Suppose we have a very 'XAML long' ControlTemplate for our Control.
And we want to add just 1 Button to the Template.
MSDN claims that 'There is no way to replace only part of the visual tree of a control'.
Do I really have to copy all that ControlTemplate and add my Button to it?
Or: Is there any possibility how to provide some kind of an interface to a specific element? For example a TextBox, so that everyone could easily template it, without having to reapeat the whole ControlTemplate.
Thanks !
As qntmfred has said, you can't do this directly. However, if you own the control that you want to customise (which it sounds like you do), then you can do this by adding suitable customisation properties, such as a CustomButtons property (which each user of the control could add their own buttons to) or an ExtensionContent property (which each user of the control could set to whatever content they wanted -- leave it empty, add a single control, or add a panel with as many things as they wanted on it). Your ControlTemplate would assign no semantics to these properties, but just host them as they were given to it. For example, suppose you provided an ExtensionContent property. Your ControlTemplate could present this using a ContentPresenter:
<ContentPresenter ContentSource="ExtensionContent" />
And your users could put whatever they wanted in it:
<s:StefansControl>
<s:StefansControl.ExtensionContent>
<StackPanel Orientation="Horizontal">
<TextBlock Text="I'm custom content" />
<Button Click="DoSomethingSurprising_Click">Click me</Button>
<Image Source="something.jpg" />
</StackPanel>
</s:StefansControl.ExtensionContent>
</s:StefansControl>
Another possibly is to provide Style properties that you apply to parts of your control so that users can style them (including changing the template of that part (only) of the control) without replacing the entire style/template. This is kind of your "interface to a specific element" idea e.g. provide a FooBoxStyle property which gets applied to the "foo" TextBox.
In short, the idea is to build a certain measure of "partial replaceability" into the base template -- whether by using content, styles, templates or a combination of these. WPF doesn't provide a general notion of "partial replacement," but you can provide your own specific notion of partial replaceability provided you can predict what kind of partial replacements may be required.
MSDN is correct. Gotta copy the entire ControlTemplate.
Actually you can. It's not the most comfortable method, but here is how you do it:Cloning a WPF ControlTemplate
Related
I need to create an application that will take an .ini file which will contain
min
max
default
values for the elements, allows user to edit these values and save a new .ini file. Since .ini files can not contain different elements in the specified groups the GUI needs to be generated dynamically.
From what I have read about WPF it largely stands on data-binding and Notifying Property changes.
Since my view model needs to accommodate different numbers of variables I am not going to have the ability to bind to properties, i was planning to attach one event handler to all text boxes which will pick the corresponding validation rule when the TextBox loses focus or Enter is pressed. After that, it should update the model accordingly if it passes validation and update the View using the model for the corresponding value.
I was wondering whether this sounded like a valid idea, whether there is similar design pattern I should read about or should I just steer away from WPF altogether?
You can still use bindings - since WPF supports item templating, and since you are using an MVVM pattern you can just create a VM for each sub-item in the list (you don't even need to do this you can bind directly in the template of each list item to a DTO or business object)
I'm currently doing a similar thing now - I have a list of material tests for a client, they want to have a variable number and type of tests for each material, but also be able to tweak and change those tests per order for their customer
They actually have two test types, but to describe the simpler of the two cases (which doesn't require child VMs as such) I just created an ItemsControl that has an item template:
<ItemsControl ItemsSource="{SomeBinding}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<StackPanel>
<TextBlock Text="{PropertyDescription}" />
<TextBox Text="{PropertyValue}" />
</StackPanel>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
In this case the model just contains a list of property names/values and displays them in a stackpanel (you may need to set the ItemPanel using an ItemsPanelTemplate. Obviously you could have an extended ItemsControl that allows a DataTemplateSelector to display a different data template per type (in fact WPF already support per-type data templates).
I'm currently using Caliburn.Micro which actually does a lot of setting up child-templates for you - so if you create the bound items as a VM you can do something as simple as this:
<ItemsControl x:Name="SomeBinding" />
And CM takes care of the rest as long as the child items in the SomeBinding property are VMs themselves (though that's another story :P)
Wrap this library with a class that implements INotifyPropertyChanged so WPF can update itself once properties change. That way you can effectively databind to an INI file.
I am trying to come to a working understanding of how databinding works, but even after several tutorials I only have a basic understanding of how databinding works. Thus this question might seem fundamental to those more familiar with silverlight. Even if it is trivial, please point me to some tutorial that deals with this problem. All that I could find simply solved this via adding the data binding on a parent page.xaml (that i must not use in my case).
For the sake of this example let us assume, that we have 5 files:
starter.cs
button1.xaml + codeBehind
button2.xaml + codeBehind
The two buttons are generated in code in the starter(.cs) file, and then added to some MapLayer
button1 my_button1 = new button1();
button2 my_button1 = new button2();
someLayer.Children.Add(my_button1);
someLayer.Children.Add(my_button2);
My aim is to connect the two buttons, so that they always display the same "text" (i.e. my_button1.content==my_button2.content = true;). Thus when something changes my_button1.content this change should be propagated to the other button (two way binding).
At the moment my button1.xaml looks like this:
<Grid x:Name="LayoutRoot">
<Button x:Name="x_button1" Margin="0,0,0,0" Content="{Binding ElementName=x_button2, Path=Content}" ClickMode="Press" Click="button1_Click"/>
</Grid>
But everthing that i get out of that is a button with no content at all, it is just blank as the binding silently fails.
How could I create the databinding in the context I described? Preferably in code and not XAML ;)
Thanks in advance
The chunk of documentation you need to read is this: XAML Namescopes
Your button1 xaml has a binding looking for an element with the name "x_button2". However in a real application there can be many controls which in turn have nested controls. All of these controls have all manner of UI elements some of which may have names.
It would be impossible to get anything done if all names throughout the entire application had be unique. Yet that would need to be true if it were for your button1 to be able to hunt down the existence of another control somewhere in the visual tree outside of that which it actually knows (its own xaml).
Hence each loaded Xaml document exists in its own "namescope" and the search for other elements with other names is limited to that "namescope".
The are various solutions to this problem depending on what you real requirements are as opposed to the simplified problem in your question.
Typically you give each of your controls a DependencyProperty to which the inner button Content property binds. In "MapLayer" as call it, could then bind the propert on one of your button controls to the other.
At our work we have a controversy going on where some people want to create user controls that combine frequently used controls like a label and a text box, or a label and a image control. That is, something like this:
<StackPanel Orientation="Horizontal">
<Image Source="/Someimage/Somewhere.gif"/>
<Label>Some text, hyperlink, or other content</Label>
</StackPanel>
and use it like this
<ImageLabel
HeaderImageSource="/Someimage/Somewhere.gif"
>
Some text, hyperlink, or other content
</ImageLabel>
The question is if they are providing enough encapsulation and abstraction to merit a separate user control?
Yes, in my opinion this is sufficient to create a separate user control - if they form a logical component in your context. In the project I'm working on we do create user controls if we have grouped components like this we want to reuse.
The main benefit is that you get control of the structure and style of the component. Consider the case where you want to do a change somewhere. E.g. add a border around the image or add some style to your label. You don't want to browse the code to find all occurences of your repeated group of components. Instead - you'd like to update this one place only - namely in the custom component you've separated out.
Another advantage is if you want to bind the components to the same object. Then you can bind your ImageLabel to the object instead, and your components can bind directly to properties within this object in a nice and clean way.
Note: I'm assuming that you actually want to reuse this component and want it to be structured and styled the same way all through your application. I would never create a user control this simple for using only once.
Seems a little bit overkill to create a UserControl for three controls; I'd consider whether or not it saved me time and effort rather than encapsulation/abstraction.
I created a ComboBox subclass and added my functionality.
Now I want to expose external properties of the TextBox for example:
<a:MyComboBox SpellCheck.IsEnabled="True" TextBox.SelectedText="{Binding X}" />
Is this possible, I maybe didn't choose the wrong particular property but I guess you understand what I mean.
Is this possible?
Do I have to create all the properties individually?
This is not possible in XAML. XAML does not allow you to address sub-properties of individual members using a property path syntax like the one you describe. (Something similar is possible for certain inheritable properties such as backgrounds and font sizes, but that uses an inheritance mechanism -- affecting all contained controls -- rather than addressing a specific sub-element, and wouldn't work for TextBox.SelectedText anyway.)
So yes, you will need to declare custom properties on the MyComboBox class to surface the features of the TextBox that you need to access from outside the MyComboBox. On the plus side, this is good discipline for encapsulation: remember that a future developer might apply a custom template to your MyComboBox that doesn't include a TextBox (or the member isn't named TextBox, or the member named TextBox is actually a RichTextEditor instead of a plain TextBox...). Explicit properties ensure that MyComboBox defines clearly what behaviour and state such a template needs to respect, and lets the template decide how to implement that, rather than the author of the template being constrained always to expose a TextBox.
Trying to implement what I thought was a simple concept. I have a user control (view) bound to a view model which provides a list of data. I have added toggle buttons to the usercontrol and would like to allow the user to use these toggle buttons to switch out which template is used to show the data. All of the templates used for the data work, and they are very different from one another so it's not just simple changes to a single template. I'd like to get this as much in XAML as possible.
Here's what I have now:
Where the data appears I have <UserControl Template="{StaticResource ListSwitchingControlTemplate}" />
In that control template I have all "sub templates" - really it's just all 3 representations with their visibility set to Collapsed. Then I use a data trigger on that control template to show the currently selected view. This works, but I noticed that all 3 representations get bound - they each act like they are active (and they are I guess).
I'd rather be able to truly switch the template at run time. I tried converting the containing user control to use a ContentTemplate for itself, but that just messes up all of the binding I have elsewhere. If only UserControls could use DataTriggers I'd be ok.
Any suggestions on how to cleanly go about getting this behavior. I have an idea that I'm just missing something simple.
Thanks,
Dave
you could do it via code?
http://www.switchonthecode.com/tutorials/wpf-tutorial-how-to-use-a-datatemplateselector ???
http://social.msdn.microsoft.com/Forums/en-US/wpf/thread/4fd42590-8375-46d0-b7bc-6c217df0f0ba/
http://social.msdn.microsoft.com/Forums/en-US/wpf/thread/dbbbb5d6-ab03-49a0-9e42-686fd41e0714
One way to do this would be to use a DataTemplateSelector.
Basically, you create a class that inherits from DataTemplateSelector and override its SelectTemplate virtual function. The return value from the function is the DataTemplate you want to use and in that function you have access to the object and its properties, which you can use to decide which template to select.
There is an example on MSDN here:
http://msdn.microsoft.com/en-us/library/system.windows.controls.datatemplateselector.aspx