Based on this mechanism, I created a dialog window of which I can dynamically assign the content by a <ContentPresenter Content="{Binding .}">
The content I want to assign is an user control with a corresponding ViewModel. This works as I can render the DialogView in other usercontrols
<DataTemplate DataType="{x:Type ViewModels:DialogViewModel}">
<Views:DialogView/>
</DataTemplate>
)
However, in the DialogWindow, DialogView cannot be rendered but instead, only the string representation of DialogViewModel is visible. What might be the reason why I cannot render the view of contentpresenter's content?
Any help is much appreciated!
Thanks in advance
Where did you define the Data Template? It sounds like you are creating them as Window resources, and did not include it in your DialogWindow. If you're defining them as Window resources, the Data Template definition needs to be included on every Window you want to render this way. If the ViewModel/View pair is global to the application, it is easier to just define it in the App.xaml where it will be picked up by any Window or UserControl throughout the application.
Related
I am working on a an WPF MVVM application where I need to have a Main Window with just a logo and it has to show child views inside it. I don't have any controls in Main Window all the controls reside in child view for example Buttons like Next, Back, Cancel and some text blocks etc. Now If users select Next button on the child view I have to draw or load the next child view inside the Main Window. If Back button is clicked I have to go back to the previous child view. So basically I am changing the child views depending on which button is clicked. Also I am maintaining different view models for every child view. Now the problem is I am not able to figure how should I link the child views to there respective view models. This application is similar to some Installation applications where different dialogs are shown depending on the selection and the button clicked by the user.I am new to this wpf and don't want to use MVVM Light , Prism etc. Any detailed help will be greatly appreciated. Thanks in advance.
One of the easiest ways to associate any data type with XAML controls is to use a DataTemplate. Therefore, you can simply add something like this into your Application.Resources and as long as you do not set the x:Key properties on the DataTemplates, then they will be explicitly applied by the Framework whenever it comes across instances of your view models:
<DataTemplate DataType="{x:Type ViewModels:HomeViewModel}">
<Views:HomeView />
</DataTemplate>
...
<DataTemplate DataType="{x:Type ViewModels:MainViewModel}">
<Views:MainView />
</DataTemplate>
Then displaying the view is as simple as this:
<ContentControl Content="{Binding YourViewModelProperty"} />
In code behind, or your view model:
YourViewModelProperty = new MainViewModel();
It's often handy to create a base class for your view models and then the YourViewModelProperty can of that type and you will be able to interchange them using the same property and ContentControl.
UPDATE >>>
The general idea is that you have one MainViewModel class with one BaseViewModel property data bound to one ContentControl in MainWindow.xaml... the navigation controls should also be in MainWindow.xaml and not in the views themselves. In this way, the MainViewModel class is responsible for changing the property to the relevant view model instances when it receives navigation Commands from the MainWindow.xaml.
I explain my issue as I'm quite new to UI design :
I have a main View which displays a TreeView on its left part. When an element is selected I'd like to show a description of the Item on the right on the same window. The design of this description depends on the nature of the Item.
So I created a View per Item Type corresponding to the different possible design.
Now When I click on the TreeView I have no idea how to show the corresponding view on the right of the same window. (I'm not asking about catching the event, just displaying a view within another view, like if I dynamically plotted a control).
Is it possible ? If not what kind of approach would you suggest ?
Many Thanks.
This seems like a great candidate for a Data Template.
Basically, create a content presenter and bind its content property to the TreeView's SelectedItem property. Now, create data templates for each of your types (using the DataType property) in the ContentTemplate property.
Now, the correct data template will be chosen with the correct data whenever you select something in your tree view.
As far as a separate dispatcher goes, I'm not sure, but I'm also not sure what scenario would require one.
More information can be found in this SO question.
Sample:
<ContentPresenter Content="{Binding Path=SelectedItem, ElementName=TreeView}">
<ContentPresenter.ContentTemplate>
<DataTemplate DataType="{x:Type Type1}">
<!-- Bunch of stuff-->
</DataTemplate>
<DataTemplate DataType="{x:Type Type2}">
<!-- Bunch of stuff-->
</DataTemplate>
</ContentPresenter.ContentTemplate>
</ContentPresenter>
I have a WPF interface that has a panel used for displaying details about the particular option you have selected from a button bar. Eg if you click the Info button, the detail pane populates with a InfoDetailUserControl. If you click the Graph button, it populates with a GraphDetailUserControl.
The way I am doing this is to define each detail panel as a UserControl. I then have a ViewModel for each UserControl that drives the data. The detail panel is represented by a ContentControl and to display the relevant panel, I set the content of this to the ViewModel representing the UserControl I want to display. I then have a number of DataTemplates that map a ViewModel to a UserControl, so that when you add the VM to the ContentControl, it looks up the datatemplate for that type and displays the relevant UserControl.
Example datatemplates.
<DataTemplate DataType="{x:Type RunResults:SimpleCalcInfoResultViewModel}">
<Views:SimpleCalcInfoResult />
</DataTemplate>
<DataTemplate DataType="{x:Type RunResults:TradeResultViewModel}">
<Views:TradeResult />
</DataTemplate>
<DataTemplate DataType="{x:Type RunResults:GraphResultViewModel}">
<Views:GraphResult />
</DataTemplate>
<DataTemplate DataType="{x:Type RunResults:NoResultViewModel}">
<Views:NoResult />
</DataTemplate>
This all works fine, but the problem is that every time you change the content of the detail panel, you supply it the ViewModel class and it then on-the-fly looks up the datatemplate that matches the VM type and creates an instance of that UserControl. It then discards that UserControl when you switch to a different type. Hence if you keep switching between Info and Graph view for example, it keeps recreating the GraphUserControl every time you go back to it, it doesn't cache it from the first load and just redisplay the same view again.
The problem I have is that the Graph UserControl takes 3-4 seconds to initialise, in the InitializeComponent() call. I'm assuming this is just the WPF toolkit chart control being slow but it means the user must wait 4 seconds every time they go back to the Graph view, which is not ideal.
Is there a way I can either easily cache the first UserControl created so it only ever goes through that initialisation once or is there a way I can simply speed up the loading of the Chart control?
Many thanks
I am new to WPF and MVVM, and would appreciate help with the following problem.
I want to create an application in which a user specifies – through a dialog - how he would like to layout N number of chart objects on a page, and the application shows him this layout on a canvas. When satisfied with the layout he sees in the canvas, the user persists it for later use.
All chart objects can be visualized as rectangles. User can also define a header, which too is a rectangle.
A typical layout could be the header at the top of the page, below which are three charts side-by-side. User would be able to specify this layout as well as dimensions and location of each child in a dialog, and then hit the ‘Apply’ button expecting to see this specification in graphical form on the canvas.
In my view model I would have a tree where the parent is the canvas, having one child of type header, and 3 children of chart type.
The user might not like what he sees, and make changes in the dialog which would then effect changes in the view model.
I kind of understand the View-ViewModel interaction between the dialog and the view model. But don’t know how to implement the Canvas-ViewModel interaction. Meaning that when the user requests in the dialog say a header rectangle of a given size at a given coordinate, I know how to add that header object in the tree in the view model, but I do not know how to then update the canvas from the ViewModel's tree. How would the canvas get drawn to reflect the object tree in the viewmodel, and then get re-drawn each time the viewmodel changes (as a result of user's interaction with the dialog)?
One option is to add the viewmodels to a collection, and then bind those to an ItemsControl. If you provide the appropriate datatemplates in the XAML, the views are automatically bound to the data. The Itemscontrol I have looks like this:
<ItemsControl x:Name="WorksetPresenter"
ItemsSource="{Binding ElementName=RootWindow, Path=TableauItems}"
>
<ItemsControl.Resources>
<DataTemplate DataType="{x:Type viewModels:AnalysisViewModel}">
<wg:AnalysisView DataContext="{Binding DescriptiveAnalysis}"/>
</DataTemplate>
<!-- more datatemplates for more view/viewmodel pairs -->
</ItemsControl.Resources>
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<Canvas />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
</ItemsControl>
TableauItems is an ObservableCollection<>. As soon as an ViewModel is added to the collection, it is rendered on the Canvas according to the View specified in the datatemplate. For positioning you can use e.g. the Canvas.Left and Canvas.Top properties (mind the alignment!), or a rendertransform.
You shouldn't store graphical settings such as size and coordinates of your controls in your viewModel.
If I were you I would approch this a bit differently.
In the View, Use DragAndDrop operations on the canvas to let the user change the location of the charts and header.
You can use GridSplitter to make them user-resizable
Then, when user hits Apply, Save the canvas object using XamlWriter.Save method
When you need it for later use, load it using XamlReader.Load method
In your ViewModel have a command that gets the canvas as a parameter and handles the Save operation.
Example
view:
<Canvas x:Name="mainCanvas">
<StackPanel>
<TextBlock Text="My Header ..."/>
<!-- Charts goes here .... -->
<Button Content="Apply">
<i:Interaction.Triggers>
<i:EventTrigger EventName="Click">
<i:InvokeCommandAction Command="{Binding ApplyCommand}" CommandParameter="{Binding ElementName=mainCanvas}"/>
</i:EventTrigger>
</i:Interaction.Triggers>
</Button>
</StackPanel>
</Canvas>
view model:
public class MainWindowViewModel
{
public MainWindowViewModel()
{
ApplyCommand = new DelegateCommand<Canvas>(canvas =>
{
string userLayout = XamlWriter.Save(canvas);
// save userLayout for later use ...
});
}
public DelegateCommand<Canvas> ApplyCommand { get; set; }
}
Hope this helps
If the application specifically deals with changes in layout and layout information is the data you are presenting, then putting layout information in your view model is certainly appropriate. However, simple presentation information does not belong in your view model.
For that you need a different solution. Consider this.
If I need to locate view model template location on screen, how do I do it? My view model cannot know about the visual tree! Bugger. To solve this, I tag elements with attached properties and use a custom layout behavior or control to query the attached properties.
This is very similar to how jQuery allows a javascript programmer to grab DOM elements from a web page.
Is it possible to open another Window in a TabControl's TabItem?
The reason I want to do this is that if I have 5 TabItems in my TabControl, the one Window file I'm coding all these TabItems and their associated actions will get very large. So it would be nice if it was possible to to give each TabItem its own Window file.
Or how do you solve the problem where theWindow file controlling the TabControl gets too large?
<Window ...
xmlns:local="clr-namespace:MyNamespace"
>
<TabControl>
<TabItem Header="FirstTab">
<local:MyFirstTabUserControl/>
</TabItem>
<TabItem Header="SecondTab">
<local:MySecondTabUserControl/>
</TabItem>
<TabItem Header="ThirdTab">
<local:MyThirdTabUserControl/>
</TabItem>
</TabControl>
</Window>
Your each TabUserControl is actually simple UserControl, since TabItem can host any control as its own child.
You have several choices:
add one or more resource dictionaries to your app that contain resources with templates and styles for the various views you host in your tabs. This approach works well if you just need to maintain separation of the visual trees only.
create user controls for each view (with own XAML and class file) and use one instance for each different view in the tabs. This approach allows you to encapsulated specific business logic and the corresponding visual tree together.
generate some of the UI from code. This one has no advantages, except t makes you XAML smaller. And is your .cs files become too big, you can always split them in multiple code files and use partial classes. (just had to throw in this one for completeness :-))
You can also set the TabItem Content equals to your Window content
ex: [WindowType is your window]
WindowsType oWindow = new WindowType();
TabItem oTab = new TabItem();
oTab.Content = oWindow.Content;
Make a UserControl for each TabItem.
You can use a UserControl as was mentioned already.
But you can also use the Page control. Each "Window" would be a page, and the tab would have a NavigationControl in it. I've used this approach before and it works well. I prefer the UserControl route, but both are valid.