I am relatively new to WPF, but can you provide an example of how to bind a slider value to a selected item in a listbox. Ideally, as the user moves the slider, the onscreen item changes dynamically as the slider value changes. From reading, I understand that you need to use an attached property or value converter since we are binding different types of values. If so, can you provide a simple example of the most efficient method.
Thank you.
Not sure if this really is the question, but in case you mean to move the selected item through the ListBox items you could directly bind the SelectedIndex of the ListBox to the Slider Value:
<StackPanel>
<ListBox SelectedIndex="{Binding Value, ElementName=slider}">
<ListBoxItem>1</ListBoxItem>
<ListBoxItem>2</ListBoxItem>
...
<ListBoxItem>10</ListBoxItem>
</ListBox>
<Slider Name="slider" Minimum="0" Maximum="9"/>
</StackPanel>
Of course you would have to adjust the Slider's Maximum value to the actual number of items minus one.
Related
I'm new to WPF and I have this ListBox which I want to instantiate with a specific ListBoxItem, so the user knows what to do with the ListBox.
<ListBox Name="DbListBox"
Grid.Column="3"
HorizontalAlignment="Left"
Height="246"
Margin="0,99,0,0"
Grid.Row="1"
VerticalAlignment="Top"
Width="211"
SelectionMode="Single"
SelectedItem="{Binding Path=selectedDB,Mode=TwoWay}"
AllowDrop="True"
Drop="DbListBox_Drop">
<ListBoxItem Name="ListBoxItem" FontStyle="Italic">Drag .db file here or add below</ListBoxItem>
</ListBox>
Then I have some code which adds a collection of items to the ItemsSource of this ListBox, but I can't do that since the ItemsSource is not empty
DbListBox.ItemsSource = DbCollection;
My question is, how can I start up the ListBox with the item inserted first, and then when DbCollection is added to it, it simply overwrites the first ListBoxItem?
When using WPF properly, we'd normally have something like this, where a collection property would be data bound to the ListBox.ItemsSource property:
<ListBox ItemsSource="{Binding SomeCollectionProperty}" />
Once we have this XAML, we don't need to touch the ListBox again, as we can add or remove items from the data bound collection and they will magically appear (or disappear) from the ListBox:
SomeCollectionProperty.Add(new SomeDataType());
SomeCollectionProperty.Remove(someItemFromCollection);
The SomeDataType used here is up to you... it depends on what you want to display in your items. If it was just a plain string for example, then you could simply do this to add your initial item into the collection:
SomeCollectionProperty.Add("Drag .db file here or add below");
If you wanted to make that item look different to the others then you'd need to data bind a custom class that has a Text property and FontStyle property for example. You could data bind these properties in a DataTemplate to design each item to be exactly as you want it. However, that's a completely different question.
To find out more about these things, you can read the Data Binding Overview and Data Templating Overview page on MSDN.
Say I have a ComboBox which has an array of doubles as the ItemsSource. In that array are the numbers "1.0" and "2.5". If I change the SelectedValue to "3.0" the ComboBox goes blank. How do I get the ComboBox to display "3.0" without having to add it to the list of possible values that would appear in the drop-down box?
I guess what I'm really asking is do I need some sort of customised combobox to display an item that is not in the drop down list?
The simplest (but not best) way to achieve your requirements (gathered from the comments because you didn't explain them properly in your question) is to add a TextBlock in front of your ComboBox:
<Grid>
<ComboBox ItemsSource="{Binding Items}" ... />
<TextBlock Text="{Binding Output} Visibility="{Binding IsOutputVisible, Converter=
{StaticResource BooleanToVisbilityConverter}}" />
</Grid>
You could then add a bool IsOutputVisible property to make it visible or hide it whenever you need to... you'd need to use a BooleanToVisbilityConverter to make this work.
I have a combo box in a wpf c# application. In the xaml i am trying to do the following.
The ItemsSource comes from one variable.
SelectedItem sets a value on another variable
But i want the text displayed to come from a new variable.
How do i stop making the selected itemssource appear as the main text?
<ComboBox x:Name="ComboPlay" FontSize="14" MinHeight="20" Margin="0,2,4,4" Grid.Row="1" Grid.Column="3" MinWidth="160"
ItemsSource="{Binding ComboBoxList}"
SelectedItem="{Binding OutputChannel.Value, Converter={StaticResource ResourceKey=ValueToStringConverter}}" Grid.ColumnSpan="1"
IsEnabled="{Binding IsDriveChoiceEnabled}"
HorizontalContentAlignment="Center" VerticalContentAlignment="Center"/>
If you mean changing the display of the item currently selected (the portion of the control shown when the dropdown is closed), take a look at Can I use a different Template for the selected item in a WPF ComboBox than for the items in the dropdown part?
Honestly, a quick search dug up that one and many similar ones. Probably the simplest way, like the linked answer, is to figure out if your item is wrapped in a ComboBoxItem and display it differently then. Or you could re-template the ComboBox. Or you could derive from it (and re-template it) and provide a separate dependency property for the template of the selected item, if you expect to reuse it in different contexts. The sky's the limit.
I have this WinRT XAML:
<ComboBox x:Name="comboxGroupName" Grid.Row="1" Grid.Column="1" Grid.ColumnSpan="3" Margin="4" Width="200" Height="36" HorizontalAlignment="Left" ></ComboBox>
When I click in it to enter a new value, though, it seems to convert itself into a readonly textbox (it loses its down arrow and disallows any typing into it). What do I need to do to allow adding values into the comboBox? Or do I need to use a separate TextBox to do that (I reckon so, but I'd like to avoid that if reasonably possible)?
It looks like your only option will be to use a seperate TextBox. There is an IsEditable property, but it states:
Gets a value that indicates whether the user can edit text in the text box portion of the ComboBox. This property always returns false.
and the ComboBox Page states:
You populate the ComboBox by adding objects directly to the Items collection or by binding the ItemsSource property to a data source. Items added to the ComboBox are wrapped in ComboBoxItem containers.
Basically, I have a list of colors and a defined datatemplate for listbox item:
<DataTemplate x:Key="colorItemDataTemplate">
<Border x:Name="borderInner" BorderBrush="Black" BorderThickness="1" Background="{Binding Brush}" Width="11" Height="11" />
</DataTemplate>
Now, when I add a bunch of items into the listbox and then set the ListBox.ItemsSource property to my List, the listbox is filled correctly.
There is also a slider with its appropriate event handler. Within the event handler, Brush property of one of the items from the listbox is changed. Since the appearance of the item depends on the Brush Property, listbox should reflect the change.
I could reset the ItemsSource property, but then all items have their templates applied and with more than 200 items in the listbox, this is pretty slow.
So, is there any way to refresh the template for only one item from the listbox?
Thanx
I'm not sure I follow. If you've bound the Background to the property, changing the property should automatically udpate the background of the ListBoxItem. If you're not seeing that, make sure you are either using a DependencyProperty or implementing INotifyPropertyChanged.
You could use a binding converter. In the converter class you could have some logic like
(pseudo-code)
if (ListBoxItem.IsSelected)
return SpecialColorFromSlider
else
return NormalListBoxColor