ValueConverters
Introduction
If you want to databind two properties that have incompatible types, you need a piece of code in between, that converts the value from source to target type and back. This piece of code is called ValueConverter. A value converter is a class, that implements the simple interface IValueConverter with the two methods object Convert(object value) and object ConvertBack(object value) .
How to implement a ValueConverter
WPF already provides a few value converts, but you will soon need to implement your own converts. To do this, add a class to your project and call it [SourceType]To[TargetType]Converter . This is a common naming for value converters. Make it public and implement the IValueConverter interface. That's all you need to do.
How to use a ValueConverter in XAML
First thing you need to do is to map the namespace of your converter to a XAML namespace. Then you can create an instance of a value converter in the resources of the view and give it a name. Then you can reference it by using
Simplify the usage of ValueConvers
If you want to use a normal ValueConverter in XAML, you have to add an instance of it to the resources and reference it by using a key. This is cumbersome, because and the key is typically just the name of the converter.
A simple and cool trick is to derive value converters from MarkupExtension . This way you can create and use it in the binding like this: Text=> , and that is quite cool!
Wpf value converter color
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How do I convert a Color to a Brush in XAML?
I want to convert a System.Windows.Media.Color value to a System.Windows.Media.Brush. The color value is databound to a Rectangle object's Fill property. The Fill property takes a Brush object, so I need an IValueConverter object to perform the conversion.
Is there a built-in converter in WPF or do I need to create my own? How do I go about creating my own if it becomes necessary?
It seems that you have to create your own converter. Here a simple example to start:
To use it, declare it in the resource-section.
And the use it in the binding as a static resource:
I have not tested it. Make a comment if its not working.
I know I am really late to the party, but you don't need a converter for this.
I wanted to do this HCL's way rather than Jens' way because I have a lot of things bound to the Color , so there's less duplication and boiler-plate .Fill nodes.
However when trying to write it, ReSharper pointed me to the WPF Toolkit's implementation of the ColorToSolidColorBrushConverter. You need to include the following namespace declaration in the main Window/UserControl node:
Then a static resource in the Window/UserControl resources:
Then you can do it like HCL's answer:
With some more enhancment to HCL answer, I tested it - it works.
A Converter is not needed here. You can define a Brush in XAML and use it. It would be better to define the Brush as a Resource so it can be used other places required.
Wpf value converter color
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use of boolean to color converter in XAML
I am working on WPF application.I have bound my textblock to my button. I want to set foreground of my textblock to black color when its associated button's isEnabled is true. I want to do this using converter. But its not working. also not giving any error. I have declared following class in my "Models" folder.
Button's enable,isable property changes from viewmodel(e.g using RaiseCanExecuteChanged)())
textblock related things in XAML are:
use return new SolidColorBrush(Colors.Black);
The answer above shows you how to correctly you use a converter. However, do you really need to use a converter? This can be done in XAML only using Triggers :
In the example above, the first TextBlock binds to its parent's IsEnabled property using a DataTrigger , and sets the Foreground to some colour if it is true.
However, this is overkill - the IsEnabled property is propagated down to children automatically by WPF. That is, if you set IsEnabled to false on your Button , then your TextBlock will have its IsEnabled property updated to false automatically. This is demonstrated in the second TextBlock which uses a property Trigger to check its own IsEnabled property against the value of true (since its IsEnabled property will be the same as its parent's). This would be the preferred approach.
Hope this helps!
To make this converter general you may use a ConverterParameter for specifying the colors which is to be inserted when value is true or false. Also the opacity may be of interest. I here provide the Converter I taking the parameter [ColorNameIfTrue;ColorNameIfFalse;OpacityNumber].
Since the SolidColorBrush() method mentioned by @user1101511 is part of the System.Windows.Media library, it uses the Color type from that same library. This type does not have a Color.FromName() method, like the System.Drawing.Color class.
Therfore I made a helper method called ColorFromName(string name) . I specify "LimeGreen" as a fallback color if the interpertation of ConverterParameter fails. In my case I want the output to be "Transparent" when value is false.
From xaml the above converter may be used like this: