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.
Related
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 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 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.
I've got a custom WPF control with a DependencyProperty MyString
I'm using the control within an ItemsControl on my View and want to fish a value out from the ViewModel.
As the DataContext of the control becomes each Item in the ItemsSource of the ItemsControl I thought I'd just be able to use FindAncestor but it dosnt seem to work ... can anyone see where I'm going wrong please?
Heres the XAML on the View ...
<Grid>
<ItemsControl ItemsSource="{Binding MyItems}" >
<ItemsControl.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal" Name="myStack">
<ImportExceptions:ControlStrip MyString="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type ItemsControl}}, Path=DataContext.MyStringOnViewModel}" />
</StackPanel>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</Grid>
and heres the code behind my custom control where I've set up my dependency property ...
public partial class ControlStrip
{
public ControlStrip()
{
InitializeComponent();
}
public string MyString
{
get
{
return GetValue(MyStringProperty).ToString();
}
set
{
SetValue(MyStringProperty, value);
}
}
public static readonly DependencyProperty MyStringProperty =
DependencyProperty.RegisterAttached("MyString", typeof (string), typeof (ControlStrip));
}
The DataContext of the control doesn't change - the DataContext for the ImportExceptions:ControlStrip will be (unless explicitly specified) the next DataContext available as its goes 'up' the visual tree...
I infer from your code that you have set the DataContext of the View to a ViewModel with properties 'MyItems' and 'MyStringOnViewModel' - you should be able to simply bind the MyString property directly to the ViewModel, like
<ImportExceptions:ControlStrip MyString="{Binding Path=MyStringOnViewModel}" />
Your code looks fine. Probably you have made an error in the DataContext reference. In all likeliness the DataContext of the the ItemsControl already is MyStringOnViewModel. So, omit the .MystringOnViewModel after the DataContext in the Path attribute. If not can you give some more code, ore post a simplification of it that mimicks how the DataCon,text(s) is/are set?
I have a XAML code that should load my UserControl inside the TabControl.
If I put this XAML code:
<DataTemplate x:Key="WorkspacesTemplate">
<TabControl
IsSynchronizedWithCurrentItem="True"
ItemsSource="{Binding Path=Gui}"
ItemTemplate="{StaticResource ClosableTabItemTemplate}"
Margin="4"
/>
</DataTemplate>
I have absolutly nothing appear in the windows (Gui property is inside the ViewModel class and return a UserControl).
But if I put his XAML code instead of the previous one:
<DataTemplate x:Key="WorkspacesTemplate">
<TabControl
IsSynchronizedWithCurrentItem="True"
ItemsSource="{Binding}"
ItemTemplate="{StaticResource ClosableTabItemTemplate}"
Margin="4"
/>
</DataTemplate>
I have the ViewModel Object loading:
(source: clip2net.com)
Here is a piece of code of the TextBoxInputViewModel that has the property Gui that should be binded to be able to get the Visual (usercontrol):
private UserControl gui;
public UserControl Gui
{
get
{
if (this.gui == null)
{
this.gui = new SimpleTextBoxInputControl();//Xaml User Control
this.gui.DataContext = this;//Bind the Visual and ViewModel
}
return this.gui;
}
}
Any idea how that I can get the UserControl instead of this object reference text?
The problem is that ItemSource is a collection, where as you're binding it to a property that is just one value. The error in the Output window that you're seeing is likely related to this.
Instead of returning a UserControl directly from your View Model, it would be better to return another View Model that represents the contents of the tab, and use templates to display that content. If you need it to be more dynamic than choosing the template based on the Type of the View Model, look into setting TabControl.ContentTemplateSelector. This needs to be set to a class that derives from DataTemplateSelector. You can use this class to decide which template to load based on the object bound to that tab.
you should create a template for your viewmodel in your app.xaml file like this
<DataTemplate DataType="{x:Type simpleModel:TextBoxInputViewModel}">
<myView:TextBoxInputControl />
</DataTemplate>
where simpleModel is the namespace of TextBoxInputViewModel, and TextBoxInputControl is the user control you want to show and myView is the namespace of that user control.