I've searched here a number of times and found a bunch of examples, but can't seem to get anything to work.
I've got a solution set up where a ViewModel refers to a MainViewModel class through a locator. The main view model class has:
public NotifyLog Log
{
get { return LogMgr.Instance.Log; }
}
In it. This allows me to specify:
<TextBox IsEnabled="True" Text="{Binding Log.Text, Mode=OneWay}" />
The NotifyLog is defined as:
public class NotifyLog : INotifyPropertyChanged
{
public NotifyLog()
{
_Log = new StringBuilder();
}
private void OnPropertyChanged(string property)
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(property));
}
public event PropertyChangedEventHandler PropertyChanged;
private StringBuilder _Log;
public void Append(String Value)
{
_Log.Append(Value);
OnPropertyChanged("Text");
}
public string Text
{
get { return _Log.ToString(); }
}
public override string ToString()
{
return this.Text;
}
}
For the initial start of the application, the text box is populated but, the OnPropertyChanged handler is never automatically populated by the binding so no changes are detected. I'm doing something wrong, I just don't know what...
Thanks for your time,
BlD
if you want to update the log when typing in the text box you need to change the binding mode to TwoWay. also the event is triggered when you exit from the text box, not on each char typed.
if you want to update the text box when the log is changed you need to add a setter to the Text property and raise the NotifyPropertyChanged event (in the setter).
also check the output of the program for some binding errors.
To the line:
<TextBox IsEnabled="True" Text="{Binding Log.Text, Mode=OneWay}" />
Try adding the "UpdatedSourceTrigger" like so:
<TextBox IsEnabled="True" Text="{Binding Log.Text, Mode=OneWay, UpdateSourceTrigger=PropertyChanged}" />
Related
In my app I have a user control with the following XAML segment
<StackPanel x:Name="stackPanel" Style="{StaticResource sPanel1}" >
<ToggleButton Style="{StaticResource tButton}">
<TextBlock Text="{Binding Note, Mode=TwoWay}" Style="{StaticResource textBlockStyle}"/>
</ToggleButton>
</StackPanel>
that 'Note' bound in the TextBlock is defined in my model as so:
private string m_Note;
public string Note
{
get { return m_Note; }
set
{
m_Note = value;
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs("m_Note"));
}
}
The 'Note' property updates when an event handler from my user control code-behind fires the event:
public void cBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
cm.Note = cBox.SelectedItem.ToString();
}
But every time I select an item from the ComboBox the UI does not update. I know that the binding is correct because when I initialize 'Note' in the model's constructor it does show it's value in the UI, and I know that 'Note' gets the cBox.SelectedItem value because I've walked through the code. What am I missing?
The binding path and mode in the View is correct. That is why you get the value on initialize. Your bound property however is not raising the correct Property Name on property changed. The UI is listening for Note but you are raising m_Note.
You need to update to
private string m_Note;
public string Note
{
get { return m_Note; }
set
{
m_Note = value;
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs("Note"));
}
}
I am very new to the concept of data binding and I don't think I understood it completely. I have a class named Project with a LinkedList of type ToDo as one of its properties. When I navigate to one instance of Project, I will display the LinkedList of type ToDo in a ListView. I have created functions that allow me to change the sequences of the nodes in the LinkedList (move up, move down) and to remove the selected node (delete). I want the ListView to refresh whenever there is a change in the LinkedList, (move up, move down or delete). However, I cannot achieve that. Here is my code: (not all parts are included)
XAML of the page:
<ListView x:Name="myListView" ItemsSource="{Binding Source={StaticResource ToDos}, Mode=TwoWay}">
<ListView.ItemTemplate>
<DataTemplate>
<StackPanel>
<CheckBox x:Name="myCheckBox"
Content="{Binding ToDoTitle, Mode=TwoWay}"
IsChecked="{Binding IsCompleted, Mode=TwoWay}">
</StackPanel>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
C# for DataModel:
public class ToDo : INotifyPropertyChanged
{
private string toDoTitle;
private bool isCompleted;
public event PropertyChangedEventHandler PropertyChanged = delegate { };
public string ToDoTitle { get { return this.toDoTitle; } set { this.toDoTitle = value; this.OnPropertyChanged(); } }
public bool IsCompleted { get { return this.isCompleted; } set { this.isCompleted = value; this.OnPropertyChanged(); } }
public void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
// Raise the PropertyChanged event, passing the name of the property whose value has changed.
this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
public class Projects : INotifyPropertyChanged
{
private LinkedList<ToDo> toDos;
public event PropertyChangedEventHandler PropertyChanged = delegate { };
public LinkedList<ToDo> ToDos { get { return this.toDos; } set { this.toDos = value; this.OnCollectionChanged(); } }
public Projects()
{
ToDos = new LinkedList<ToDo>();
}
public void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
// Raise the PropertyChanged event, passing the name of the property whose value has changed.
this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
Thank you.
First I would advise you to read about MVVM, and try to follow some basic tutorials like this one.
You can use MVVM Light to avoid managing the INotifyPropertyChanged by yourself at first (but it's really good to know how MVVM light work under the hood).
To come back to your problem, your current code notifies only if you set the full ToDos list. If you want to be aware of any change in a list (seing when an item is add/remove/update), you are probably looking for an ObservableCollection, not a LinkedList.
Hope it helps.
Is it usable or this doesn't work: to change the Text Box.Text and the property behind to change can a binding of this type be made(i know that this can be made with an event from Text Box, i am looking for some kind of binding that can be made) ?
Should i just use Text Box.Text in my cod?
<TextBox Text="{Binding Path=NumeClient, Mode=TwoWay}" Height="23" HorizontalAlignment="Left" Margin="117,21,0,0" Name="textBox1" VerticalAlignment="Top" Width="249" />
public string NumeClient { get; set; }
If I understand the question correctly, you're asking how to setup a two way binding to the Text property of a TextBox?
<TextBox Text="{Binding Path=YourProperty, Mode=TwoWay}" />
This Makes both your property changes the TextBox and the TextBox changes the property (from MSDN)
Add in your class contructor DataContext = this;
public class Person : INotifyPropertyChanged
{
private string name;
// Declare the event
public event PropertyChangedEventHandler PropertyChanged;
public string PersonName
{
get { return name; }
set
{
name = value;
// Call OnPropertyChanged whenever the property is updated
OnPropertyChanged("PersonName");
}
}
// Create the OnPropertyChanged method to raise the event
protected void OnPropertyChanged(string name)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(name));
}
}
}
XAML :
<TextBox Text="{Binding Path=PersonName, Mode=TwoWay}" />
Hope it helps
I want to read value entered in the NumericUpDown control. How do i read it?
XAML Layout is follows
<StackPanel Style="{StaticResource StackPanelStyle_LableValue}">
<TextBlock Style="{StaticResource TextBlockStyle}"
Text="{Binding Path=ViewItem.Addition, Source={StaticResource LocalizedStrings }}" />
<inputToolkit:NumericUpDown Style="{StaticResource NumericUpdownStyle_Addition}"
Value="{Binding Items.RightSpecGlass.Addition, Mode=TwoWay}"
TabIndex="8" />
</StackPanel>
You can use
numericUpDown.Value; // To get decimal value of control
or
numericUpDown.Text; // To get value as string of control
Well, Since you have bind your view context, I think there is no reason to avoid get NumericUpDown's value except :
1- Maybe you forgot to initialize those classes or properties Items and/or RightSpecGlass
2- Your class doesn't implement INotifyPropertyChanged to raise when any control's value change in view. Addition property has to raise property change event in its setter.
public event PropertyChangedEventHandler PropertyChanged;
public virtual void RaisePropertyChanged(string propertyName)
{
var handler = PropertyChanged;
if (handler != null)
handler(this, new PropertyChangedEventArgs(propertyName));
}
private int _addition;
public Int32 Addition
{
get { return _addition; }
set
{
_addition= value;
RaisePropertyChanged("Addition");
}
}
hope this help.
I'm trying to update a property using a PropertyChangedEventHandler, but I think my conceptual understanding of how this works might be a bit flawed. As I'm new to WPF and silver-light.
So, let me explain, I have a property that is set to 0, but after some time a thread changes the value from 0 to 9 internally, but despite the change in value, this property never gets updated in the actual view and I don't know why! Even after I implement a PropertyChangedEventHandler there is no change, but if I log the property it shows that the value is in fact 9
So here is the snippet of code that implements PropertyChangedEventHandler:
public class CustomColumn : IColumnViewable, INotifyPropertyChanged
{
...
public event PropertyChangedEventHandler PropertyChanged = delegate { };
public void OnPropertyChanged(string propertyName)
{
Foo.log.Error(": start on property change");
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
Foo.log.Error(": end on property change");
}
public static string _total;
public string total { get { return _total; } set { _total = value; OnPropertyChanged("total"); Foo.log.Error(": property change"); } }
...
}
Here is part of my xaml:
<DataTemplate x:Key="ColumnView">
<UserControl HorizontalAlignment="Stretch">
<StackPanel HorizontalAlignment="Stretch">
...
<RichTextBox Margin="5,2,5,2">
<Paragraph>
<Run Text="{Binding Path=total, Mode=OneWay}" FontWeight="Bold" FontSize="30" />
<Run Text=" total clicks" FontWeight="Bold" />
</Paragraph>
</RichTextBox>
...
<ContentControl VerticalAlignment="Stretch" Content="{Binding Path=timeline}" ContentTemplate="{Binding Path=timelineView.ContentTemplate}" />
</StackPanel>
</UserControl>
</DataTemplate>
And I do this on initialize:
CustomColumn content = new CustomColumn();
content.total = "0";
And then I pass the object to a thread which at some point does this:
content.total = "9";
Foo.log.Error("value is "+content.total);
And the property never updates and I don't know why - any help is greatly appreciated
If I understand the details of your question, you are updating a UI bound value on a background thread. You need to make that happen on the UI thread or the change will not be visible. In one of our WPF apps random updates were disappearing until we realised this.
We do a lot of multi-threading in our Silverlight (and WPF) apps so to avoid this problem, we implemented our notify helper in a base class like the one below (other stuff trimmed out). It dispatches all notify messages on the main UI thread. Give it a try:
public class ViewModelBase : INotifyPropertyChanged
{
protected delegate void OnUiThreadDelegate();
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void SendPropertyChanged(string propertyName)
{
if (this.PropertyChanged != null)
{
// Ensure property change is on the UI thread
this.OnUiThread(() => this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName)));
}
}
protected void OnUiThread(OnUiThreadDelegate onUiThreadDelegate)
{
// Are we on the Dispatcher thread ?
if (Deployment.Current.Dispatcher.CheckAccess())
{
onUiThreadDelegate();
}
else
{
// We are not on the UI Dispatcher thread so invoke the call on it.
Deployment.Current.Dispatcher.BeginInvoke(onUiThreadDelegate);
}
}
}
Your code does not show where you make the object the DataContext of your controls, which is necessary for your bindings which do not specify another source and hence bind to the DataContext.
CustomColumn content = new CustomColumn();
content.total = "0";
Do you have any line after this where this object is passed to your view?