So far my plan is to have an event "Item selected" which the property inspector listens to. The actual property inspector is just a ContentControl. When the object is selected the content property is set and the appropriate DataTemplate for editing the object is loaded.
In general I am trying to do this "MVVM" style. I guess you could use reflection instead of templating but I only have a handful of types so far.
Has anyone implemented something similar?
Can you offer any advice or source code?
Basically, what you're looking for is a PropertyGrid... have a look at this : http://www.codeplex.com/wpg
If you want to do this MVVM style, then instead of having a ItemSelected event and using code to set the inspector's content, have a SelectedItem property in your viewmodel, and bind the inspector's Content to that property:
<ContentControl Content="{Binding SelectedItem}" />
How you update the SelectedItem will depend on the nature of your view and model. For example, if the items are displayed in a Selector control like a ListBox, then you would just two-way bind the Selector.SelectedItem to the viewmodel's SelectedItem.
Have a look at the WPF Inspector project. It's a spy utility like Snoop but it also includes a feature to debug triggers.
Related
i've got a textbox which text is binded to a listview selecteditem as follows:
<TextBox x:Name="txtAdditional" Width="300" Text="{Binding ElementName=lstPersons, Path=SelectedItem.Additional, Mode=OneWay}" />
Now i like to implement a mechanism to add new items to the listview using this textbox to get the actual data. So i would like to bind the text of the textbox to a property of the viewmodel so it can be processed by a command.
So it the textboxes text has to be binded to the listviews selecteditem and additionally to a property of my viewmodel.
I've searched around and found some approaches but i can't help to think that there should be some simpler mechanism to archive this goal.
What I found by now:
Using MultiBindung with some kind of ValueConverter? So it seems to me that this is primary for displaying and not for updating a viewmodels property.
The use of some selfdefined custom control?
The use of an BindingProxy with in- and out-dependencyproperties like in Impossible WPF Part 1: Binding Properties?
Is there another, simpler solution to this or would i have to use one of those above?
And if one should use one of those approaches, which one whould you choose?
I can't help but thinking that this issue hasn't been given some thoughts already, using an mvvm pattern?! ;-)
yes thanks to the hint from BionicCode.
We, or better I should have to think the MVVM concept out. Of course no - or at least as little code behind as possible.
I added the property "selectedPerson" to my viewmodel and bound the SelectedItem of the listview to this property. So the object related properties were at hand directly through the "selected" object in my viewmodel and there was no need anymore to access the textbox content at all.
Thanks to BionicCode for the hint!
I have an application that uses Caliburn.Micro. My View contains a user control which contains e.g. a tab control. I want to be able to access that tab control from the outer ViewModel to select a particular tab. Is it possible?
Thanks.
The standard MVVM way is to have the TabControls SelectedItem property bound to a property on your viewModel.
<TabControl ItemsSource="{Binding PropertyToYourViews}"
SelectedItem="{Binding PropertyToYourSelectedView}">
</TabControl>
If you do it this way your ViewModel does not have to know about the existence of the TabControl.
The next step is dependant on your implementation. Your outer ViewModel could simply keep a reference to the child viewModels SelectedView property and access it directly however,
If you want to keep your ViewModels decoupled then you will need to implement some sort of notification system. I'm not sure of the specifics of Caliburn.Micro but most MVVM frameworks offer some kind of solution for this.
Implementation would depend on exactly how you have it set up, but you can bind a variable in your view model to the SelectedItem of the TabControl
I implemented some generic CustomControls in WPF, for instance an AutoCompleteTextBox.
Now, I'd like to implement a generic ViewModel library, in order to perform the databind of these controls.
Now I defined one attached property named CDataSource, that specifies the source of the data to bind within the control.
My question is : Is it possible, that the CustomControl passes to the ViewModel the CDataSource value? In this way the ViewModel may populate the control on the basis of the CDataSource property.
Thanks in advance
This seems like a strange request to me. You don't want any dependency on your view model from within your custom control. Instead, you would normally have a dependency property on your custom control which is the ItemsSource, and then you would set the value of this from your view in XAML.
This is how the AutoCompleteBox included in the WPF Toolkit operates.
I have a dependency property on my ViewModel which is the DataContext for my View. The ViewModel has no reference to the View. The property on the ViewModel is going to reference a control on the view, but I need to be able to set this property in XAML.
How is this possible? One thought I had was to develop a custom control which has a Property property and a Value property, so you could do something like this in the View to set the property on the ViewModel:
<PropertySetter Property="{Binding MyViewModelDependencyProperty}" Value="{Binding ElementName=aControlOnMyView" />
Before I went down this route, I wanted to check if there was any other approach I could take?
Thanks for the detailed reply Ray, but if I give you a bit more detail about the problem I'm trying to solve, you might get a better idea of why I mentioned the approach I did.
Basically, what I'm trying to do is set the focus to a textbox when the user hits a button. I've written an attached property which you can attach to the Button control, specify what the trigger event is (in this case the 'Click' event), and then what control to focus on. This works really nicely, and keeps everything in XAML.
However, I now have a use case where the focus should be set to an arbitrary text box from the click event on a button which is part of a toolbar. This toolbar is itself a user control which is sitting inside another user control, which is inside another user control! This toolbar needs to be reusable across various different forms, and each time, the control to set focus on after you click the button will be different per form.
That's why I had the idea of making the focus control (i.e. a textbox) a property on the view model itself (on my ViewModel base to be precise), and have the ViewModel base code (which the toolbar is bound to), set the focus to the control when the button is clicked (and the e.g. Add/Edit method is called on the ViewModel base).
In unit test land, the control to focus on property will be null, so it's .Focus() method just won't be called. So I can't see an issue there. My problem is then how you set the focus control property from XAML, which is why I had the PropertySetter idea.
I don't like the fact that the ViewModel has any reference to controls sitting on the view, but I can't see another way to achieve what I need. What if the logic that dictates whether to set focus to the control is quite complex? This would sit in the ViewModel surely? Therefore, is there any harm in the ViewModel having this UIElement property? It still knows nothing about the specific View it is bound to, it just knows that there is a control which it needs to set focus to when some action happens on the ViewModel.
My first reaction (and it's a strong one) is so say "Don't do that!" By giving your view model a reference to a part of your UI you are breaking the encapsulation that makes view models so powerful and useful.
For example, what if you want to unit test your view model or serialize it to disk? In each case the piece of your UI will not be present, because there will be no view at all. Your tests will miss coverage and your reconstitution will be incomplete.
If your view model actually needs references to UI objects and there is no better way to architect it, the best solution is to have the view model itself construct those controls it requires a reference to. Then your view can incorporate that control as the Content of a ContentPresenter via binding and provide a Style to configure the control, including a ControlTemplate to provide its content. Thusly:
public class MyViewModel
{
public ListBox SpecialControl { get; set; }
public MyViewModel()
{
SpecialControl = new ListBox();
}
}
and
<DataTemplate TargetType="{x:Type local:MyViewModel}">
<DataTemplate.Resources>
<Style TargetType="ListBox" ... />
</DataTemplate.Resources>
...
<ContentPresenter Content="{Binding SpecialControl}" />
</DataTemplate>
Other possibilities are:
Have the view model actually derive from the Control class, then override OnApplyTemplate() and use GetTemplateChild to find a template item whose name starts with "PART_"
Implement an attached property that takes a property name, finds that property in the DataContext, and sets it to the DependencyObject to which the property is attached.
Implement your PropertySetter idea
My option #2 would look like this:
<DataTemplate TargetType="{x:Type MyViewModel}">
...
<TextBox local:PropertyHelper.SetViewModelToThis="SpecialControl" />
...
</DataTemplate>
The code in the SetViewModelToThis PropertyChangedCallback would get the view model from the DataContext, reflect on it to find the "SpecialControl" property, then set it to the TextBox. Note that the implementation of SetViewModelToThis must take into account the possiblity that DataContext is not set right away, and that it maybe changed requiring the old setting to be removed and a new one made.
First of all, the DataContext of the control should be the ViewModel object and not a property of it. Second, when you TwoWay bind a property of ViewModel to your control, changes in the control's value will update (in your case, 'set') the value of ViewModel's property.
HI Can any one suggest me how bind viewmodel to a usercontrol..
Also please share different way of doing that..
I have added viewmodel and view into my xaml file in namespace and in the user control resource tag.. i have defined a data template with data type as the viewmodel wh i have wrote.. inside that i have added my view (i mean the same usercontrol ih which im editing now is it possible -- please let me know).. I have used content control with content={Binding}.. and contenttemplate as a datatemplate.. in that i have reffered the property which i want to bind from viewmodel).. but its not binding as such..
My query is different ways of binding viewmodel to view in UserControlLibrary Project ?
Sdry's right, you can also set the DataContext property of your view to your ViewModel.
Also, here's a WPF databinding cheat sheet that will likely come in handy: http://www.nbdtech.com/Free/WpfBinding.pdf
Set the datacontext of your view, with an instance of your viewmodel. Throughout your view you can then bind to the properties of your viewmodel with "Path" in the binding.