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POWhy would INotifyPropertyChanged only fire when at least TWO characters are changed?
 

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  1. POWhy would INotifyPropertyChanged only fire when at least TWO characters are changed?
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    <p>I finally got a Silverlight MVVM example to work so that when I change the values of first name and last name text boxes, the full names change automatically.</p> <p>However, and strangely, my model which inherits from <strong>INotifyPropertyChanged is only notified if I change</strong> <strong><em>at least 2 characters</em></strong> of either the first or last name. </p> <ul> <li>if I change "Smith" to "Smith1", then <strong>no event is fired</strong></li> <li>if I change "Smith" to "Smith12" then the event is fired, as expected</li> </ul> <p>Has anyone run in to this before in Silverlight/XAML/INotifyPropertyChanged? What could it be? <strong>Is there a setting somewhere that indicates how much of a textbox needs to change before it notifies itself as "changed"?</strong></p> <p>Here are the main parts of the code I'm using:</p> <p><strong>Customer.cs:</strong></p> <pre><code>using System; using System.Collections.Generic; using System.ComponentModel; namespace TestMvvm345.Model { public class Customer : INotifyPropertyChanged { public int ID { get; set; } public int NumberOfContracts { get; set; } private string firstName; private string lastName; public string FirstName { get { return firstName; } set { firstName = value; RaisePropertyChanged("FirstName"); RaisePropertyChanged("FullName"); } } public string LastName { get { return lastName; } set { lastName = value; RaisePropertyChanged("LastName"); RaisePropertyChanged("FullName"); } } public string FullName { get { return firstName + " " + lastName; } } #region INotify public event PropertyChangedEventHandler PropertyChanged; private void RaisePropertyChanged(string property) { if (PropertyChanged != null) { PropertyChanged(this, new PropertyChangedEventArgs(property)); } } #endregion } } </code></pre> <p><strong>CustomerHeaderView.xaml:</strong></p> <pre><code>&lt;UserControl x:Class="TestMvvm345.Views.CustomerHeaderView" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Width="400" Height="300"&gt; &lt;Grid x:Name="LayoutRoot" Background="White"&gt; &lt;StackPanel HorizontalAlignment="Left"&gt; &lt;ItemsControl ItemsSource="{Binding}"&gt; &lt;ItemsControl.ItemTemplate&gt; &lt;DataTemplate&gt; &lt;StackPanel Orientation="Horizontal"&gt; &lt;TextBox x:Name="FirstName" Text="{Binding Path=FirstName, Mode=TwoWay}" Width="150" Margin="3 5 3 5"/&gt; &lt;TextBox x:Name="LastName" Text="{Binding Path=LastName, Mode=TwoWay}" Width="150" Margin="0 5 3 5"/&gt; &lt;TextBlock x:Name="FullName" Text="{Binding Path=FullName, Mode=TwoWay}" Margin="0 5 3 5"/&gt; &lt;/StackPanel&gt; &lt;/DataTemplate&gt; &lt;/ItemsControl.ItemTemplate&gt; &lt;/ItemsControl&gt; &lt;/StackPanel&gt; &lt;/Grid&gt; &lt;/UserControl&gt; </code></pre> <p><strong>CustomerViewModel.cs:</strong></p> <pre><code>using System.ComponentModel; using System.Collections.ObjectModel; using TestMvvm345.Model; namespace TestMvvm345 { public class CustomerViewModel { public ObservableCollection&lt;Customer&gt; Customers { get; set; } public void LoadCustomers() { ObservableCollection&lt;Customer&gt; customers = new ObservableCollection&lt;Customer&gt;(); //this is where you would actually call your service customers.Add(new Customer { FirstName = "Jim", LastName = "Smith", NumberOfContracts = 23 }); customers.Add(new Customer { FirstName = "Jane", LastName = "Smith", NumberOfContracts = 22 }); customers.Add(new Customer { FirstName = "John", LastName = "Tester", NumberOfContracts = 33 }); customers.Add(new Customer { FirstName = "Robert", LastName = "Smith", NumberOfContracts = 2 }); customers.Add(new Customer { FirstName = "Hank", LastName = "Jobs", NumberOfContracts = 5 }); Customers = customers; } } } </code></pre> <p><strong>MainPage.xaml.cs:</strong></p> <pre><code>void MainPage_Loaded(object sender, RoutedEventArgs e) { CustomerViewModel customerViewModel = new CustomerViewModel(); customerViewModel.LoadCustomers(); CustomerHeaderView.DataContext = customerViewModel.Customers; } </code></pre> <h1>UPDATE:</h1> <p>I remade this project in WPF and it works fine. Perhaps it's a Silverlight 3 issue.</p>
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    1. USEdward Tanguay
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      1. POWhy would INotifyPropertyChanged only fire when at least TWO characters are changed?
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      1. USEdward Tanguay
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    1. CONot sure what your issue is. By the way as there's no setter for FullName Mode=TwoWay won't work. In case you didn't realise.
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      1. POWhy would INotifyPropertyChanged only fire when at least TWO characters are changed?
      1. USJonathan Parker
    2. COright, FullName needs only be Oneway, but it works well in that when I change "Smith" to "Smith12" and tab off the textbox, the fullname changes. But when I change "Smith" to "Smith1" nothing changes. The issue is: why does the textbox register as changed only when at least TWO chars are changed?
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      1. POWhy would INotifyPropertyChanged only fire when at least TWO characters are changed?
      1. USEdward Tanguay
 

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