I can't seem to pick my way through Telerik's terrible documentation for binding through an MVVM situation. We've got the standard view, and view model. The viewmodel exposes a property, 'Body' that is supposed to represent what the user is typing. Here are the relevant lines of xaml:
<telerik:DocxDataProvider
x:Name="DocxProvider"
RichTextBox="{Binding ElementName=editor}"
Docx="{Binding Body, Mode=TwoWay,
UpdateSourceTrigger=LostFocus}" />
<telerik:RadRichTextBox
Grid.Row="1"
x:Name="editor"
Margin="0"
AllowDrop="True"
ShowComments="False"
MinWidth="800"
MinHeight="300"
MaxWidth="1024"
MaxHeight="1200"
HorizontalAlignment="Left"
HorizontalContentAlignment="Left"
Width="790"
Padding="20,20,0,20"
TabIndex="10"
Cursor="IBeam"
IsSpellCheckingEnabled="True" >
</telerik:RadRichTextBox>
But when I set a break point on Body, it never gets hit. What property do I need to bind to so that my view model actually gets the content of the text box?
Have you tried binding to Rtf property of telerik:RadRichTextBox; another thing can be the ordering of your elements, can you try declaring <telerik:RadRichTextBox before <telerik:DocxDataProvider
Also have a look at this thread on telerik forum -
http://www.telerik.com/community/forums/wpf/richtextbox/binding-document.aspx
Did you remember to set the datacontext in the constructor of the xaml.cs file:
public View(ViewModel viewModel)
{
InitializeComponent();
DataContext = viewModel;
}
This is how you hook up the viewmodel to the view.
Related
I have a UserControl positioned inside of the MainWindow. The UserControl runs a query and populates certain TextBlocks within it. I also want to populate TextBlock in the MainWindow from the same returned data.
How do I bind the MainWindow data to the UserControl? I have tried this:
<MainWindow DataContext="{Binding Path=DataContext, ElementName=UserControlName}">
Any help would be appreciated. Thanks!
Here is a simple working example.
The UserControl XAML contains just a two-way bound text box. The relative source stuff is more verbose than you need, you could have a data context set above that, but it's just to make it clear where the property is coming from:
<TextBox x:Name="ucTextBox"
Text="{Binding Path=UcText,
RelativeSource={RelativeSource AncestorType={x:Type local:UserControl1}},
Mode=TwoWay,
UpdateSourceTrigger=PropertyChanged}" />
User Control code behind declares either a dependency property or, as shown here, a regular property implementing INotifyPropertyChanged:
private string _ucText;
public string UcText
{
get { return _ucText; }
set
{
_ucText = value;
OnPropertyChanged("UcText");
}
}
The MainWindow XAML then sets it's own text block to the text property from the textbox in the user control, like so:
<StackPanel Orientation="Vertical">
<TextBlock Text="{Binding Path=UcText, ElementName=uc1}"/>
<local:UserControl1 x:Name="uc1" />
</StackPanel>
Nothing extra is required in the MainWindow codebehind.
What this results in is a text box (in the user control) which - as you type inside it - updates the text block on the main window.
I'm totally lost with dependancy objects and binding. I often get things working without understanding why and how, this question is about knowing what should be happening.
I have a tiny user control with the following XAML
<Grid>
<Image Source="{Binding Icon}"></Image>
<TextBlock Text="{Binding Title}"></TextBlock>
</Grid>
My code behind has the following
public static readonly DependencyProperty IconProperty =
DependencyProperty.Register("Icon", typeof(Image), typeof(MenuItem));
public Image Icon
{
get { return (Image)GetValue(IconProperty); }
set { SetValue(IconProperty, value); }
}
public static readonly DependencyProperty TitleProperty =
DependencyProperty.Register("Title", typeof(String), typeof(MenuItem));
public string Title
{
get { return (string)GetValue(IconProperty); }
set { SetValue(IconProperty, value); }
}
My MainWindow is empty, other than a reference to this control and to the ResourceDictionary. In the MainWindow code behind, I set the DataContext in the constructor.
<Window x:Class="AppUi.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:loc="clr-namespace:AppUi.Control"
Title="">
//set up to Resource Dictionary - all binding and styling works fine :)
<loc:MenuItem Icon="{Binding MailIcon}" Title="{Binding MailTitle}"></loc:MenuItem>
In the ModelView for the MainWindow, I have the following 2 properties
private Image_mailIcon;
public Image MailIcon{
//inotifyproperty implementation
}
private string _mailTitle;
public string MailTitle{
//inotifyproperty implementation
}
My question is, in the UserControl, how do I do the binding? Since it's a user control within a MainWindow, and the MainWindow already has a datacontext, I think the UserControl will inherit the DataContext from the parent (From what I have read).
So, in my UserControl XAML, should I be binding to the MainWindow's Code Behind properties OR to the ViewModel properties?
In other words, should my UserControl be
<Grid>
<Image Source="{Binding MailIcon}"></Image>
<TextBlock Text="{Binding MailTitle}"></TextBlock>
</Grid>
OR
<Grid>
<Image Source="{Binding Icon}"></Image>
<TextBlock Text="{Binding Title}"></TextBlock>
</Grid>
Or, because I'm using a DataContext and the UserControl inherits, do I even need the Dependancy Properties at all?
You normally don't want to overwrite DataContext passed through visual tree so you can use either ElementName or RelativeSource binding inside UserControl to change binding context. The easiest way to achive this is give UserControl some name and use it ElementName binding
<UserControl ... x:Name="myUserControl">
<!-- ... -->
<Grid>
<Image Source="{Binding Icon, ElementName=myUserControl}"/>
<TextBlock Text="{Binding Title, ElementName=myUserControl}"/>
</Grid>
<!-- ... -->
</UserControl>
This way binding is DataContext independent. You can also create UserControl with assumption it will always work with only specific type of DataContext and then you just use Path from that view model type but then DataContext of that UserControl must always be of the view model it's designed for (mostly inherited through visual tree)
<UserControl ...>
<!-- ... -->
<Grid>
<Image Source="{Binding MailIcon}"/>
<TextBlock Text="{Binding MailTitle}"/>
</Grid>
<!-- ... -->
</UserControl>
I would also change type of Icon property from Image to ImageSource for example. You already have Image control inside your UserControl and you just want to bind its Source
in the UserControl, how do I do the binding? ... the UserControl will inherit the DataContext from the parent
That is correct, the UserControl will inherit the DataContext from the parent Window. Therefore you can data bind from the UserControl directly to the parent Window.DataContext. Please note that you would bind to whatever object has been set as the DataContext, regardless of whether that was the code behind or a separate view model class.
However, you don't have to data bind to the parent's DataContext object in this situation... you have other options. You could data bind to your own UserControl DependencyPropertys using a RelativeSource Binding like this:
<TextBlock Text="{Binding Title, RelativeSource={RelativeSource
AncestorType={x:Type YourPrefix:YourUserControl}}}" />
You could also name your UserControl and reference its properties like this:
<TextBlock Text="{Binding Title, ElementName=YourUserControlName}" />
While this example seems to be more concise, don't overlook the first example, as RelativeSource is a useful and powerful friend to have.
should I be binding to the MainWindow's Code Behind properties OR to the ViewModel properties?
That's your choice... what do you want or need to data bind to? you just need to know that a direct data binding will use the auto set DataContext value, so if you don't want to use that, then you can just specify a different data source for the Binding as shown above.
Finally, regarding the need to use DependencyPropertys... you only need to declare them if you are developing a UserControl that needs to provide data binding abilities.
I'm building a graphical designer, based upon an article by Sukram in CodeProject. I'm now trying to extend it so that each item on the canvas binds to a different ViewModel object - i.e. I'm setting the DataContext for each item.
Every item on the designer is actually a ContentControl, into which is placed a different template (based upon which toolbox item was dragged onto the canvas). So I have a template containing a TextBox, and I have a ViewModel object containing a Name property, and I bind the Text property of the TextBox to the Name property of the ViewModel, and ... nothing. I've checked the visual tree with Snoop, and it confirms that the DataContext of the TextBox is the ViewModel object. Yet the TextBox remains empty. And if I modify the (empty) Text in the TextBox, the Name property in the ViewModel does not change. So it looks like the binding is not being applied (or has been removed somehow).
I've found a few posts which talk about the ContentControl messing around with the DataContext and Content properties, but I'm not sure how applicable they all are. The code sets the ContentControl.Content as follows:
newItem = new ContentControl();
ControlTemplate template = toolbox.GetTemplate();
UIElement element = template.LoadContent() as UIElement;
ViewModelItem viewModel = new ViewModelItem() { Name = "Bob" };
newItem.Content = element;
newItem.DataContext = viewModel;
and the XAML for the template is:
<ControlTemplate>
<Border BorderBrush="Black" BorderThickness="1" Width="100">
<TextBox Text={Binding Name}/>
</Border>
</ControlTemplate>
Snoop shows that the TextBox has a DataContext, and if I Delve that DataContext I can see that it has a Name property whose value is "Bob". So why does the TextBox remain empty? Snoop allows me to change that Name property, but the TextBox remains empty.
What am I doing wrong?
A few more details. I've set the VS2010 Debug DataBinding option for the OutputWindow to Verbose, which seems to show that the binding is all being attempted before I set the DataContext. Is it possible that the change to the DataContext is not being recognised?
I've just found this post DataTemplate.LoadContent does not preserve bindings - apparently DataTemplate.LoadContent does not preserve bindings. So it looks like I have to write my own version of LoadContent().
I've realised that the template has come through a XamlWriter, which apparently strips all bindings. This wouldn't be helping.
I've not been able to fix the DataTemplate.LoadContent(), but I realised that I didn't actually need a DataTemplate, since the XamlWriter / XamlReader was already instantiating the UI element that I was after. I found a fix to make the XamlWriter write all the bindings here, and after that it all works.
Thanks for your help.
Maybe you need to tell the binding in the ControlTemplate to look at the TemplatedParent, as is mentioned in this thread?
<TextBox Text="{Binding Path=Name, RelativeSource={RelativeSource TemplatedParent}}"/>
Either that, or try to use a DataTemplate instead.
I can't test this at the moment, so I might just be guessing here.
I would use a DataTemplate, as bde suggests.
You are trying to put some UI on your own data (ViewModel), and this is what Data-Templates are meant for (ControlTemplate is usually what you use if you want to change how e.g. a Button looks).
Change your code to use ContentControl.ContentTemplate with a DataTemplate:
<DataTemplate>
<Border BorderBrush="Black" BorderThickness="1" Width="100">
<TextBox Text={Binding Name}/>
</Border>
</DataTemplate>
Code-behind:
newItem = new ContentControl();
//NOTE: .GetTemplate() needs to return a DataTemplate, and not a ControlTemplate:
newItem.ContentTemplate = toolbox.GetTemplate();
ViewModelItem viewModel = new ViewModelItem() { Name = "Bob" };
newItem.Content = viewModel;
newItem.DataContext = viewModel;
I have a Tree View, I am using a Text block inside my Tree view Item.I can not able to bind text for text block When I used "Data context" for my Treeview Item. Can any one help me in fixing this Issue.
here is my xaml code..
<TreeViewItem ItemsSource="{Binding}" DataContext="{Binding XYZ}">
<TreeViewItem.Header>
<StackPanel>
<Image Source="abc.png" />
<TextBlock Text="{Binding BindContent}"></TextBlock>
</StackPanel>
</TreeViewItem.Header>
</TreeViewItem>
in My View Model, I am using
private string _content;
public string BindContent
{
get{ return _content;}
set{_content= value;}
}
In my constructor I am setting value for Content...
It is working fine when I used static content (or) when I am not using
Data context for Treeview Item. but for some other reasons i need to use Data Context.
How can I bind Content for Text block When I used Data Context for Tree view Item...
Thanks in Advance.
I think the problem could be that you are not implementing the INotifyPropertyChanged or you are not raising the notify property changed event. By default the text is null, then you set it in your ViewModel's constructor, but if it is not INotifyPropertyChanged then the view will not be notified.
Hope this could helps you to solve the problem...
Two things you can do,
Make sure your viewmodel implements INotifyPropertyChanged as suggested by Raul Otario and you raise the event on property change,
Secondly, you can use relative source in your binding something like, UserControl if your xaml is on usercontrol else Window
<TextBlock Text="{Binding Path=DataContext.BindContent,
RelativeSource={RelativeSource FindAncestor,
AncestorType={x:Type UserControl}}}"/>
Hope it helps...
I have another WPF databinding question... one that I haven't found an answer to anywhere, and this surprises me since it seems like it is very basic.
Essentially, I have a string in code behind that I would like to establish a two-way binding with with a textbox in my GUI. I thought it was a simple matter of creating a DependencyProperty in the code behind, and then tying it to the TextBox via a Source binding. The problem is, I can't get one or both parts right.
Here is my DependencyProperty definition from the code behind:
public static readonly DependencyProperty FilePathProperty = DependencyProperty.Register( "FilePath", typeof(string), typeof(Window1));
public string FilePath
{
get { return (string)GetValue(FilePathProperty); }
set { SetValue( FilePathProperty, value); }
}
And here is my XAML:
<Window
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="ReportingInterface Test Application" Height="300" Width="536">
<Menu DockPanel.Dock="Top">
<MenuItem Name="menu_plugins" Header="File">
<MenuItem Header="Open">
<StackPanel Orientation="Horizontal">
<Label>File location:</Label>
<TextBox Name="text_filepath" Width="100" Text="{Binding Source=FilePath, Path=FilePath, Mode=TwoWay}"></TextBox>
<Button Margin="3" Width="20">...</Button>
</StackPanel>
</MenuItem>
</MenuItem>
</Menu>
The part I know is obviously wrong is the Binding part... I hate to waste people's time here with this question, but I honestly have come up short with every search (but now at least this request will populate subsequent google searches). :)
Thank you!
When you defined a binding in XAML, it binds to whatever is set as the DataContext for the object (or it's parent).
This typically means you'd set the DataContext of the Window to some class, and then the binding will work:
<TextBox Name="text_filepath" Width="100" Text="{Binding Path=FilePath, Mode=TwoWay}" />
You can fix this by adding, in the Window's constructor:
this.DataContext = this;
That will make the binding work against the window itself.
Alternatively, you can setup the binding to bind against a specific source object. If, in this case, you wanted to be able to use something else as the DataContext, but still want to bind to a Dependency Property defined in your Window, you could do:
<TextBox Name="text_filepath" Width="100" Text="{Binding Path=FilePath, RelativeSource={RelativeSource FindAncestor, AncestorType=Window}}"></TextBox>
This works by telling the binding to find the first ancestor of type "Window", and bind it the "FilePath" property on that object.
For what it's worth, I would recommend looking into the M-V-VM pattern (Model, View, ViewModel)- essentially, what you do is have this class that serves as the DataContext for your XAML, and all your fun exposed properties/commands/what have you are exposed as public members of that class (called a ViewModel).
Here's a good overview webcast:
MVVM video
And here's another from MSDN mag:
http://msdn.microsoft.com/en-us/magazine/dd419663.aspx