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How to Implement a DependencyPropertyWatcher

Dependency properties are widely used in WPF controls. However there is no buid-in way to listen to changes of such properties. The following class is a generic watcher for dependecy properties: public class DependencyPropertyWatcher<T> : DependencyObject, IDisposable { /// <summary> /// Value of Value Property /// </summary> public static readonly DependencyProperty ValueProperty = DependencyProperty.Register( „Value“, […]

Creating ComboBox with System Colors in XAML

This snippet shows how to display a list of system colors in XAML only. First we create ab object data source containing the list of colors: <ObjectDataProvider ObjectInstance=“{x:Type Colors}“ MethodName=“GetProperties“ x:Key=“ListOfColors“ /> This data source obtains the list of colors from the properties of the Colors type. In the next step we define a data […]

Data Binding to Visibility Property

The following describes how to used a converter to directly bind your ViewModel properties to the Visibility of controls in your view. First we define a converter that converts a boolean value into a Visibility enum value and back. [ValueConversion(typeof(bool), typeof(Visibility))] public class VisibilityConverter : IValueConverter { public object Convert(object value, Type targetType, object parameter, […]

ViewModel Validation in MVVM

In WPF IValidatableObject, IDataErrorInfo interface implementations can be used to validate user input against validation rules. This blow shows a different approach that defines a IValidatingViewModel as interface for ViewModels that should use a validation. This is a very simple approach without relying on some black box third party technology. Validation Interface This is the […]

Loading Files into a WPF FlowDocument

Das WPF FlowDocument ist eine einfache Möglichkeit, um Fließtext in WPF darzustellen. Hier zeige ich Methoden, um Textdateien in ein FlowDocument einzulesen. XAML: <FlowDocumentScrollViewer x:Name=“documentViewer“ /> Loading of a text file: string fileName = @“Lizenz.txt“; if (File.Exists(fileName)) { var run = new Run(File.ReadAllText(fileName)); var p = new Paragraph(run); var flowDocument = new FlowDocument(p); documentViewer.Document = […]

Using Data Annotations for Validation in WPF

The .NET Framework uses many different approaches for validation. The ASP.NET MVC for example uses Data Annotations to annotate the model classes with the definition of valid ranges, etc. In WPF on the other hand, validation rules are used to validate entries made by the user and display error messages. This post shows how to […]

WPF Fix: Style is Only Applied to First Element

There is a bug in WPF that leads to a very strange behavior: A style that is defined in the resources is not applied to the first element, but to all others. This only happens when MergedDictionaries are cascaded. The following code is a valid XAML definition, but will not work as expected: <Application.Resources> <ResourceDictionary> […]

Automatically grayed Image in WPF

The following class is a WPF image control which is directly derived from Image. Therefore it can be used out-of-the-box like the standard WPF Image control. The image will automatically change to a gray scale image when the IsEnabled property of the control is set to false. The AutoGrayableImage can be used in within any […]

Text Drop Shadow Effect in XAML

A DropShadowEffect can be used to make any WPF control cast a shadow. In order to use this on a text, we can simply assign the effect to the Effect property of the TextBlock. DropShadowEffect contains properties to set the shadow depth, the direction, color of the shadow, opacity and a blur radius. This gives […]