Sorry for the title, I just don't know how to explain it in one sentence.
So here is my goal: I need to have a boolean in my ViewModel define the visibility for a control (border).
I know I can achieve this with a BooleanToVisibilityConverter, but there is a little more to it. I want a button on my UI to be shown if the control is not visible. Once that button is pushed, then I want the boolean in my ViewModel to be TRUE and then I want the control to be visible and the button that was just pushed to be collapsed. Once that control is visible, I would like a button within that recently visible control to make the control collapsed and then make the original button visible.
Basically, there are two buttons: 1 to make visible (then collapse itself) and the other is to collapse its container and then make the first button visible.
I am trying to do all this with MVVM so if I can avoid code behind in my View that would be ideal!
Since you're using ICommands on your viewmodel, this should work...Assume your commands are "ShowBorderCommand" and "HideBorderCommand" and the property on your viewmodel is "ShowBorder"
<ConverterNamespace:BooleanToVisibilityConverter x:Key="BoolToVis"/>
<ConverterNamespace:ReverseBooleanToVisibilityConverter x:Key="BoolToCollapse"/>
<Border Visibility="{Binding ShowBorder, Converter={StaticResource BoolToVis}}">
<Button Command="{Binding HideBorderCommand}"/>
</Border>
<Button Command="{Binding ShowBorderCommand}" Visbility="{Binding ShowBorder, Converter={StaticResource BoolToCollapse}}"/>
My WPF Converters library has a BooleanToVisibilityConverter that allows reverse conversions, as well as allowing the use of Hidden instead of Collapsed:
<con:BooleanToVisibilityConverter x:Key="ReverseBooleanToVisibilityConverter" IsReversed="True"/>
<Button Visibility="{Binding SomeProperty, Converter={StaticResource ReverseBooleanToVisibilityConverter}}"/>
Related
I have a combobox that displays a list of items, and I want to place a button next to it which triggers a command to see the details of the selected item. So far, so good. Now I want the button to be visible only if the combobox has focus (or is in "edit" mode, but not only when the popup is open).
I thought I could bind the visibility of the button to some focus property of the combobox, something like this:
<Button Content="Details" Visibility="{Binding ElementName=elementListComboBox,
Path=IsFocused, Converter={StaticResource Bool2VisibilityConverter}}"/>
But I found no way to know if the control I want is focused or not. I looked at the FocusManager.FocusedElement, but I don't know how to get the focused control I want inside the binding. Is there a way to achieve this in XAML?
Ok, the way to get this working as I wanted is this:
<Button Command="{Binding SomeCommand}"
Content="Details"
Focusable="False"
Visibility="{Binding ElementName=elementListComboBox,
Path=IsKeyboardFocusWithin,
Converter={StaticResource Bool2VisibilityConverter}}"/>
Two key factors here: bind the button's visibility to IsKeyboardFocusWithin property of the combobox, and set the button's Focusable property to false, else it will get collapsed when you want to click on it.
Hope this is useful.
I have a WPF/MVVM app with a ListBox which displays data through a DataTemplate. I managed to change the selected item in the ListBox when pressing a button so the CommandParameter is linked to the ListBox's SelectedItem, but I cannot get the buttons to be enabled/disabled correctly in the same way. For example, if I have 2 items and the button should be enabled in one and disabled in the other, when I select an element BOTH buttons have the same state, and they BOTH change state when I select another item.
I am using a RelayCommand as used in many MVVM Frameworks.
Here is my XAML (removed "not interesting" parts):
<UserControl.Resources>
<DataTemplate x:Key="ItemTemplate">
<Grid>
<Button Content="Something" Name="EnabledDisabledButton" Click="Button_Click"
Command="{Binding RelativeSource={RelativeSource AncestorType={x:Type UserControl}}, Path=DataContext.SomeCommand}"
CommandParameter="{Binding RelativeSource={RelativeSource AncestorType={x:Type ListBox}}, Path=SelectedItem}"/>
</Grid>
</DataTemplate>
<Style TargetType="{x:Type ListBoxItem}" x:Key="ContainerStyle">
<Setter Property="ContentTemplate" Value="{StaticResource ItemTemplate}" />
</Style>
</UserControl.Resources>
<ListBox x:Name="myListBox" ItemsSource="{Binding ElementList}"
IsSynchronizedWithCurrentItem="True" ItemContainerStyle="{StaticResource ContainerStyle}"/>
I tried to pass the SelectedItem as a parameter to the RelayCommand's CanExecute method, but the result was the same as before.
Is there a way to pass the actual ListBoxItem in which the button "lives in" as a parameter to the command, so each one will be processed separately by the CanExecute method? Would it work if I got this? (right now I am handling the Click event to select the correct item in the list before executing the command).
In my CanExecute method I am evaluating some property of the SelectedItem in order to enable/disable the corresponding button. An alternative would be to evaluate this property for all elements, but I cannot think of a way to do it inside the ViewModel, and then communicate to the view the result (if it is even possible while using a DataTemplate for the items).
Thanks for your input, regards!
Converting My comment into an answer:
Why not just CommandParameter="{Binding}"?
You mention "MVVM" in the question, but it seems you use the MVVM way to your full advantage.
I would not have a Button_Click event in the style at all. That is because it is in fact a style, which per definition could be changed to another style which does not have the same event, which again will make the application stop working as wanted if you choose to have a style-based app in the future.
A rule I use is that a style is a style. A style has to do with the UI and "looks" of the app.
Functionality should be separate from the UI. The programmer can define the Command, and the designer can decide how the user will use that in the best way.
That's exactly where the code separation from the MVVM pattern cames into grip.
To separate the "looks" and user behavior and the app's logic.
Like...it should not matter to the model if a command fires from a button, a menu, a datacontext or a key stroke.
If this particular problem was handled to ME, I would solve it by having a HOLDER-class.
This is a class (DependencyObject which implements INotifyPropertyChanged) that holds a ICommand property as well as the "row" that will be displayed in the various rows in the ListBox.
The ICommand property will be bound to the Button, having the row (class) itself as CommandParameter to the call.
Then the actual row would be used in the ItemTemplate on the ListBox, with Bindings to different elements (proprty with or withouy Converters) to make whatever desired display available.
I hope I explained good enough...
Feel free to ask more if you want more details to my solution alternative.
I am using WPF split button which is inherited from
xmlns:extToolkit="http://schemas.microsoft.com/winfx/2006/xaml/presentation/toolkit/extended"
The issue is I want to disable , the button ' the one below(Right side of Button 'Conf' in below 'downarrow present in the below fig) , If user clicks on Left side of the button the rightside should be disabled and the button(leftside) background should change to yellow.please find below the xaml , I am using the wpf split button , dropdown content in this case .please let me know if you have any idea
<extToolkit:SplitButton x:Name="ABCbutton"
VerticalAlignment="Center"
Command="{Binding ACommand}"
FontSize="16>
<TextBlock HorizontalAlignment="Center"
IsEnabled="{Binding IsEnabled, ElementName=AButton}"
Text="A"/>
<extToolkit:SplitButton.DropDownContent>
<StackPanel>
<Button Command="{Binding BCommand}"
Padding="3"
Style="{DynamicResource
DropDownButtonMenuButton}">
<TextBlock Margin="0,3,6,3"
Text="B"/>
</Button>
<Button Command="{Binding BCommand}"
Padding="3"
Style="{DynamicResource
DropDownButtonMenuButton}">
<TextBlock Margin="0,3,6,3"
HorizontalAlignment="Stretch"
Text="C"/>
</Button>
</StackPanel>
</extToolkit:SplitButton.DropDownContent>
</extToolkit:SplitButton>
In a case like this, you will likely be better off creating your own control. The split button can't really handle what you are talking about without a good deal of modification.
Essentially your new control will consist of two buttons, visually styled so that they look like they blend together. Each will have it's own background and enabled property. Add a ViewModel to help control behaviors and set properties, and I think you would be in business. Keep in mind that all of the controls that are supplied in any of the toolkits, frameworks, control packs, etc are made with the primitive types of drawing and framework elements (line, rectangle, border, content presenter, panel, etc) with specialized behavior code.
I end up making a lot of custom controls just because there is not one that perfectly replicates what I want.
I have a list on my WPF xaml which contains two items. Below is the Style template for each item. Now on UI this shows like a group of radio buttons(No. of radio buttons depends on no. of items in my list).
<Style x:Key="RadioButtonListBoxItemStyle" TargetType="{x:Type ListBoxItem}" >
<Setter Property="Template">
<Setter.Value>
<ControlTemplate>
<RadioButton FlowDirection="LeftToRight"
Margin="10 15"
Content="{Binding Value}"
GroupName="{Binding DisplayGroupName}"
IsChecked="{Binding IsSelected, Mode=TwoWay}" />
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
Now I bind a list(having 2 items) using the above style template to get two radio buttons. What happens is everything works pretty fine i.e when I change the selection of radio button on UI the IsSelected property is getting updated properly to true or false depending on whether my radio is checked/un-checked. But if I try to set the list in the code manually, then from that point my binding of the radio button's with my list is lost and nothing happen's.
Any help on this would be great and based on my needs I have to set the list in the code manually. So is there any solution in a way that binding will not be lost even though I set the list in my code manually. Thanks.
-Ady.
This is a common problem with radio buttons in WPF, and it has to do an unusual aspect of binding, one that is marginally more feature than bug.
The design of binding assumes that the only two things that change the value of a binding's target property are a) actions in the UI and b) changes to the source property. If you set the target property of a binding in code - like, you explicitly set the Background of a Border, even though it has a binding - the binding decides that you know what you're doing, and that it should just get out of the way. So it turns itself off.
This is a pretty sensible design decision, for the most part. It's better than throwing an exception, for instance. Most of the time, you're not going to ever set IsEnabled in code anyway; you'll let the binding do it. Especially if you're using MVVM.
Okay, so what happens if you have radio buttons in a group?
When you check one button in the group, the WPF code that manages radio button groups unchecks all the other buttons in the group, by setting IsChecked to false in code. The binding disables itself. Oops.
Here's the solution: If you're using radio buttons and binding, don't use groups. Handle the mutual exclusion logic in your view model code. In your case, code your view models so that only one object in a collection can have IsSelected true at any given time. (Yes, this is a pain.)
The radio buttons will still work as expected, but since the only properties being set by code are the source properties, binding won't break.
you are setting the style for the listboxitem class, including the bindings. so, when you set the list from code behind it does not contain listboxitems, it contains the items from your list. so, the style does not apply. what you should do is make the <DataTemplate> for the type of item in your list--in effect telling WPF what you want each item to look like.
<DataTemplate TargetType="{x:Type MyCustomClass}" >
<DataTemplate>
<StackPanel Orientation="Horizontal">
<CheckBox IsChecked="{Binding Deleteable, Mode=TwoWay}" />
<Label Content="{Binding Name}" />
</StackPanel>
</DataTemplate>
</DataTemplate>
(this is off the top of my head, so the xaml might not be exactly right)
Given the following bit of XAML
<Border Name="Brder" Visibility="Visible" Width="10" Height="10" Background="Red"></Border>
<Button Content="Hide"></Button>
How can I set the button click to change the visibility of the border (not using code behind)?
I know it's trivial in code behind and the routed click event only seems to allow storyboard manipulation?
Thanks
If you change the Button to a ToggleButton you can bind visibility to IsChecked of the ToggleButton using XAML only. Also remember that Expanders support this behavior as well and you can laways style them if you don't like the default look.