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.
Related
Here is my situation. I have a View and a ViewModel. The view's DataContext is set to the ViewModel. Due to the use of a 3rd party control, I am forced to put some code in the code-behind. In the code-behind I create an object called StraightConnectorTool.
In my View, I need to bind to this object. If the View's DataContext is set in the code-behind:
DataContext = this;
The following binding works fine.
<BarItemToolBehavior ActiveTool="{Binding ActiveTool, ElementName=diagram, Mode=TwoWay}"
Tool="{Binding StraightConnectorTool}"/>
Where diagram is the name of the 3rd party control on the View and ActiveTool is one of it's properties.
However, if the View's DataContext is set to the ViewModel, the binding doesn't work. I'm stuck trying to figure out how to bind to the view when it's DataContext is set to the ViewModel. Any ideas?
It's not good practice, but you can bind the BarItemToolBehavior's DataContext to the view. Either by name in the code behind or in XAML using RelativeSource FindAncestor to find the view. A better solution would be to move that object to the VM where it belongs.
I have a UserControl with 4 combobox bound to collections in viewmodel for that usercontrol.
I have used this control in a wpf form. This wpf form has its own viewmodel.
How do i access the text from the 4 comboboxes within the wpf form's viewmodel?
EDIT: i saw that you have different viewmodels. now it depends of the use of your usercontrol and the use of mvvm:)
you can use messenger or eventaggregator to comunicate the seleteditems from usercontrolviewmodel to mainviewmodel.
you can also use RelativeSource binding in your usercontrol to bind the selecteditem to your mainviewmodel directly (usercontrol then is just a composition of controls).
you can can rid of the usercontrol viewmodel and put all in the mainviewmodel and take my old example
you can create DependencyProperties for the SelectedItems in your usercontrol!(not usercontrol viewmodel!) and bind these to the properties in your mainviewmodel. i think thats the cleanest way if the usercontrol should be a real usercontrol.
old example:
in your viewmodel: //the real code should of course implement INotifyPropertyChanged and raise it properly
public ObservableCollection<string> MyFirstCollection {get; set;}//init once, add,remove,clear to alter
public string MySelectedCombobox1Value {get;set;}
in your usercontrol:
<ComboBox ItemsSource="{MyFirstCollection }" SelectedItem="{Binding MySelectedCombobox1Value, Mode=TwoWay}" />
thats all relating to your question. be sure that you set the DataContext right. you can check this with tools like snoop. the code i posted expected that the dataconext for the combobox is the viewmodel.
The UserControl should inherit the data context of the form you're adding it to which would be the view model. Any bindings in the UserControl would then be relative to the inherited data context. Have you tried binding to a view model property to ComboBox.Text?
UPDATE
Sorry, misread your question. Didn't see that the user control already has its own view model.
While it seems like there's a better approach, you could expose dependency properties on the user control that exposé the text of each combobox. Just thinking out loud.
The only clean way to do this is with binding, and the only way that would be recommended is if the user control exposes a DependencyProperty for the ViewModel or the individual text properties (as was suggested by sellmeadog) for consumption. Then you can have a property in the parent ViewModel that binds directly to that Dependency Property.
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.
In Silverlight I've a page with some controls and a listbox.
I'm using MVVM and the dataContext of the listbox is defined like this. In my model I have a property ProductCommand and this ProductCommand object contains a list of product named Products.
My listbox is in a grid with the datacontext defined as the ProductCommand property. and the databinding for the listbox is set to the Products (Binding="{Product, Mode=twoWay}").
In my model class I also have a selectedProduct property, and I want to bound it to the SelectedItem property of the listbox.
How can I do that?
I have had similar problems I found this blog article by Dan Wahlin on a Data Context Proxy very helpful.
Of course in Silverlight 5 ancestor binding will also provide you a means to solve this issue.
I have a tab control where each TabItem is a UserControl. I'd like to hold the UserControls in the TabControl's ItemsSource. Does ItemsSource list go in the Window's ViewModel? If so, I feel like it's breaking MVVM since the ViewModel would now have GUI controls within it. Or do I put this list in the codebehind of the window that holds the tab control?
Any suggestions would be great!
With tab controls, more often than not the individual tabs are created statically in XAML rather than at run time by data binding. However there is no reason why you shouldn't do this. If you have a collection of views, they should definitely be stored in a view.
Bear in mind that you could also bind the ItemsSource to a list of ViewModels objects and WPF will generate a view for you with the ItemTemplate, with the ViewModel object set as the DataContext. This collection of ViewModels should be stored in a view model, although at some point a view model will obviously have to be stored in a view.
This can most likely be done in a number of ways, all which are up for debate on how "MVVM-friendly" they are.
My setup looks like the following.
My Main window has a DataContext bound to a MainWindowViewModel which contains an property
public ObservableCollection<Workspace> WorkspaceCollection{get;set;}
MainWindow has a TabControl which ItemsSource is bound to WorkspaceCollection
Workspace are all viewmodels and are bound to different views/usercontrols via DataTemplates
You might have a look at the Write sample application of the WPF Application Framework (WAF). It has a TabControl where each TabItem is a UserControl and it does this by applying the MVVM pattern.
Here's what I've done.
I created an interface that all of my controls implement, IMyAppControl, which has some information such as Title, Description, other metadata.
My Main Window has an ObservableCollection that the tab ItemsSource binds to.