WPF conditional convertor - wpf

Question

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?

Answer 1

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.

Answer 2

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).

Answer 3

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.