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.
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 have a couple specific user controls to Show some Content, e.g. simple like Image, WebControl but also two complex specific custom controls drawing on a canvas.
Now I thought using the DataTemplateSelector to handle the different UserControls. I actully used this http://tech.pro/tutorial/807/wpf-tutorial-how-to-use-a-datatemplateselector as a reference.
I changed the code so the form loads the UserControls dynamically (according to the file extension) in the following collection:
ObservableCollection<string> _pathCollection = new ObservableCollection<string>();
The only difference to the reference is now I want to navigate back and forward to the next control by showing one control only at the time. Which control should I use instead of ListView?
<Grid>
<ListView ScrollViewer.CanContentScroll="False"
ItemsSource="{Binding ElementName=This, Path=PathCollection}"
ItemTemplateSelector="{StaticResource imgStringTemplateSelector}">
</ListView>
</Grid>
How do I need to bind it to the template (equal to ItemTemplateSelector above)? WPF is still very new to me and I am learning.
Use a ContentControl. Bind your current item to the Content-property and the DataTemplateSelector to the ContentTemplateSelector-property.
<ContentControl Content="{Binding Path=CurrentItem, Mode=OneWay}", ContentTemplateSelector="{StaticResource imgStringTemplateSelector}" />
Your CurrentItem should be a DependencyProperty or a INotifyPropertyChanged-property of your DataContext. When you change your CurrentItem, the ContentControl will update the template automatically with help of your TemplateSelector.
For some reason I am unable to bind to ViewModel properties within DataTemplates on some controls. The result of the binding itself is unpredictable, sometimes it work, sometimes it doesn't. For this reason I am thinking of exposing the ViewModel in some other way besides setting it as DataContext.
First thought was to add ViewModel to Resources collection. I am using TabControls for UI, so whenever a view needs to be displayed, it is done through Data templates.
<DataTemplate DataType="{x:Type vm:SomeViewModel}">
<vw:SomeView />
</DataTemplate>
In this situation the view is instantiated automatically, and its DataContext is set to ViewModel set in template. Is there a way I can make this ViewModel available to View's Resources (ex with key=viewModel), so that I can use it like this:
<TextBlock Text="{Binding SomeProperty, Source={StaticResource viewModel}}" />
I have tried adding it in code, in the Loaded event for the View:
this.Loaded += (s, e) =>
{
this.Resources.Add("viewModel", this.DataContext);
};
Above code is executed before the error pops up that says static resource is not found at run-time, so the resource was added to collection.
Any ideas what can I do?
You can define ViewModel as a resource in XAML like that:
<vm:SomeViewModel x:Key="ViewModel"/>
If you want to Bind to DataContext in a DataTemplate you can use the following:
{Binding Path=DataContext, ElementName=uc}
assuming that your window/usercontrol name is x:Name="uc" , or as #stukselbax wrote:
{Binding Path=DataContext, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=[UserControl|Window]}}
New to WPF/MVVM. I have a data object of type "MyData". One of its properties is of type "MySubsetData".
I show a collection of "MyData" objects in a datagrid.
<DataGrid ItemsSource="{Binding Path=MyDataCollection}">
<!-- Each row of the datagrid contains an item of type "MyData" -->
<DataGrid.Columns .../>
<DataGrid.RowDetailsTemplate>
<DataTemplate>
<local:MySubsetDataUserControl/>
</DataTemplate>
</DataGrid.RowDetailsTemplate>
</DataGrid>
The row details should show the content of "MySubsetData". The view of the row details is in a separate user control (here: "MySubsetDataUserControl").
At the moment I don't set a view model for "MySubsetDataUserControl", so it inherits the data context from the parent's datagrid row.
<UserControl>
<!-- Namespace stuff not shown for simplicity -->
<Grid DataContext="{Binding Path=MySubsetData}">
<!-- Show the MySubsetData properties here -->
<!-- e.g. a textbox -->
<TextBox Text="{Binding Path=TextData, UpdateSourceTrigger=PropertyChanged}"/>
</Grid>
</UserControl>
Altough this is working I face several problems with this approach:
All business logic will be in the user control parent's view model, where it simply doesn't belong. Making the view model messier than it need to be. Not to mention that command bindings in the user controls xaml look very ugly as well. It just doesn't feel right.
As more row details could be visible at the same time, I can't bind the properties of "MySubsetData" to an observable property in the view model. I.e. if I change a property in code (e.g. TextData) the change will not be reflected in the view. My workaround is not to alter the property "TextData". Instead I change the content of the textbox Text property, which in turn will update the "TextData" property. And that feels very wrong!
So I would like to use another view model for my user control, but I don't know how to access my data then.
<UserControl.DataContext>
<local:UserControlViewModel/>
</UserControl.DataContext>
How do I access "MySubsetData" now?
Let assume you have a view model like this:
public class ViewModel
{
public IEnumerable<MyData> MyDataCollection{get; private set;}
}
Where
public class MyData
{
public MySubsetData MySubsetData { get; }
}
Your view containing the DataGrid would be
<UserControl.DataContext>
<local:ViewModel>
</UserControl.DataContext>
<DataGrid ItemsSource="{Binding Path=MyDataCollection}">
<DataGrid.Columns .../>
<DataGrid.RowDetailsTemplate>
<DataTemplate>
<!-- each row of the items control has an implicit DataContext of MyData -->
<!-- so bind the DataContext of the subset control to MySubsetData -->
<local:MySubsetDataUserControl DataContext={Binding MySubsetData}/>
</DataTemplate>
</DataGrid.RowDetailsTemplate>
</DataGrid>
Now your subset control can look like
<UserControl>
<Grid>
<TextBox Text="{Binding Path=TextData, UpdateSourceTrigger=PropertyChanged}"/>
</Grid>
</UserControl>
On re-reading the question, maybe all I've done is repeat the Xaml from the question in a slightly different way.
However the various classes should be implementing INotifyPropertyChanged, e.g.
public class MySubsetData : INotifyPropertyChanged
{
public string TextData
{
get{...}
set{...; OnPropertyChanged("TextData"); }
}
}
Then the TextBox bound to the TextData property will reflect changes made in code.