Develop Reference

How to modify Image Source in WPF XAML dynamically

I have a WPF App that has (so far) 2 modes of display, regularmode and widgetmode.
I am using Prism 6 with MVVM design pattern.
MainWindowViewModel knows the mode of display.
ToolBarView has, as expected, a toolbar of buttons and the buttons shall be dynamically changed to different images depending on the mode of the view. If the mode is WidgetMode, it switches to the image with an identical name but with an '_w' added. So instead of "image.png", it's "image_w.png".
What I'd like to do is create a string in ToolBarView that is updated to either String.Empty or to "_w", depending on the mode. I'd also like the image root folder to be a global string, rather than a hardcoded string, so I have defined that in app.xaml.
<Application.Resources>
<sys:String x:Key="ImageURIRoot">/MyApp;component/media/images/</sys:String>
</Application.Resources>
Then in my toolbarview (a usercontrol), I did this:
<UserControl.Resources>
<converters:StringToSourceConverter x:Key="strToSrcConvert"/>
<sys:String x:Key="BtnImgSuffix">_w</sys:String>
.
.
.
</UserControl.Resources>
Note that the string is hardcoded; eventually, I will change it dynamically based off the windowmode.
I then put the Buttons in a Listbox
<ListBoxItem Style="{StaticResource MainButton_Container}">
<Button Command="{Binding ButtonActionDelegateCommand}" Style="{StaticResource Main_Button}">
<Image Source="{Binding Source={StaticResource ImageURIRoot}, Converter={StaticResource strToSrcConvert}, ConverterParameter='{}{0}button.png'}" />
</Button>
</ListBoxItem>
Converter code:
public class StringToSourceConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if (parameter is string)
{
return string.Format(parameter.ToString(), value);
}
return null;
}
public object ConvertBack(object value, Type targetTypes, object parameter, System.Globalization.CultureInfo culture)
{
return null;
}
}
So that works. But what I want is to have the ConverterParameter equal "{}{0}button{1}.png", where {0} is the URI Root and {1} is the suffix. But I can't figure out how to do it. I know it's simple, but I can't put my finger on it!
Please help!

Figured it out and it was through multibinding. The way I did it was create a converter that inherits from IMultiValueConverter. Its "Convert" method looks like this:
public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
{
ImageSourceConverter conv = new ImageSourceConverter();
int suffixPos = ((String)parameter).Length - 4;
var returnValue = ((String)parameter).Insert(suffixPos, values[1].ToString());
returnValue = Path.Combine(values[0].ToString(), returnValue);
ImageSource imgsrc = conv.ConvertFromString(returnValue) as ImageSource;
return imgsrc;
}
The xaml looks like this:
<Image Height="30" Width="40" diag:PresentationTraceSources.TraceLevel="High">
<Image.Source>
<MultiBinding Converter="{StaticResource stringsToSrcConvert}" ConverterParameter="buttonImg.png">
<Binding Source="{StaticResource ImageURIRoot}"/>
<Binding Source="{StaticResource BtnImgSuffix}"/>
</MultiBinding>
</Image.Source>
</Image>
Also, had to modify the URIRoot
<Application.Resources>
<sys:String x:Key="ImageURIRoot">pack://application:,,,/MyApp;component/media/images/</sys:String>
</Application.Resources>
Thanks, Clemens!

Windows Phone update/refresh binding

I have a textblock in my listbox called "feedTitle" which I want to change the forground color of. I use Foreground="{Binding Converter={StaticResource NewsTextColorConverter}}" for the binding of the forground color. Now the strange problem is that, if I choose a color in the listpicker("Lys" or "Dark" value) it runs the IValueConverter Convert method, but it dont show the color in the GUI, only if I restart my whole app it shows the color I chosen. It's like it only set the color of the forground of the textblock once.
MainPage.xaml
<ListBox Grid.Row="1" Name="feedListBox" ScrollViewer.VerticalScrollBarVisibility="Auto" SelectionChanged="feedListBox_SelectionChanged">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel VerticalAlignment="Top">
<TextBlock TextDecorations="Underline" FontSize="24" Name="feedTitle" TextWrapping="Wrap" Margin="12,0,0,0" Foreground="{Binding Converter={StaticResource NewsTextColorConverter}}" Text="{Binding Title.Text, Converter={StaticResource RssTextTrimmer}}" />
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
And in my app file:
App.xaml
<Application.Resources>
<converter:NewsTextColorConverter xmlns:converter="clr-namespace:NordjyskeRss" x:Key="NewsTextColorConverter" />
</Application.Resources>
I use a listpicker where a user select the value "Mørk" or "Lys" and then I want the textblock forground color to update its forground color. I call the Convert method and pass null as arguments, it seems to run the method fine:
MainPage.cs
private void lpkThemes_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
// Make sure we don't handle the event during initiation.
if (e.RemovedItems != null && e.RemovedItems.Count > 0)
{
if (this.lpkThemes.SelectedItem != null)
{
settings[THEMES_SETTING_KEY] = lpkThemes.SelectedItem.ToString();
if (lpkThemes.SelectedItem.ToString() == "Mørk")
{
n.Convert(null, null, null, null);
}
else
{
n.Convert(null, null, null, null);
}
}
}
}
This is where I use a IValueConverter to check for what color to use on the textblock and then add it:
MainPage.cs
public class NewsTextColorConverter : IValueConverter
{
protected IsolatedStorageSettings settings = IsolatedStorageSettings.ApplicationSettings;
protected const string THEMES_SETTING_KEY = "Themes";
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
if (settings.Contains(THEMES_SETTING_KEY))
{
string themesValue = (string)settings[THEMES_SETTING_KEY];
if (themesValue == "Mørk")
{
return new SolidColorBrush(Colors.Green);
}
else
{
return new SolidColorBrush(Colors.Blue);
}
}
return new SolidColorBrush(Colors.Green);
//throw new NotSupportedException("ColorToBurshConverter only supports converting from Color and String");
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
throw new NotImplementedException();
}
}

I think you need to redesign your app in the following way:
Add the following line into your app.xaml or page resources: <SolidColorBrush x:Key="brushListItemsForeground" Color="#FFFFFFFF" />
Replace Foreground="{Binding Converter={StaticResource NewsTextColorConverter}}" with Foreground="{StaticResource brushListItemsForeground}"
In your SelectionChanged:
var brush = (SolidColorBrush)Application.Current.Resources["brushListItemsForeground"]; if you’ve added the brush to app.xaml, or = (SolidColorBrush)this.Resources["brushListItemsForeground"]; if you’ve added the brush to page resources. Then change the Color property of the brush based on your settings.
P.S. There’re also other correct ways: e.g. create a SettingsContainer class that implements INotifyPropertyChanged, add it into some resource dictionary <local:SettingsContainer x:Key="mySettings" />, then bind to its properties e.g. Foreground="{Binding listItemsForeground, Source={StaticResource mySettings}}", when you need to change the value, change the listItemsForeground property of your class and raise PropertyChanged.
Currently, you’re abusing value converter using then as value providers, they were not designed for that, and that is why you have issues updating those values.

Setting Image in ListView based on criteria

I'm doing a budgeting module.
I will like to ask that how to set the GridViewColumn to display out my desired image based on the value which I retrieve from database which are "income" & "expenses". I know how to retrieve the value from the database & display in the lisview but my question for today is that I will like to have some condition which is when found "income" will populate with income image then found expense will populate with another image???
Can this be possible. Hope to receive reply as soon as possible. Thank you.
I will provide my codes for better refer:
XAML file:
<DataTemplate x:Key="CategoriesType">
<Border BorderBrush="#FF000000" BorderThickness="1,1,0,1" Margin="-6,-2,-6,-2">
<StackPanel Margin="6,2,6,2">
<TextBlock Text="{Binding Path=CategoriesType}"/>
</StackPanel>
</Border>
</DataTemplate>
<Style x:Key="MyItemContainerStyle" TargetType="{x:Type ListViewItem}">
<Setter Property="HorizontalContentAlignment" Value="Stretch" />
<Setter Property="VerticalContentAlignment" Value="Stretch" />
<!--<EventSetter Event="PreviewMouseLeftButtonDown" Handler="ListViewItem_PreviewMouseLeftButtonDown" />-->
</Style>
</Window.Resources>
<ListView Height="320" HorizontalAlignment="Left" Margin="12,154,0,0" Name="CategoriesListView" VerticalAlignment="Top" Width="316" ItemsSource="{Binding}" ItemContainerStyle="{DynamicResource MyItemContainerStyle}">
<ListView.View>
<GridView>
<GridViewColumn Header="Types" Width="40" CellTemplate="{DynamicResource CategoriesType}"/>
</GridView>
</ListView.View>
</ListView>

Add an image tag in the tamplate and use a converter to return the correct image based on the string value (untested code)
xaml:
<UserControl.Resources>
<Converters:TypeToImageConverter x:Key="typeToImageConverter" />
</UserControl.Resources>
<StackPanel Margin="6,2,6,2">
<Image Source="{Binding Path=CategoriesType,Converter={StaticResource typeToImageConverter}"/>
<TextBlock Text="{Binding Path=CategoriesType}"/>
</StackPanel>
TypeToImageConverter.cs:
public class TypeToImageConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
if (value == null)
throw ...
var str = value.ToString();
if (str == "income")
return new BitmapImage(...);
if (str = "expenses")
return new BitmapImage(...);
return null;
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
throw new NotImplementedException();
}
}

I found the solution for my answer which is the format of the string. Which causing me to unavailable to retrieve the image with few hours of troubleshooting & debugging. I finally found out the solution :)
I solve it by like this:In my converter.cs
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) {
string str = (string)value;
string newString = str.TrimEnd();//Newly added compared with the old version
if (newString == "income")
return new BitmapImage(new Uri("pack://application:,,,/images/add.png"));
if (newString == "Expenses")
{
//return new BitmapImage(new Uri(#"pack://application:,,,/HouseWivesSavior;component/images/add.png"));
return new BitmapImage(new Uri("pack://application:,,,/images/edit.png"));
}
return null;
}
From referring the above that you can see that I added this code: "string newString = str.TrimEnd();"
Is because I don't want extra white space at the end of the string. As during insert into the database that my code is look like this:
if (IncomeButton.IsChecked == true) {
CategoryType = IncomeButton.Content.ToString();
}else{
CategoryType = ExpensesButton.Content.ToString();
}
During runtime, I found out that why the value look strange in the format of "Expenses " instead of "Expenses"... Therefore I tried with trim of the end part see how & Bingo. I got it working like a charm.
I refered this video to out that how to trace the value: http://www.youtube.com/watch?v=evO3_xutDYI
Thank you all guys for answering my question & sorry for wasting your time & effort to solve my question :) Good luck to all of you & have a nice day.

WPF Binding from strings to Canvas objects in a ResourceDictionary using Converter

I have a ResourceDictionary made up of icons/Canvas objects drawn with Paths. My ViewModel includes a string property (IconName) that contains a string matching one of the entries in the ResourceDictionary. I developed a MultiBinding (IMultiValueConverter) that takes the string, and a FrameworkElement and does a resource lookup, returning the resource matching the name. Before getting to this point, I stubbed my View explicitly with the following:
<Rectangle Width="10" Height="10" Margin="0,0,10,0">
<Rectangle.Fill>
<VisualBrush Stretch="Fill" Visual="{StaticResource defalt_icon}" />
</Rectangle.Fill>
</Rectangle>
This renders correctly. However, when I switch out to the following, nothing is rendered in the Rectangle.
<Rectangle Width="10" Height="10" Margin="0,0,10,0">
<Rectangle.Fill>
<VisualBrush Stretch="Fill">
<VisualBrush.Visual>
<MultiBinding Converter="{StaticResource IconNameConverter}">
<MultiBinding.Bindings>
<Binding RelativeSource="{RelativeSource AncestorType=FrameworkElement}"/>
<Binding Path="IconName"/>
</MultiBinding.Bindings>
</MultiBinding>
</VisualBrush.Visual>
</VisualBrush>
</Rectangle.Fill>
</Rectangle>
My converter (show below) is being called, and does find the Canvas object and returns it (viewing the object in the debugger I can see that Canvas has a Path child that has the right Data member filled in).
public class IconNameConverter : IMultiValueConverter
{
public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
FrameworkElement targetElement = values[0] as FrameworkElement;
string iconName = values[1] as string;
if (iconName == null)
return null;
FrameworkElement newIcon = (FrameworkElement)targetElement.TryFindResource(iconName);
if (newIcon == null)
newIcon = (FrameworkElement)targetElement.TryFindResource("appbar_page_question");
return newIcon;
}
public object[] ConvertBack(object value, Type[] targetTypes, object parameter, System.Globalization.CultureInfo culture)
{
throw new NotImplementedException();
}
}
Any ideas why the canvas isn't showing up?

Converter not found? XamlParseException: Cannot find a Resource with the Name/Key StringTruncator

I've included the StringTruncator converter in my App.Resources
xmlns:app="clr-namespace:Tabbed_Browser">
<!--Application Resources-->
<Application.Resources>
<ResourceDictionary>
<app:StringTruncator x:Key="StringTruncator" />
<app:StringTruncatorFav x:Key="StringTruncatorFav" />
<app:AppInfo x:Key="AppInfo" />
<app:BooleanToVisibilityConverter x:Key="BooleanToVisibilityConverter" /
</ResourceDictionary>
</Application.Resources>
Then in the UserControl XML I refer to it via this code
<Grid x:Name="LayoutRoot" Background="{StaticResource PhoneChromeBrush}">
<TextBlock TextWrapping="NoWrap" x:Name="txtPageTitle"
Text="{Binding BrowserViewModel.PageTitle, Converter={StaticResource StringTruncator}}"
FontSize="{StaticResource PhoneFontSizeSmall}"
VerticalAlignment="Top"/>
The StringTruncator is a simple converter that append ... if the string exceed certain length.
namespace Tabbed_Browser
{
public class StringTruncator : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if (value == null)
return "";
string str = value.ToString();
int maxChars = 44;
return str.Length <= maxChars ? str : str.Substring(0, maxChars) + "...";
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
}
But then I run the project I get the following. Removing the StringTruncator converter in the code eliminate the error but I need to use the converter. What am I missing?
{System.Windows.Markup.XamlParseException:
Cannot find a Resource with the Name/Key StringTruncator [Line: 15 Position: 22]
at System.Windows.Application.LoadComponent(Object component, Uri resourceLocator)
at Tabbed_Browser.User_Controls.UCAddressBar.InitializeComponent()
at Tabbed_Browser.User_Controls.UCAddressBar..ctor()}

You should use DynamicResource instead, this way it will be applied at runtime. Or you can add resources to the Usercontrol.Resources itself. Or you can do like that also, but you must add namespace to UserControl also:
Text="{Binding BrowserViewModel.PageTitle, Converter={app:StringTruncator}}"