I was reading this article - http://msdn.microsoft.com/en-us/magazine/dd419663.aspx
And I came across this piece of code in the WPF Demo application that came with the article.
This template applies a CustomerView to an instance of the CustomerViewModel class shown in the main window.
<DataTemplate DataType="{x:Type vm:CustomerViewModel}">
<vw:CustomerView />
</DataTemplate>
I substituted the angle brackets for square brackets - not sure how to post them.
The code is in the MainWindowResourses.xaml and the code starts on line 19.
Anyone know how I can do this in Silverlight ??
We don't have the DataType and I need to be able to tell the app that this View is associated with this ViewModel - so I can create a tab control with different view like the demo app.
Cheers,
EC
This is an example of WPF implicit styling, where a style is applied to all the controls in the project. This is not supported in Silverlight.
To get around this you need to instead place your view controls in the markup and set their DataContext to the viewmodel.
<Window.Resources>
<vm:CustomerViewModel x:Key="theViewModel">
<Window.Resources>
<vw:CustomerView DataContext={StaticResource theViewModel}/>
theViewModel doesn't have to come from the resources section, it could be a property in the hosting XAML control/page.
Related
I am a newbie in WPF. I was exploring MVVM Pattern for WPF applications. I am having trouble in binding Text property of a TextBox from VIEW to a variable in VIEWMODEL
Here is the TextBox from MainWindow.xaml
<TextBox x:Name="UsernameTxt" Grid.Row="4" materialDesign:HintAssist.Hint="Username"/>
I just need to know how to bind its Text Property to ViewModel Class in Class Library
Thanks
I think it's possible to give a very generic answer to this very generic question.
If the question changes context this answer is very likely to be deleted but here goes anyhow.
You want your viewmodel to be in the datacontext of the textbox. Because datacontext is inherited down the visual tree this usually means you want to set datacontext of your window to an instance of the viewmodel. Or maybe the usercontrol your textbox is in, but we know nothing about your app so let's just cover the simple scenario.
Your options are to instantiate a viewmodel using code or xaml.
If you look at this article:
https://social.technet.microsoft.com/wiki/contents/articles/31915.wpf-mvvm-step-by-step-1.aspx
That instantiates in xaml.
Note the xmlns is
xmlns:local="clr-namespace:wpf_MVVM_Step01"
That's saying where you see some bit of markup which is prefaced "local:" then go get the class out of this namespace.
To point to a different dll ( a class library ) you need to tell it which assembly. You do that by adding ;assembly=Whicheverdll to your equivalent of that xmlns. And of course that won't be local then so give it a different name. You also need a reference to that dll or project added to the entry point exe.
Once you've done all that and your viewmodel is instantiated into memory and in the datacontext of that textbox you need some sort of binding.
Which the article covers but that will be something like:
<TextBox Text="{Binding YourPublicStringProperty}"/>
How can I use the properties of the controls that are inside a user control without having to use DependencyProperty?
Since, if for example I want to use all the properties of a button, I would have to declare all these?
And if there is another way without user control and it is the correct one, I would appreciate it if you answered it. (Google translator, sorry)
UserControl:
<UserControl x:Class="UserControls.UserControl01"
...
>
<Grid>
<Button x:Name="uc_btn" />
<TextBox x:Name="uc_txt" />
<DataGrid x:Name="uc_dtg" />
</Grid>
</UserControl>
Code using the UserControl:
<Window x:Class="UserControls.wnd02"
...
>
<Grid>
<local:UserControl01 uc_btn.Background="Red" uc_txt.Margin="10" uc_dtg.BorderThickness="5" Margin="90" />
<local:UserControl01 uc_btn.Background="Green" uc_txt.Margin="25" uc_dtg.BorderThickness="20" Margin="5" />
</Grid>
</Window>
It is not usual to do what you are asking.
Let's consider a usercontrol which is intended to work as if it is one single control. For example a time picker. This contains two sliders which increase/decrease hour and minute. You can also overtype in the hour and minute textboxes and there's a : between the two textboxes.
This usercontrol is all about the one property though. Time. You don't care what the minutes background is externally. If this changes it's internal to the usercontrol.
In this scenario you'd usually add a TimeSpan dependency property to the usercontrol and this is the only thing anything external to it uses.
Pretty much all commercial WPF development uses the MVVM pattern and that TimeSpan would be bound to a property in the parent view's viewmodel.
That's one scenario.
Another is where a usercontrol encapsulates a bunch of UI which is then re-usable.
Styling has scope so when you apply a style to say a Button in a window then that would apply to any Buttons in a usercontrol within it. Setting their properties.
There are also certain dependency properties marked as "inherits" whose values propogate down the visual tree.
One such is DataContext and it is this which most teams would use to deal with properties within a usercontrol.
Using MVVM there would be a MainWindowViewModel.
That would have (say ) a ChildUserControlViewModel property. That would be associated with usercontrol using a datatemplate specified datatype.
You'd then bind properties of whatever is in a usercontrol to properties of ChildUserControlViewModel or properties of MainWindowViewModel using RelativeSource binding.
ViewModel first is a common navigation and composition pattern for WPF. You should be able to find numerous blogs explain it better than I can in a SO post.
Here's one:
https://social.technet.microsoft.com/wiki/contents/articles/30898.simple-navigation-technique-in-wpf-using-mvvm.aspx
In the above image, child is a ContentPresenter. Its Content is a ViewModel. However, its ContentTemplate is null.
In my XAML, I have a TabControl with the following structure:
<local:SuperTabControlEx DataContext="{Binding WorkSpaceListViewModel}"
x:Name="superTabControl1" CloseButtonVisibility="Visible" TabStyle="OneNote2007" ClipToBounds="False" ContentInnerBorderBrush="Red" FontSize="24" >
<local:SuperTabControlEx.ItemsSource>
<Binding Path="WorkSpaceViewModels" />
</local:SuperTabControlEx.ItemsSource>
<TabControl.Template>
<ControlTemplate
TargetType="TabControl">
<DockPanel>
<TabPanel
DockPanel.Dock="Top"
IsItemsHost="True" />
<Grid
DockPanel.Dock="Bottom"
x:Name="PART_ItemsHolder" />
</DockPanel>
<!-- no content presenter -->
</ControlTemplate>
</TabControl.Template>
<TabControl.Resources>
<DataTemplate DataType="{x:Type vm:WorkSpaceViewModel}">
....
WorkSpaceViewModels is an ObservableCollection of WorkSpaceViewModel. This code uses the code and technique from Keeping the WPF Tab Control from destroying its children.
The correct DataTemplate - shown above in the TabControl.Resource - appears to be rendering my ViewModel for two Tabs.
However, my basic question is, how is my view getting hooked up to my WorkSpaceViewModel, yet, the ContentTemplate on the ContentPresenter is null? My requirement is to access a visual component from the ViewModel because a setting for the view is becoming unbound from its property in the ViewModel upon certain user actions, and I need to rebind it.
The DataTemplate is "implicitly" defined. The ContentPresenter will first use it's ContentTemplate/Selector, if any is defined. If not, then it will search for a DataTemplate resource without an explicit x:Key and whose DataType matches the type of it's Content.
This is discussed here and here.
The View Model shouldn't really know about it's associated View. It sounds like there is something wrong with your Bindings, as in general you should not have to "rebind" them. Either way, an attached behavior would be a good way to accomplish that.
I think the full answer to this question entails DrWPF's full series ItemsControl: A to Z. However, I believe the gist lies in where the visual elements get stored when a DataTemplate is "inflated" to display the data item it has been linked to by the framework.
In the section Introduction to Control Templates of "ItemsControl: 'L' is for Lookless", DrWPF explains that "We’ve already learned that a DataTemplate is used to declare the visual representation of a data item that appears within an application’s logical tree. In ‘P’ is for Panel, we learned that an ItemsPanelTemplate is used to declare the items host used within an ItemsControl."
For my issue, I still have not successfully navigated the visual tree in order to get a reference to my splitter item. This is my best attempt so far:
// w1 is a Window
SuperTabControlEx stc = w1.FindName("superTabControl1") as SuperTabControlEx;
//SuperTabItem sti = (SuperTabItem)(stc.ItemContainerGenerator.ContainerFromItem(stc.Items.CurrentItem));
ContentPresenter myContentPresenter = FindVisualChild<ContentPresenter>(stc);
//ContentPresenter myContentPresenter = FindVisualChild<ContentPresenter>(sti);
DataTemplate myDataTemplate = myContentPresenter.ContentTemplate;
The above code is an attempt to implement the techniques shown on the msdn web site. However, when I apply it to my code, everything looks good, except myDataTemplate comes back null. As you can see, I attempted the same technique on SuperTabControlEx and SuperTabItem, derived from TabControl and TabItem, respectively. As described in my original post, and evident in the XAML snippet, the SuperTabControlEx also implements code from Keeping the WPF Tab Control from destroying its children.
At this point, perhaps more than anything else, I think this is an exercise in navigating the Visual Tree. I am going to modify the title of the question to reflect my new conceptions of the issue.
What I'd like is a control that functions just like the tab control but instead of having the tabs along the top, the items would be displayed in a list box along the side. I imagine it's possible but haven't found any examples, I'm hoping there's someone here that's done something like this.
WPF controls are designed to enable exactly what you want. To reuse control functionality while completely replacing the visual representation. You will have to create your own ControlTemplate for the TabControl. You can find a TabControl ControlTemplate Example on MSDN. You will also have to study the Control Authoring Overview on MSDN.
I actually find the Silverlight 3 documentation somewhat easier to digest, and even though there are some differences when it comes to control styling the fundamental concepts are still the same. You can read Customizing the Appearance of an Existing Control by Using a ControlTemplate on MSDN to learn about control templates and then study TabControl Styles and Templates to discover what is required to create you own control template in Silverlight.
You can use Expression Blend to extract the the default TabControl template in WPF.
You don't need to use a TabControl at all. You could just bind your ListBox to a list of items, and put a ContentControl beside it, bound to the selected item :
<DockPanel>
<ListBox Name="listBox"
DockPanel.Dock="Left"
ItemsSource="{Binding Items}"
DisplayMemberPath="Name"/>
<ContentControl Content="{Binding SelectedItem, ElementName=listBox}"
ContentTemplate="{StaticResource theTemplate}"/>
</DockPanel>
I'm working on a Silverlight templated control (i.e. it derives from Control and has its look implemented as a ControlTemplate in generic.xaml) and came across the need for a ValueConverter in one of my bindings. Normally I'd just create an instance of the ValueConverter in the Resources of the control working with but I can't figure out how to do that with a ControlTemplate. I'd like to keep this implementation all in Xaml if possible, but I suppose I could override OnApplyTemplate and manually create the binding with a converter.
This does work in Silverlight 3. You just need to add a resources section inside your Control Template, and add the ValueConverter to the template's resources:
<ControlTemplate TargetType="controls:MyControl">
<Grid Margin="8,40,8,20" x:Name="peopleListContainer">
<Grid.Resources>
<controls:MyValueConverter x:Key="converter" />
</Grid.Resources>
<!-- ....
However, ValueConverters are often misused in Control Templates. You may want to use a TypeConverter instead. Bryant Likes wrote a good article discussing the difference between ValueConverter and TypeConverter in this scenario.