I am working on new WPF/MVVM project, where I see all most all controls are written for different needs, right from textbox to treeview. All are rewritten for simple need, for example, grid,stackpanel control are rewritten to add space between each item and textbox is rewritten to include label for it so that it has both label and text input are on itself.
My question : Is there any serious issue we would encounter because of this customization?
Already, I am seeing issues with aligning all controls, will i would see any more issues because of this?.
You should never create a custom or user control to add margins, a label to a TextBox, or a new ItemTemplate to a ListBox.
UserControls are for grouping frequently used combinations of controls into one reuseable control. An example may be a custom List-of-Values control that opens a dialog. This would be fine to implement as a UserControl.
Custom controls are good when a native control does not suit your needs. Say that you want to reimplement a DateTimePicker from scratch because the native one doesn't include milliseconds.
There are no serious issues as such, but you may find yourself maintaining all these controls for the next many years without there being a need to do so.
Settings Margins should be done in the View where you are using it, or on a Style in a ResourceDictionary.
This is of course only my opinion (and that of many others, I except), but if you find that the majority of your controls are 'customized' this way, you are doing it wrong.
Style and Templates rather than UserControls and custom controls.
The main issue is that you lose the ability to alter margins only in a single view. If you change your custom controls' inner paddings and margins, you will be changing all the views in your solution. If you use a style, you can always override it by defining a new style in the view, or by setting the property directly.
I need a listview with multiple buttons for scrolling. E.g.
ScrollToTop Button
ScrollUp Button
ListView
ScrollDown Button
ScrollToBottom Button
I have got the buttons working in a WPF application by using the code mentioned here. Now, I need to reuse this by making it a control(lookless?). The layout of the listview and buttons can be horizontal or vertical. Should I use custom control or user control?
Here's what I'd recommend.
Don't use any pre-composed elements. Create a behavior ScrollList, accepting two parameters - Direction and Target, Direction will be Top || Bottom, Target you list - again you can use ElementName binding.
The reason why I'd recommend this approach is the actual code required to scroll your list is tiny, while managing layouts via properties in WPF is proved to be mess an anti pattern (yes you can go ControlTemplates, but it's definitely too havy for what you're trying to do).
If behaviors are too complex just consider creating a couple of commands.
I inherited a project that uses a RadioButtonList which inherits from a ListBox. It was taken off the web (currently cannot find a link to), and contains RadioButtonList.cs (which contains six dependency properties) and RadioButtonList.xaml (which is just styles and control templates).
This control is used in over a hundred places. It causes problems because it is not a complete and professional control. Problems such as, focus issues, keyboard navigation, and so on. (See comments.)
After much research at different times over the last couple years, it seems that this control is really not necessary. All that is needed is to set the GroupName property on a group of radio-buttons. And, the only reason why a RadioButtonList control is used is to help with data-binding a list of options through the inherited ListBox.
1) Is this control really necessary? Is there a better way?
2) Is there a professional control, open-source or otherwise, that will allow me to get the benefits of data-binding without the headaches? (We use Infragistics and DevExpress, but I am not familiar with all the controls these suites offer.)
My Answers
1a) Is this control really necessary?
If you only need one list of radio buttons, then no this control is not necessary.
If your applicaton uses many lists of radio buttons, then yes this control is necessary.
If you use a list of radio buttons in different applications, then yes this control is probably necessary.
1b) Is there a better way?
I say that deriving from a ListBox, ItemsControl, or whatever then creating styles and templates is the only way to create this control; therefore, no there is no better way.
2) Is there a professional control...
Definitely, the ListBoxEdit with the RadioListBoxEditStyleSettings.
Comments Regarding Answers
All the answers indicate that creating a RadioButtonList control is not necessary. Yet, if you need more than a couple lists of radio buttons, by the time you create the styles and control templates and maybe data template, you will end up with a collection of code artifacts that can be called a radio-button-list-control. Therefore, in my opinion, a RadioButtonList is necessary.
Moreover, my understanding is a RadioButtonList was dropped in an early WPF CTP. Which I can understand, because of the limited need for such a control that can easily be created.
Comment Regarding Accepted Answer
2) Is there a professional control...
Definitely, the ListBoxEdit with the RadioListBoxEditStyleSettings.
Lastly Comment on Mike Strobel's Answer
The RadioButtonList that I have is the end-result of his answer. While I am good at creating custom-controls, I rather let third-party component makers, such as Infragistics and DevExpress, create and support a basic control like this one.
Is this control really necessary? Is there a better way?
As #lawc points out, no, it is not necessary. It may, however, be preferable, depending on what level of flexibility you desire. A reusable style is easy enough to create, but doing it "correctly" is a bit more involved than simply setting a custom ItemTemplate.
Using Styles
An ItemsControl in WPF will wrap its items in appropriate containers. Each of the selector controls in core WPF overrides the logic which determines whether an item is capable of serving as its own container, as well as the factory code which produces new item containers. A ListBox, for example, will wrap each of its items in a ListBoxItem (unless the item itself is already a ListBoxItem). The style applied to these containers can be set for the parent ItemsControl via the ItemContainerStyle property. This differs from the ItemTemplate property, which allows you to control the appearance of the item within the container. More specifically, it overrides the content template applied to the ContentPresenter within the container.
Since a RadioButton does not derive from ListBoxItem, simply setting the ItemTemplate will produce a list of RadioButton controls embedded within ListBoxItem controls, which means they will still have the same selection chrome normally associated with ListBox controls, and possibly some layout and focus oddities. This is probably not what you want.
Instead, override the ItemContainerStyle and use it to assign a custom ListBoxItem template which embeds a RadioButton. You can probably get away with not setting the GroupName property at all, which eliminates possible name collisions. Instead, just establish a two-way binding between the RadioButton.IsChecked property and the templated parent's ListBoxItem.IsSelected property.
In order to use this technique conveniently, one generally creates a Style resource (available application-wide) which can be applied to the appropriate ListBox instances, and which sets the ItemContainerStyle. Alternatively, you can make the container style available as a global resource and set that on your ListBox instances. Either way, you need to set a property.
Using a Custom Control
While WPF evangelists often recite the philosophy of preferring custom styles over custom controls, in practice this is not always convenient. You may find it more convenient to create a RadioButtonList which extends the ListBox control, and then give it a default style which automatically applies the custom style described above. This gets you out of manually assigning the list style or container style on every ListBox instance, but it's not a huge win.
But maybe you want a bit more control over the appearance of the RadioButton items. For instance, you may want to:
Adjust the margin around the "bullet" of each RadioButton item;
Adjust the vertical alignment of the bullets relative to the content;
Support both horizontal and vertical orientations;
Automatically disable the RadioButton content for items which are not selected.
Creating your own implementation, most likely derived from ListBox, allows you to add these features easily, even after you are already using your radio list across your application. This could be done with the technique above too, though it may require an attached behavior or some attached properties, in which case you end up with a somewhat fragmented design.
Third-Party Solutions
Is there a professional control, open-source or otherwise, that will allow me to get the benefits of data-binding without the headaches?
This is not an uncommon use case, and I have no doubt there are some implementations floating around. Some may be in open source frameworks, and some may be extracted from open source applications. As for third-party implementations, I do know that Actipro ships a RadioButtonList in their Shared WPF library, which is included with all of their WPF components. When last I checked, it was not available on its own. It does, however, support all of the additional features I listed above.
I can only tell you that DevExpress uses a ListBoxEdit with a RadioListBoxEditStyleSettings to represent a group of RadioButtons. Practically it is the same as your control you are using, but i think it provides better functionality and is well tested. A RadioButton is not provided by DevExpress and in my application i use the Default RadionButton-Control provided by WPF/Silverlight.
You use the RadioListBoxEdit of DevExpress as follows:
<dxe:ListBoxEdit SelectedItem={Binding CheckItem, Mode=TwoWay}>
<dxe:ListBoxEdit.StyleSettings>
<dxe:RadioListBoxEditStyleSettings />
</dxe:ListBoxEdit.StyleSettings>
</dxe:ListBoxEdit>
More information about the ListBoxEdit of DevExpress can be found here
In my opinion you don't need this control.
You can simply use .Net ListBox to achieve all your existing functionality.
Using ListBox.ItemsSource you can data bind your options collection
Specify ListBox.ItemTemplate containing the RadioButton, in this template you can data bind your view model property to RadioButton.GroupName
IMHO, a control deriving from ItemsControl would be the cleanest approach.
Then you probably would override
IsItemItsOwnContainerOverride() with return item is RadioButton;
GetContainerForItemOverride() to return a new RadioButton() for each item and
PrepareContainerForItemOverride() to set up binding of ToggleButton.IsCheckedProperty and ContentControl.ContentProperty.
While these parts are just boilerplate code, some more efforts may lie in the implementation of the keyboard behavior.
I want to create custom WPF control that has a single "child" control inside. Subclassing ContentControl or UserControl works, but has one flaw: these controls don't work in designer mode.
By "don't work" I mean this scenario: suppose I have a Canvas with my custom control in it. I want to put, say, a Button inside my control. I drag it from the toolbox, and it appears inside my control. However, XAML view shows that the new button actually belongs to Canvas, not to my control.
I can place it inside my control by manually editing XAML, but I want the designer to work too.
Interestingly, when I subclass Canvas, Grid or Panel, designer works as expected. However, these controls have many children, which is not what I need.
How can I make a single-child control that works in designer?
how about inheriting from Border? that way you could spare yourself the hassle with Designer Extensibility
I had the same problem with a content control I am writing and found an easy solution on this
StackOverflow thread.
Just implement the HitTestCore method:
protected override System.Windows.Media.HitTestResult HitTestCore(System.Windows.Media.PointHitTestParameters hitTestParameters)
{
return new PointHitTestResult(this, hitTestParameters.HitPoint);
}
I also had a similar question here.
But after digging and digging it seams that the real answer is "NO", there isn't any official way to support dragging controls straight into a custom Content-Control at Design-Time, even implementing 'HitTestCore' as Stephan's answer suggests, does not enable drag&drop at design-time for ContentControl.
For such purposes you should consider inheriting from either Grid or Panel (to allow multiple child controls), or Border (to allow single child).
I have the following components in a WPF application:
(1) Window
(2) ContentPresenter in the Window that is bound to a property in the underlying ViewModel. This Property references another ViewModel.
(3) A DataTemplate for the ViewModel that will be bound to the ContentPresenter referenced above. This data template instantiates a third-party grid that displays some data.
Whenever the ContentPresenter renders the data from the DataTemplate, it takes approximately three to four seconds for the UI to render. This causes the UI to hang for the duration of the time that it takes to render the content. Since I have little to no control over how the third-party control renders itself - my question involves whether or not it is possible to render content in a way that the UI will not hang.
Please advise.
Thanks.
Chris
How many rows is the grid displaying? And how many of those rows are visible on screen?
I'm asking because it's possible that you've got a UI layout that defeats virtualization. Usually, controls that show a scrollable list of data will perform virtualization. (The built-in ListBox does this, and any 3rd party grid of tolerable quality should do the same.) This is critical for performance, because it means your UI only needs to instantiate those items that are actually visible, rather than everything in your list.
But it's relatively easy to defeat this virtualization by accident. One way is to wrap the list or grid control in a ScrollViewer. You need virtualizing controls to be able to manage their own scrolling for virtualization to work, so the scrolling needs to happen on the inside. Wrapping a control in a ScrollViewer prevents it from doing its own scrolling. Another way it can go wrong is if you plug in a different ItemsPanel. A third possibility is that your list/grid control actually needs to be told to use virtualization.
But if you're using a control that simply takes a long time to render just the stuff you need to show on screen, then there's not much you can do - you'd need to contact the control vendor, or consider using a different vendor...