Develop Reference

WPF/C# Label Content to ComboBox

I have a WPF/C# app with a tiny issue. I have a label that is passing the string value of AZ. I have a combobox that has AX, AY, and AZ values bound to the database. For some reason, the label value is not matching to the combobox value.
So, I have
CbCode.SelectedValue = Code;
Code is coming from another window
public SystemCode(string Code)
{
InitializeComponent();
Code = sysCode;
}
public string Code { get; }
The debugger tells me the string value is AZ, bu the combobox in the screen is the default the value of AX.
So how do I get the label content to set the page load value of the combobox?
XAML:
<ComboBox x:Name="CbCode" DataContext="{StaticResource CodeViewSource}"
SelectedValuePath="Code" ItemsSource="{Binding}" DisplayMemberPath="Code"
HorizontalAlignment="Left" Margin="106,103,0,116.4" Width="97"
d:LayoutOverrides="Height"/> <TextBox x:Name="TxtZipFive"
HorizontalAlignment="Left" Height="23" Margin="106,0,0,85.4"
TextWrapping="Wrap" Text="" VerticalAlignment="Bottom" Width="97"/>

Your question is not clear enough, but I think you need to use:
UpdateSourceTrigger=PropertyChanged

Why does my dropdown feel so clunky?

I have a XAML UserControl embedded in a WinForms/WPF Interop ElementHost control. The control is pretty simple - it's just a dropdown with a button - here's the entire markup:
<UserControl x:Class="Rubberduck.UI.FindSymbol.FindSymbolControl"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:local="clr-namespace:Rubberduck.UI.FindSymbol"
mc:Ignorable="d"
d:DesignHeight="27" d:DesignWidth="270">
<UserControl.Resources>
<local:DeclarationImageConverter x:Key="DeclarationImageConverter" />
</UserControl.Resources>
<UserControl.CommandBindings>
<CommandBinding Command="local:FindSymbolControl.GoCommand"
Executed="CommandBinding_OnExecuted"
CanExecute="CommandBinding_OnCanExecute"/>
</UserControl.CommandBindings>
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
<ColumnDefinition Width="32" />
</Grid.ColumnDefinitions>
<ComboBox IsEditable="True"
ItemsSource="{Binding MatchResults}"
SelectedItem="{Binding SelectedItem, UpdateSourceTrigger=PropertyChanged}"
Text="{Binding SearchString, UpdateSourceTrigger=PropertyChanged}"
IsTextSearchCaseSensitive="False"
IsTextSearchEnabled="True"
TextSearch.TextPath="IdentifierName">
<ComboBox.ItemTemplate>
<DataTemplate DataType="local:SearchResult">
<StackPanel Orientation="Horizontal" VerticalAlignment="Center">
<Image Height="16" Width="16" Margin="2,0,2,0" Source="{Binding Declaration, Converter={StaticResource DeclarationImageConverter}}" />
<TextBlock Margin="2,0,2,0" Text="{Binding IdentifierName}" FontWeight="Bold" MinWidth="140" />
<TextBlock Margin="2,0,2,0" Text="{Binding Location}" />
</StackPanel>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
<Button Grid.Column="1"
Command="local:FindSymbolControl.GoCommand">
<Image Height="16" Source="pack://application:,,,/Rubberduck;component/Resources/arrow.png" />
</Button>
</Grid>
</UserControl>
The problem is that it doesn't work reliably, and far from instinctively.
If I type something in the box that actually matches an item, nothing happens until I manually select that item in the dropdown. Like here, I typed "sleepD", the box autocompleted to "sleepDelay", but the command is still disabled:
Once I've selected the item in the dropdown, the command button gets enabled as expected (although the image on the button doesn't show up grayed-out when the button is disabled, so it's not exactly as obvious as I intended it to be).
(the screenshot isn't really showing it, but there's only 1 match for that search)
If I click the button at that point, it works as expected. The problem is that if I make a new selection from the dropdown after that, the text box gets cleared instead of displaying the item I selected, and there's a weird delay during which the box is displaying what appears to be selected whitespace - this only seems to happen when the previous selection was made after selecting a value in the dropdown while the search text matches multiple entries, like "Sleep" above.
After the box got cleared, I can make a new selection from the dropdown and it will work as expected (except the VBE won't actually activate the CodePane I'm setting the selection to, but that's a separate issue).
The command implementation simply raises a Navigate event that passes a Declaration to the code that owns the VM instance.
The Search method, for which I need to add a .Take(50) after the .Select, to limit the number of returned results and perhaps reduce the lag a bit:
private void Search(string value)
{
var lower = value.ToLowerInvariant();
var results = _declarations.Where(
declaration => declaration.IdentifierName.ToLowerInvariant().Contains(lower))
.OrderBy(declaration => declaration.IdentifierName.ToLowerInvariant())
.Select(declaration => new SearchResult(declaration));
MatchResults = new ObservableCollection<SearchResult>(results);
}
private string _searchString;
public string SearchString
{
get { return _searchString; }
set
{
_searchString = value;
Search(value);
}
}
private SearchResult _selectedItem;
public SearchResult SelectedItem
{
get { return _selectedItem; }
set
{
_selectedItem = value;
OnPropertyChanged();
}
}
private ObservableCollection<SearchResult> _matchResults;
public ObservableCollection<SearchResult> MatchResults
{
get { return _matchResults; }
set { _matchResults = value; OnPropertyChanged(); }
}
}
There's also an IValueConverter involved, that takes the Declaration in the SearchResult and switches on the declaration's DeclarationType enum to return a pack uri that points to the .png image to use in the dropdown list.

Aaah found it. It was all in the XAML.
Right here:
Text="{Binding SearchString, UpdateSourceTrigger=PropertyChanged}"
That line doesn't belong there; binding the TextSearch.Text property instead...
TextSearch.Text="{Binding SearchString, Mode=OneWayToSource, UpdateSourceTrigger=PropertyChanged}"
Makes it all work as intended. No glitch, no lag. Well there is a lag when I first drop the dropdown, but that's another issue.
Lesson learned: when TextSearch is enabled on an editable combobox, don't bind the Text property, unless you want weird behavior.

change groupbox header text via code wpf

I would like to change the label text of a group box outside the designer. I tried the content property but it it does not works. Any help ?

Create a label inside the design like this :
<GroupBox Height="608" Margin="0,0,0,0" Width="375" x:Name="grp1">
<GroupBox.Header>
<Label Foreground="Blue" x:Name="lblGroupHeader"></Label>
</GroupBox.Header>
</GroupBox>
then In code :
lblGroupHeader.Content = "The Name"

Change AppBar's menu text

I have the following AppBar.
<Page.BottomAppBar>
<AppBar x:Name="bottomAppBar" Padding="10,0,10,0">
<Grid>
<StackPanel Orientation="Horizontal" HorizontalAlignment="Right">
<Button x:Name="switchMeasurementMode" AutomationProperties.Name = "Breath rate" Style="{StaticResource AppBarButtonStyle}" Click="switchMeasurementMode_Click" />
</StackPanel>
</Grid>
</AppBar>
</Page.BottomAppBar>
It looks like this
I tend to change its text during run-time with the following C# code
private void switchMeasurementMode_Click(object sender, RoutedEventArgs e)
{
this.switchMeasurementMode.Name = "111";
}
But the button text is not changed. Is there anything I had missed out?

If you use the default styles for AppBar in Windows 8 C# projects, then you have to change the attached property AutomationProperties.Name either in XAML using:
AutomationProperties.Name = "new name"
or in code using:
Button.SetValue(AutomationProperties.NameProperty, "new value");
or
AutomationProperties.SetName(Button, "new value");

The button is a content control. You set the Content property to change the content.
this.switchMeasurementMode.Content= "111";
The Name property is how you set the programmatic "handle" for the Button. You use the name in the code editor to modify the control. In your case, you are changing the name, which means you loose the ability to say this.switchMeasurementMode...
FYI, content can be more than just text. Most XAML elements can be added as content.

WPF: Cannot set properties on property elements weirdness

private TextBlock _caption = new TextBlock();
public TextBlock Caption
{
get { return _caption; }
set { _caption = value; }
}
<l:CustomPanel>
<l:CustomPanel.Caption Text="Caption text" FontSize="18" Foreground="White" />
</l:CustomPanel>
Gives me the following error:
Cannot set properties on property elements.
If I use:
<l:CustomPanel>
<l:CustomPanel.Caption>
<TextBlock Text="Caption text" FontSize="18" Foreground="White" />
</l:CustomPanel.Caption>
</l:CustomPanel>
My TextBlock shows up fine but it's nested inside another TextBlock like so, it even seems to add itself outside of the Caption property:
<l:CustomPanel>
<l:CustomPanel.Caption>
<TextBlock>
<InlineUIContainer>
<TextBlock Text="Caption text" FontSize="18" Foreground="White" />
</InlineUIContainer>
</TextBlock>
</l:CustomPanel.Caption>
<TextBlock>
<InlineUIContainer>
<TextBlock Text="Caption text" FontSize="18" Foreground="White" />
</InlineUIContainer>
</TextBlock>
</l:CustomPanel>
As you might have already guessed, what i'd like my code to do is to set my Caption property from XAML on a custom panel, if this is possible.
I've also tried the same code with a DependencyProperty to no avail.
So, anyone that can help me with this problem?

I can explain what is going wrong and how to fix it.
First,
<l:CustomPanel>
<l:CustomPanel.Caption Text="Caption text" FontSize="18" Foreground="White" />
is a simple syntax error. The <l:CustomPanel.Caption> syntax does not accept XML attributes - the property value must be within the element.
This is proper property element syntax:
<l:CustomPanel>
<l:CustomPanel.Caption>
<TextBlock Text="Caption text" FontSize="18" Foreground="White" />
</l:CustomPanel.Caption>
</l:CustomPanel>
but:
Property element syntax works only with DependencyProperties (so it didn't work with your CLR property) and
Property element syntax always honors the ContentPropertyAttribute of the property type
Since TextBlock has a [ContentPropertyAttribute("Inlines")], the property element syntax is trying to add the TextBlock to the Inlines collection.
The solution is simple: Declare your property as a DependencyProperty of type UIElement instead of type TextBlock. This has the additional advantage of not restricting the display of content to just a TextBlock. If you really do want to restrict it to just a TextBlock, you can use a validation callback.
public UIElement Content { get { ...
public static readonly DependencyProperty ContentProperty = ...

Just got a non-ideal workaround from a colleague of mine. It involves declaring the Caption property as a resource like:
<Page.Resources>
<TextBlock x:Key="test" Text="Caption text" FontSize="18" Foreground="White" />
</Page.Resources>
<l:CustomPanel Caption="{StaticResource test}" />
I'd still like to know why I can't use the two previous options, so if anyone knows please answer. :)

It seems that you can get this error (in Silverlight 4 and 5 at least) if you specify a namespace on the element. For example:
<Path>
<MapLayer.Position xmlns="clr-namespace:Microsoft.Maps.MapControl">
...
In this case MapLayer.Position is an attached property. It seems that the Silverlight parser requires the namespace to be defined using a prefix:
<Path xmlns:map="clr-namespace:Microsoft.Maps.MapControl">
<map:MapLayer.Position>
...