I’m trying to extend an Expander’s header (the ToggleButton part) to allow for some more custom features. Being rather new to extending WPF controls using ControlTemplates, I have already accepted by now, that I will have to completely replace the Expander’s template by my own (without being able to reuse originally defined components, or even styles, which makes this quite a bit annoying in my opinion – but that’s not what the question is about).
However, I wanted to introduce some properties which change the way the component looks and works. So I created a new subtype of Expander which simply defines the new dependency properties I want to use. But I noticed that, given that I want to use those properties within the template for the ToggleButton, which is nested inside of the one for the Expander, I cannot use those properties like that. So I had to subtype ToggleButton too, define the dependency properties for that type as well, and make the Expander’s template pass the values through to the ToggleButton template.
So I ended up with two new types in the namespace (nesting the new ToggleButton type inside of the Expander subtype didn’t work?), a complete copy of the Expander’s template with only a single line changed (where the ToggleButton was inserted, passing through the new properties), and then the actual desired changes for the ToggleButton template.
And here comes the question: Is there any way to make this less complicated? To reduce the amount of work that needs to be done just for extending a subcomponent of another’s template? Or just a way to use the parent’s (Expander) properties inside of the ToggleButton template without having to subtype that one as well?
I ended up using what jberger suggested in the comments:
Using the following binding expression I did not need to duplicate the DependencyProperties into another component for the ToggleButton, but could just access the Expander’s properties inside the nested template:
{Binding CustomProperty, RelativeSource={RelativeSource
FindAncestor, AncestorType=local:CustomExpander}}
Sadly, but as expected, one apparently cannot reuse template parts from the default. However in this case I could leave out parts from the original template that I didn’t need in my copy. For example the different styles for non-default expanding (i.e. other than Top), as my expander is specialized to that layout.
This however rendered the ExpandDirection property useless, but I personally can accept that. It might lead to a follow-up question though; if one should rather build the component from scratch (based on Expander’s base, instead of Expander itself).
Related
I'm new to wpf and now I have a problem. I have a model class say Customer and I've created a DataTemplate with TargetType property set to Customer. It works good. But I actually want two different templates like one for just displaying the record and another for in-place editing. Is it possible to specify two different templates for same datatype based on some creteria?
And I want to switch this template based on some property on ViewModel like when IsEditmode is True.
Or am I doing it wrong? Should I use styles instead?
Your approach seems to be perfectly fine.
You can create a DataTemplateSelector which will allow you to choose a data template based on arbitrary criteria from code behind.
I often use these to decide which template to use based on a enum-type property.
There are two easy ways I can think of, ofcourse there are other ways based on the complexity and architecture you want to follow.
Define DataTemplate with 'Key' and specifically call that either using StaticResource/DynamicResource Binding.
You can have a DataTrigger inside the datatemplate which makes some parts of the template visible/collapsed based on your 'EditMode' property
I wanted to know which one amongst Style and UserControl would be better to use in WPF?
For example:
I have created an image button in two different ways.
One uses Style and ContentTemplate property is set.
It uses one other class with dependency properties.
The other way is I have created a UserControl which has a button and its content property is set.
The file UserControl.xaml.cs also contains the dependency properties.
For Code details see the answers of this question:
Custom button template in WPF
Which one would be better to use? In which scenario should one go for Style or UserControl or any CustomControl?
Styles are limited to setting default properties on XAML elements. For example, when I set the BorderBrush , I can specify the brush but not the width of the border. For complete freedom of a control’s appearance, use templates. To do this, create a style and specify the Template property.
Styles and templates still only allow you to change the appearance of a control. To add behavior and other features, you’ll need to create a custom control.
For example,
To create a button like a play button use styles and templates, but to create a a play button which will change its appearance after pausing it use UserControl.
For this type of thing I would go with Style, even though I'm not really adept with graphical tools. I tend to produce a basic, boring style that I can get started with and then prettify it once the application functionality has been verified.
The nicest thing about WPF is being able to distance much of the graphical look, feel and behaviour away from the code.
This allows you to change the style of your application without revisiting the code and indeed means that you can change styles on the fly at runtime.
There is an awkward line to tread with regards to how much behaviour is placed within the XAML and how much is placed within the code. A rough guide would be to decide on what behaviour must always be present within the UI and place that in the code, everything else place within the XAML.
Think of the code as being an abstract class with defined interfaces and the XAML Styles as being classes based on that class and you'll get an idea of what I mean.
Conversely, I know that people who are far more adept at the GUI work prefer to put more functionality in the XAML and others who prefer the code side, because they find the GUI work slow or difficult.
When thought of that way you'll see that there's never really a right or wrong answer, just better solutions that suit your skills.
if a style is used, it can not be modified agaign. so i need a clone method. but its hard to implement.
what i want to do is implementing a cascading 'style' mechanism. for example, i set two style to the same frameworkelement. the same property of latter style will override the former one, while the different property remain unchanged.
but if i set the style property of the frameworkelement twice directly, the 1st style will be gone. so i use the baseon property of style class to do that. but now come across another problem, the style can not be modified after it's been set to a frameworkelement.
so now i need a clone method.
Kevin,
I have written a CloneObject class which is exactly what you are looking for. Check out my code here:
"Generic class for deep clone of Silverlight and C# objects".
Jim
thanks jim. i finally discards this 'clone' idea, because it's not that easy and seems to produce some buggy problem. so i try to create a xaml resource file, and every time i need to create a instance, i just load the xaml and call the XamlReader.load.
this can bring some performance issue, but i think the cost is acceptable. and i can do styling job in blend for that specified xaml file.
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