In a DataTemplate I want to show the Control which is actually replaced by the DataTemplate. With error validation, this is possible by using <AdornedElementPlaceHolder />. However, this seems not to work in a normal DataTemplate.
I think there would be a simple solution, but just can't find it.
Thanks a lot
This is not possible and here is why. DataTemplate doesn't replace anything. Instead, a control that defines a DataTemplate contains the content provided by it. If it was possible then there would be an infinite loop (control -> data template -> control -> data template -> ...).
I suggest you read the following article to fully understand data templates: http://msdn.microsoft.com/en-us/library/ms742521.aspx
A DataTemplate in some sense "replaces" a data object and not a UI object - in other words, not a Control. If you are trying to work with properties of the Control (usually either a ContentControl or ItemsControl) that is using the template, try a RelativeSource Binding where the AncestorType is the type of the Control.
Related
I was trying to get the text that I wrote in a DataGrid cell after editing it, so I put a breakpoint in the function CellEditEnding and looked at the EventArgs and noticed that it contains the property "Text", so I wouldn't have to do the usual XAML binding hacks to get it.
However, I quickly noticed that it will not let me access it.
After taking a look at the FrameworkElement class, I can confirm that there is no Text property, so what is going on, why can't I acces the property?
why can't I acces the property?
Because a FrameworkElement indeed has no Text property.
TextBox, which derives from FrameworkElement, has a Text property though so you could cast the EditingElement to a TextBox and then access the property:
string text = (e.EditingElement as TextBox)?.Text;
Visual Studio displays the properties of the actual object in memory.
It's a bad idea to use the UI as a data store and try and directly work with it.
You should bind an observablecollection of t to the itemssource of your datagrid and work with each instance of t.
That will be far easier to work with.
As to why are some properties inaccessible?
It's because those properties aren't where you think they are. The DatagridCell has a series of things nested within it.
DataGridCell > Border > ContentPresenter > TextBlock
Download snoop https://github.com/snoopwpf/snoopwpf or install using chocolatey / your preferred method.
Run snoop.
Run your app.
Drag the right gunsight thing over you window.
A window should open up with two panels. Controls and properties.
Mouse over a datagrid cell.
press shift+ctrl and you should see the element under the mouse selected in the ui tree.
A datagrid is pretty complicated and there are multiple things in each row.
See that textblock there?
That's the thing has a text property.
Or at least that's the thing when you're not in edit mode.
Switch to edit mode and I have a TextBoxView.
So one complication is, which are you working with at a given time?
Is there a possibility to prevent a Expander control in WPF to collapse, when certain conditions are given. For my usecase it is not possible to do it directly in the xaml, because whether the Expander can be collapsed or not depends on condition just known during run time.
Its no option for me to use an event, because the project is a test project to seperate gui and code strictly.
Perhaps you can bind to the IsExpanded property.
For example you can use a DataTrigger, MultiDataTrigger, ValueConverter, or MultiValueConverter to manage the data binding to the IsExpanded property.
There's also a interesting article here that may help you.
If you want to set the Expander to always remain toggle-on. Just leaving it here.
<Expander IsExpanded="True"></Expander>
i'm using an ItemsControl to generate a list of controls based on my model.
When looking at the visual tree, i noticed that each of the rendered control is wrapped in a ContentPresenter. The controls that are added are a 3rd party control and are designed to display a splitter between each control if they are siblings..this allows a user to size each control. For example the following will show a splitter between each of the controls at run time.
<StackPanel>
<3rdPartyControl />
<3rdPartyControl />
<3rdPartyControl />
</StackPanel>
When using an ItemsControl, each of the 3rdPartyControl are wrapped in a ContentPresenter, and thus no splitter is shown. I have tried various ways to try and solve this problem but unable to get this to work unless i write code behind to add each control rather than rely on Xaml.
Does anyone know of a way to replace the contentpresenter completely (in my case with 3rdpartyControl)?
Thanks
In order to replace the ContentPresenter you could derive from ItemsControl and override the GetContainerForItemOverride method to create a specialized container control.
ListBox for example overrides this method to create a ListBoxItem as container for a new item object.
That's true, every element that you add to ItemsControl is wrapped with ContentPresenter, you can find more details about it in the greate series of articles from dr.wpf ItemsControl a-z
One way I would suggest to try is to change ItemsControl to ListBox and make ListBox act like ItemsControl. In this case you can re-style/re-template ListBoxItem and replace ContentPresenter with your control. You would also need to stop selection support. Here is ListBox style that you need to change.
I have created a data template for a data class. The width of the grid created by the datatemplate is bound to a property in the data class, ie, the size of the control matters.
I am creating a list of the data class objects, and adding them to an items control in MainWindow.
Update:
I would like to line up the controls from the data list one after another, and not have them resize.
Example:
[---------box1----------][--box2--][------box3-----]
each are the same data template type, and different widths. Perhaps I shouldn't be using itemsControl, but I am unsure of what other control to use to achieve this.
Any help would be much appreciated. I can post XAML
Can you post some XAML.
It can depend on the HorizontalContentAlignment of the ItemsControl or the style of your ItemContainer/ItemPanel.
I've got an ObservableCollection of POCOs (Plain old CLR Objects) that I want to represent in a tabbed idiom. Prefereably using the MVVM pattern, is there a way to bind the collection of TabItems to the count of my POCO collection?
So, in this case if there are 3 items in my collection, I'd like to see 3 TabItems. Each TabItem would contain the same controls in the same location, each control bound to properties of the appropriate object in the collection.
I'm just looking for an overview of the approach I might use or a link to an example. If you need more info, feel free to ask.
Thanks.
I'd probably create an ObservableColletion with your POCO items in it. You could then bind that ObservableCollection to any of the Silverlight Item Rendering controls. You'll have to modify the default rendering template to create your tabs...but using that method, your tabs will constantly be up to date with the items in the collection without having to put any code in the code behind file.
UPDATE
Here's a link to the Silverlight Forums where somebody built a TabControl using the ItemsControl with sample XAML code:
http://silverlight.net/forums/t/12271.aspx
...just scroll down a bit to see the sample.
One way to do this is to use a value converter (IValueConverter) to return your POCO wrapped in a TabItem. I posted an example here as part of a related question. There is also sample xaml binding and injection of the ViewModel as a parameter to the value converter.
/jhd