyChanged"
IsChecked="{Binding UseNotifyPropertyChanged}"></CheckBox>
<StackPanel Orientation="Horizontal">
<TextBox x:Name="txtIsProperty"
Text="Set Property" />
<Button x:Name="btnSetProperty"
Content="Set Property" />
</StackPanel>
</StackPanel>
</Window>
Code Behind
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Shapes;
namespace MyNamespace
{
/// <summary>
/// Interaction logic for SelectiveNotifyPropertyChanged.xaml
/// </summary>
public partial class SelectiveNotifyPropertyChanged : Window
{
public SelectiveNotifyPropertyChanged()
{
InitializeComponent();
NPCExample example = new NPCExample();
this.DataContext = example;
btnSetProperty.Click +=
(s, e) => example.SomeProperty = txtIsProperty.Text;
}
}
public class NPCExample : INotifyPropertyChanged
{
public NPCExample()
{
}
private string mSomeProperty = "Set Property";
public string SomeProperty
{
get { return mSomeProperty; }
set
{
mSomeProperty = value;
if (mUseNotifyPropertyChanged)
NotifyPropertyChanged("SomeProperty");
}
}
private Boolean mUseNotifyPropertyChanged = true;
public Boolean UseNotifyPropertyChanged
{
get { return mUseNotifyPropertyChanged; }
set
{
mUseNotifyPropertyChanged = value;
NotifyPropertyChanged("UseNotifyPropertyChanged");
}
}
#region INotifyPropertyChanged Members
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
#endregion
}
}

Answer 2

If you are referring to a binding, you can set the UpdateSourceTrigger to Explicit, which means any changes won't get saved until you explicitly tell it to update
<TextBox Text="{Binding SomeValue, UpdateSourceTrigger=Explicit}" />

Answer 3

Based on your comment to Rachel it sounds like you might want to set the private property backing member sometimes. Could you expose a public method in your underlying class that would set the private member but not call NotifyPropertyChaged?
Public Class SomeClass
... define property SomeProp and m_SomeProp
Public Sub SetSomeProp(val as string)
m_SomePreop=val
End Sub
End Class