I created an UserControl that consists of a TextBox and a Label controls. I created another UserContol that inherits the first, on which I added a Button. The difficult that I’m experiencing is that I can’t access directly from secondary UserControl properties like TextBox.Text that are in the primary UserControl. Is there a easy way to access properties from the primary UserControl or the only way is to create a public methods, like a “GetText()”, where I return the TextBox.Text property?
I assume you are talking about WPF.
Xaml view you can use x:FieldModifier="Public"
<Button x:Name="MyButton" x:FieldModifier="Public" />
Note that accessing inner controls is not best practise, your code should not care what controls view contains. If you want for example make button disabled create property in code behind and bind buttons IsEnabled to that property instead
Related
There are lots of questions like this one, but still can't get what I really want, and all of them have something that differs of mine and that is:
I have a UserControl:
Built separately in a class library project called UCProject;
The project UCProject has a View for the control, and its ViewModel;
The UserControl binds some of its own controls and UIElements properties in the View to properties declared in the ViewModel in, of course, the UCProject;
How can I show or expose or make the ViewModel Properties accessible to the page or the window of the project (that may be called for instance GlobalProject) that may host this UserControl;
I'am building this UserControl, I want to build events, properties to it ... and I want it to be used by others as a given assembly to them, so its code is not accessible, they only can consume it, I want to respect the MVVM pattern, and I don't have a clear idea how to realize that, should I write this properties and events in the CodeBehind of the UserControl View or should I put them in the ViewModel, and in that case how can I access them from outside, just like we daily use third-party controls
If i assume it right, you want to expose properties of child UserControl's ViewModel to containing parent root element which might be window or other UserControl.
There are two approaches to it:
First, DataContext DP is inheritable i.e. child controls inherit it from parent control unless set it explicitly to some other value. So, what you can do is have common ViewModel and set it as DataContext on parent UserControl and both have access to its properties.
Second, in case you want separate ViewModels for parent and child UserControls. You can always access properties of child's ViewModel via DataContext. Let me explain with an example:
<UserControl x:Name="ParentUserControl">
<StackPanel>
<local:ChildUserControl x:Name="Child"/>
<TextBlock Text="{Binding DataContext.PropertyName, ElementName=Child}"/>
</StackPanel>
</UserControl>
where PropertyName is property in ViewModel of ChildUserControl.
Here as you can see TextBlock which lies in ParentUserControl is binding to property in ViewModel of child UserControl.
You haven't specifically declared which parts of these projects you have control over so I'll assume you can changed all of them. Basically you need to use dependency properties in the User Control. First you bind the view to the ViewModel, when you add the User Control to the view it will effectively inherit the DataContext and you can bind the dependency properties you've created to the various parts of the ViewModel. In the User Control itself you bind the various FrameworkElements to the dependency properties in the User Control, not to the ViewModel itself.
Make sense?
I had to implement those Properties in the CodeBehind using DependencyProperties that's the best way to do it
I am creating some custom user controls for WPF. This user controls contain custom dependency properties so I can fill them in the designer.
One of this properties is called "InnerUserControlType". This dependency proeprty is a custom enumeration containing some values like TextBox, ComboBox, Label, CheckBox, etc.
I would like to be able to set this property in my XAML pages in the designer and then see the user control change the displayed inner control depending on the property.
How should I implement this? The grid which will contain the inner control in my user control is a normal field, so it cannot be accessed from a static method property (like the dependency properties).
I want it to have it working in the designer so the designers can work easily.
Thanks a lot!
Put a ContentControl in the grid, bind the Content property to the UserControl via relative source
<ContentControl Content="{Binding RelativeSource={RelativeSource FindAnsector,
AncestorType={x:Tyle myNamespace:MyControl}}}"
and make a DataTemplateSelector that will check the value of InnerUserControlType and will return an appropriate data template containing the control that was asked for in the property.
Depending on your scenarios, you might need to make sure the controls in the data template have the right data context. If the data context of the controls should be the same as of the user control, then on the root element in the data template, add relative binding for data context. Something like (for the text box data template):
<TextBox DataContext="{Binding DataContext,
RelativeSource={RelativeSource FindAnsector,
AncestorType={x:Tyle myNamespace:MyControl}}}"
......
</TextBox>
EDIT:
I've noticed only the wpf tag and missed the silverlight one.
In Silverlight you don't have ...TemplateSelector properties, so use a converter instead.
I am building a custom UserControl which would allow me to place text inside a ProgressBar. The problem is, none of the ProgressBar's DependencyProperties get transferred over. Here is the XAML for my custom UserControl.
<UserControl
x:Class = "MyProgram.MyCustomProgressBar"
xmlns = "http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x = "http://schemas.microsoft.com/winfx/2006/xaml" >
<Grid>
<ProgressBar Name="uiProgressBar" />
<Label Name="uiLabel" />
</Grid>
</UserControl>
How can I access and set the Minimum, Maximum, Value, etc. from XAML when I start using this UseControl.
<local:MyCustomProgressBar x:Name="uiLoadTime" ??.uiProgressBar.Maximum="50" />
I am hoping I don't need to redefine a bunch of DependencyProperties in order to get this functionality.
The usual way is to use a DependencyProperty... it's not so bad once you got used to it really.
Use the "propdp" built in snippet in the code-behind of your usercontrol.
Let's take the ProgressBar.Maximum example:
Make an integer dependencyproperty with a default value of 100 (or whatever you like), name it InnerProgressBarMax.
In your UserControl's XAML, you bind it this way:
<ProgressBar Maximum="{Binding InnerProgressBarMax, ElementName=myUsrCtrl}" />
When you use the control in another part of your application, simply enter a value like this:
<local:MyCustomProgressBar x:Name="uiLoadTime" InnerProgressBarMax="50" />
Rinse & repeat for each property you want to expose.
Edit:
If you really need to have 50+ DP exposed, you could bring down the hastle by specifying smart default values for your DPs.
To do that, when you create a DP, set the parameter of new PropertyMetadata(YOUR_DEFAULT_VALUE)
Once that is done, your control may expose many DPs, but you'll only have to set a few manually in the XAML code that uses the control.
The alternative to wrapping everything in DependencyProperties is to let the UserControl's consumer provide the ProgressBar. It could look like this:
<local:MyCustomProgressBar x:Name="uiLoadTime">
<local:MyCustomProgressBar.ProgressBar>
<ProgressBar Maximum="50" />
</local:MyCustomProgressBar.ProgressBar>
</local:MyCustomProgressBar>
Then in MyCustomProgressBar.xaml.cs, you would expose a public property for a ProgressBar. In its setter, modify the properties however you see fit, then add it to the UserControl's root Grid.
I am trying to creating a combobox with checkboxes on each line to allow multiple selecting. Would this be better as a User Control or Custom Control?
I haven't created a control before so just looking for a little advice on what direction I need to head.
Thanks.
UserControl (Composition)
Composes multiple existing controls into a reusable "group"
Consists of a XAML and a code behind file
Cannot be styled/templated
Derives from UserControl
CustomControl (Extending an existing control)
Extends an existing control with additional features
Consists of a code file and a default style in Themes/Generic.xaml
Can be styled/templated
The best approach to build a control library
In your case, I think UserControl would be better; here's an example for you:
<CheckBox Content="Property" IsChecked="{Binding Path=SomeProperty}" />
<ComboBox IsEnabled="{Binding Path=Enabled}" />
I would say use a datatemplate.
Like this: Looking for a WPF ComboBox with checkboxes
It's a lot more simple than trying to create your own control. :)
I may be making this more complicated than necessary ... but here goes.
I have my MainPage.xaml, in there I have references to two other UserControl's, ResultsView, and DetailsView.
Inside of the ResultsView, I have a ListBox bound to an ObservableCollection of custom items, I have a DataTemplate that is rendering each item. The item has a CaseID, and when I click on it, it's displayed as a HyperlinkButton, I need a Command I've set in the MainPageViewModel to fire, which handles changing the visibility to hide the ResultsView, and show the DetailsView.
How do I bind the Command of the Hyperlinkbutton to the Command located in my MainPageViewModel?
Thanks in advance!
edit for clarification:
MainPage.xaml
<resultsView:ResultsView/>
<detailsView:DetailsView/>
Each of the two views (ResultsView & DetailsView) have their own ViewModel. So I'm going from my DataTemplate which resides in a ListBox inside my ResultsView, I need to go up to the MainPageViewModel, an extra step than your answer mentioned. Tried your method naming my MainPage.xaml to Name="mainPage", and using that as the ElementName in my HyperlinkButton, but no luck. I'll do some research on the RelativeSource option and see if I can make that work.
Thanks for your help so far.
edit 2: Forgot to add that the DataTemplate is in a ResourceDictionary, not in the ResultsView.
Well, it depends on the specific details, not all of which you've told us, but I can give you some examples.
Let's say that your DataTemplate for the custom items resides in the XAML of the ResultsView user control. That's a good spot for it but you might have put it in a resource dictionary.
As you say, the ListBox is bound to the collection of custom items. Let's further assume that the custom items collection is itself a property in your MainPageViewModel. And you've said clearly that the command you want to bind to is also in MainPageViewModel.
So the problem, which is a very common one, is that you are working inside a template associated with a binding to a collection, and so your DataContext is a custom item. It is no longer the main view-model itself. That's great as you show appropriate properties of the custom item like CaseID. But it's not great when you want to escape to the top-level of view-model.
If what I've said is true, then the ResultsView user control is in fact probably bound to the MainPageViewModel because you haven't "drilled into" the custom items collection yet. So, what you need to do is find a way using the binding syntax to reference the ResultsView user control from inside the DataTemplate for the ListBox. If you can do that, then you've escaped the collection.
There are two main approaches to do this:
ElementName syntax
RelativeSource syntax
I'll describe ElementName syntax and you can look up the other one.
Part 1) Name your ResultsView UserControl element like this:
<UserControl ....
Name="resultsView">
<!-- ... -->
Part 2) Inside your DataTemplate where you are defining the appearance of the hyperlink use the ElementName syntax to refer to that element:
<TextBlock>
<Hyperlink Command="{Binding DataContext.ItemDetailsCommand, ElementName=resultsView}"/>
</TextBlock>
So first we use ElementName to get the ResultsView UserControl element, and then we have a path with two pieces: the first piece is the DataContext property of the ResultsView which gives us the MainPageViewModel (yeah!), and then the property of the command we want to invoke.
That's one way to "escape" the binding and issue commands found at a higher level in the view-model.