I have this listBox that gets populated, each item can be either male or female depending on the 'SEX' property that is binded to the listBox. (Could be either 'M' for male and 'F' for female)...
For each item i would like to display either a male or female symbol based on the list items SEX property.
for instance if "{Binding SEX}" equals 'M':
<Image Source="../Images/male48.png" Visibility="Visible" />
and if "{Binding SEX}" equals 'F':
<Image Source="../Images/female48.png" Visibility="Visible" />
How exactly would I go about getting this to work?
A common approach to this problem is to create a value converter, this converts the value returned by a binding into some other value that relates to the property of a UI control.
You can create a converter that takes the sex and maps it to an image source:
public class SexToSourceConverter : IValueConverter
{
public object Convert(object value, string typeName, object parameter, string language)
{
string url = ((string)value == "M") ? "../Images/male48.png" : "../Images/female48.png";
return new BitmapImage(new Uri(url , UriKind.Relative));
}
public object ConvertBack(object value, string typeName, object parameter, string language)
{
throw new NotImplementedException();
}
}
Using it in your XAML as follows:
<Image Source="{Binding Path=Sex, Converter={StaticResource SexToSourceConverter }" />
If someone is interested in how this could work, I've made a solution based on ColinE's answer. First, you've to create a new class which contain the conditions you'll like to add to the XAML code:
public class MyNiceConverterName : IValueConverter {
public object Convert(object value, Type targetType, object parameter, CultureInfo culture) {
// Your conditions here!
return value_you_want_to_return; // E.g., a string, an integer and so on
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) {
throw new NotImplementedException(); // Leave this like here, don't worry
}
}
Call the class whatever you want (right now it's called MyNiceConverterName) and implement the Convert() method with the conditions you'd like to add to the XAML file. Remember to cast the object value to the type you're using (e.g., (int)value if it's an integer).
This is almost done! But not yet, first declare the converter in your XAML as a resource. You can paste this code below the namespaces declaration:
<Control.Resources>
<converter:MyNiceConverterName xmlns:converter="clr-namespace:My_Namespace" x:Key="MyNiceConverterName" />
</Control.Resources>
You've to declare the namespace where you defined the class (i.e., remove My_Namespace with yours') and also rename MyNiceConverterName to your class name. The key will be the name defined to reference the converter within the XAML document, here I've used the same class name but you can freely change it.
Finally, it's time to use the converter. Put this and you're done:
{Binding variable_with_value, Converter={StaticResource MyNiceConverterName}}
Remember to change variable_with_value with the one you'd like to use within your binding.
I hope it helps!
Either use a binding converter or use two triggers.
For Siverlight this is the correct IValueConverter link, I am not sure if triggers are supported.
Related
Hi I've been looking at ways to dynamically change an image Uri in xaml and in my research came across the following answer, which has certainly given me hope that what I really want to do might just be possible. In the original question the questioner wanted to swap the image itself, in my case I want to swap the directory where the image is located.
So when one looks at the answer that #Clemens provided one ends up with an images source being bound to a dependency property that is dynamically set when the form loads.
What I'd like to know is whether it would be feasible to set the location part of the uri dynamically (as per the logic that #Clemens is advocating and then simply append the Image name in the actual binding statement so that it might look something like this:
<Image Source="{Binding ImageUri & myImage.png}"/>
Essentially I have a number of buttons to which I would like to assign a default image og a size to be determined by the end user. To that end the Images would be stored in different folders in the application (in fact its a custom control) and then the relevant path bit of the URI would be set as per the suggestion in the referenced answer and I'd just append the Image name (which would be the same for the button irrespective of the size) and it would then have the correct image to display.
MainWindow.xaml.cs :
namespace MainWindowNamespace
{
public sealed class ImageConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
try
{
string fullPath = Path.GetFullPath((string)value);
return new BitmapImage(new Uri(fullPath));
}
catch { return null; }
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{ throw new NotImplementedException(); }
}
}
MainWindow.xaml :
<Window
xmlns:imgConvert="clr-namespace:MainWindowNamespace">
<Window.Resources>
<imgConvert:ImageConverter x:Key="ImageConverter" />
</Window.Resources>
<Image ImageSource="{Binding ImagePath, Converter={StaticResource ImageConverter}}" />
</Window>
I was wondering if it is possible to hide a control on a view if the property to which the control is bound does not exist in the view model. For example, if I have the following:
<CheckBox Content="Quote"
IsChecked="{Binding Path=IsQuoted}" />
Can I detect in XAML that the IsQuoted property does not exist on the view model, and simply hide the control in that instance.
I am essentially creating a wizard dialog that moves through a collection of view models, displaying the associated view for each one. For some of the view models in the collection, the "IsQuoted" property will be present, and for some not.
I would like to have a check box outside of these views that displays when the current view model has the property, and hides when the view model does not. All of the view models are derived from a common base class, but I would rather not clutter the base by adding a "ShowQuoted" property, etc.
Thoughts? And, thanks in advance...
Handle the case where it the value is present by using a converter which always returns Visibility.Visible. Handle the case where the value isn't present by specifying a fallback value. When the property isn't present the binding fails and receives the fallback value.
<Page.DataContext>
<Samples:OptionalPropertyViewModel/>
</Page.DataContext>
<Grid>
<Grid.Resources>
<Samples:AlwaysVisibleConverter x:Key="AlwaysVisibleConverter" />
</Grid.Resources>
<CheckBox
Content="Is quoted"
IsChecked="{Binding IsQuoted}"
Visibility="{Binding IsQuoted,
Converter={StaticResource AlwaysVisibleConverter},
FallbackValue=Collapsed}"
/>
</Grid>
public class OptionalPropertyViewModel
{
public bool IsQuoted { get; set; }
}
public class AlwaysVisibleConverter : IValueConverter
{
#region Implementation of IValueConverter
public object Convert(object value,
Type targetType, object parameter, CultureInfo culture)
{
return Visibility.Visible;
}
public object ConvertBack(object value, Type targetType,
object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
#endregion
}
I have binding to Image.Source and TextBlocks. Also I have own convertor classes.
<conv:StatusConvertor x:Key="statusConvertor"></conv:StatusConvertor>
<conv:ImageConvertor x:Key="imageConvertor"></conv:ImageConvertor>
For example:
<Image Source="{Binding Value.profilePhoto, Converter={StaticResource imageConvertor}}" Margin="4,4,4,2"/>
<TextBlock Name="tbStatus" Text="{Binding Value.status,Converter={StaticResource statusConvertor}}" Grid.Column="0" Grid.Row="2" Margin="2,2,2,2" FontSize="11" FontWeight="Normal"></TextBlock>
I want set condition for imageConvertor, for example:
IF tbStatus.Text=="0"
THEN use imageConvertor on Image.Source
It’s possible this write in XAML, maybe in convertor class?
Instead of making your ImageConverter an IvalueConverter, make it an IMultiValueConverter:
<Image Margin="4,4,4,2">
<Image.Source>
<MultiBinding Converter="{StaticResource imageConvertor}">
<Binding Path="Value.profilePhoto" />
<Binding Path="Value.status" />
</MultiBinding>
</Image.Source>
</Image>
A IMultiValueConverter is the same as an IValueConverter, except that it passes an array of objects instead of a single object value.
public object Convert(object[] values,
Type targetType, object parameter, CultureInfo culture)
{
// Use your converter code from before, but add a check for the Status value
// as well
string path = values[0].ToString();
int status = Int32.Parse(values[1].ToString();
if (status == 0)
return newImageSource;
return DependencyProperty.UnsetValue;
}
Here is is tough for me to guess on the design of your current converter, but this gives you a rough idea on what to do. I am implying from your question that if the status is not 0, you don't want your converter to return anything - hence the DependencyProperty.UnsetValue.
I don't think it's possible to do this in XAML.
I'm pretty sure it's impossible to do (as is) in the converter because you don't have access to the sender (here a TextBlock) within.
EDIT : you can do it with a multivalue converter, because you need OneWay Binding. Multivalue converters are difficult to set up with a TwoWay binding (when you need the ConvertBack method).
What I would do would be to declare two Images (one with for each value of your TextBlock : 0 and else) and bind the visibility to the textblock Text value (or directly to Value.status).
This doesn't specifically answer the question, but I managed to solve my problem using this question as a guide, so I thought it might help future searchers. It could probably also be extended further to solve the original question with a little more work.
I was trying to find a way of evaluating an IF-conditional expression within XAML and wanted to combine the power of a Binding expression and a MarkupExtension. Using the idea of a converter, I managed to create a ConditionalMarkupConverter. This has two properties to specify the values to be returned when a binding expression evaluates to true or false, and since it's a converter, it can be easily added to a binding expression.
Converter
public sealed class ConditionalMarkupConverter : MarkupExtension, IValueConverter
{
public object TrueValue { get; set; }
public object FalseValue { get; set; }
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if (value is bool && (bool)value)
{
// The given value has evaluated to true, so return the true value
return TrueValue;
}
// If we get here, the given value does not evaluate to true, so default to the false value
return FalseValue;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotSupportedException();
}
}
public override object ProvideValue(IServiceProvider serviceProvider)
{
return this;
}
XAML
<TextBlock Text="{Binding IsActive, Converter={converters:ConditionalMarkupConverter TrueValue=Active, FalseValue=Inactive}}" />
In this example, the TextBlock binds to a boolean property called IsActive and the converter then returns the string "Active" when IsActive is true, or "Inactive" when IsActive is false.
I have a data source ('SampleAppearanceDefinitions'), which holds a single collection ('Definitions'). Each item in the collection has several properties, including Color, which is what I'm interested in here.
I want, in XAML, to display the Color of a particular item in the collection as text. I can do this just fine using this code below...
Text="{Binding Source={StaticResource SampleAppearanceDefinitions}, Path=Definitions[0].Color}"
The only problem is, this requires me to hard-code the index of the item in the Definitions collection (I've used 0 in the example above). What I want to do in fact is to get that value from a property in my current DataContext ('AppearanceID'). One might imagine the correct code to look like this....
Text="{Binding Source={StaticResource SampleAppearanceDefinitions}, Path=Definitions[{Binding AppearanceID}].Color}"
...but of course, this is wrong.
Can anyone tell me what the correct way to do this is? Is it possible in XAML only? It feels like it ought to be, but I can't work out or find how to do it.
Any help would be greatly appreciated!
Thanks!
AT
MultiBinding is your friend here:
Assuming you have a TextBlock:
<TextBlock>
<TextBlock.Text>
<MultiBinding Converter="{StaticResource AppearanceIDConverter}">
<Binding Source="{StaticResource SampleAppearanceDefinitions}" />
<Binding Path="AppearanceID" />
</MultiBinding>
</TextBlock.Text>
</TextBlock>
And define a MultiValueConverter to return what you wish to see:
public class AppearanceIDConverter : IMultiValueConverter
{
#region IMultiValueConverter Members
public object Convert(object[] values, System.Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
List<item> items = (List<item>)values[0]; //Assuming its items in a List
int id = (int)values[1]; //Assuming AppearanceID is an integer
return items.First(i => i.ID == id).Color; //Select your item based on the appearanceID.. I used LINQ, but a foreach will work just fine as well
}
public object[] ConvertBack(object value, System.Type[] targetTypes, object parameter, System.Globalization.CultureInfo culture)
{
throw new System.NotImplementedException();
}
#endregion
}
Of course, you will need to set the converter as a resource in your Resource dictionary, like you did SampleAppearanceDefinitions. You can also ditch the multibinding and use a regular binding to AppearanceID with a IValueConverter, if you can get to the SampleAppearanceDefinitions collection through code ;).
Hope this helps
Even if it could be possible you'd better not do that this way, but instead use a dedicated property in your view model or in the code behind of your view if it has only a pure graphical meaning.
This property, say "CurrentAppearance", would expose a Color property you could bind from your Xaml :
Text="{Binding CurrentAppearance.Color}"
which is more understandable.
As a general advice : avoid to spoil your Xaml with plumbing code : Xaml should be as readable as possible,
particularly if you work with a team of designers that have no coding skills and do not want to be concerned with the way you are managing the data.
Moreover, if later you decide to change the way data are managed you would not have to change your Xaml.
MultiBinding might actually work if your list is on a viewmodel instead of a staticresource. I was suprised myself to see that the object passed on to the view is actually a pointer to the object on the model, so changing the object in the view (eg. typing in new test in the textbox) directly affects the model object.
This worked for me. The ConvertBack method is never useed.
public class PropertyIdToPropertyConverter : IMultiValueConverter
{
public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
{
if (values.Length == 2)
{
var properties = values[0] as ObservableCollection<PropertyModel>;
if (properties != null)
{
var id = (int)values[1];
return properties.Where(model => model.Id == id).FirstOrDefault();
}
}
return null;
}
public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
I have a grid with 2 columns, a listbox in column 0 and a number of other controls in the a secondary grid in the main grids column 1.
I want this controls only to be enabled (or perhaps visible) if an items is selected in the listbox through binding. I tried on a combo box:
IsEnabled="{Binding myList.SelectedIndex}"
But that does not seem to work.
Am I missing something? Should something like this work?
thanks
You'll need a ValueConverter for this. This article describes it in detail, but the summary is you need a public class that implements IValueConverter. In the Convert() method, you could do something like this:
if(!(value is int)) return false;
if(value == -1) return false;
return true;
Now, in your XAML, you need to do:
<Window.Resources>
<local:YourValueConverter x:Key="MyValueConverter">
</Window.Resources>
And finally, modify your binding to:
IsEnabled="{Binding myList.SelectedIndex, Converter={StaticResource MyValueConverter}"
Are you sure you didn't mean
IsEnabled="{Binding ElementName=myList, Path=SelectedIndex, Converter={StaticResource MyValueConverter}"
though? You can't implicitly put the element's name in the path (unless the Window itself is the DataContext, I guess). It might also be easier to bind to SelectedItem and check for not null, but that's really just preference.
Oh, and if you're not familiar with alternate xmlns declarations, up at the top of your Window, add
xmlns:local=
and VS will prompt you for the various possibilities. You need to find the one that matches the namespace you put the valueconverter you made in.
Copy-paste solution:
Add this class to your code:
public class HasSelectedItemConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
return value is int && ((int) value != -1);
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
Add converter as StaticResource to App.xml in <Application.Resources> section:
<local:HasSelectedItemConverter x:Key="HasSelectedItemConverter" />
And now you can use it in your XAML:
<Button IsEnabled="{Binding ElementName=listView1, Path=SelectedIndex,
Converter={StaticResource HasSelectedItemConverter}"/>
Hmm, perhaps it works with a BindingConverter, which converts explicitly all indexes > 0 to true.