3/9/2023 0 Comments Wpf colorconverter![]() So the first requirement is to map the current project into an XML namespace, making it possible to create a direct link between the two. And that DataTemplate is in Application.xaml.Īs things stand, the XAML markup is unable to access the code above directly. If you are wondering why the markup is in Application.xaml and not the Window that contains the ListView, the reason is that we need to set the conversion on the DataTemplate that formats the Quantity column. This is handled in the markup in the Application.xaml file. The second test in the Convert method checks the value of the current field and if it finds the value to be less than 200, Returns a Red Brush, otherwise it Returns a MediumBlue Brush.Ĭlearly, what is needed next is some mechanism that is watching for those returned values and making use of the particular brush that is returned. This isn't mandatory but is often worth including. ' Not used, so throw exception if this method is called.Īs you can see from the comments, I have chosen to test that a Brush object is passed in to the method. Public Function ConvertBack( ByVal value As Object, ByVal targetType As Type, _Īs Object Implements IValueConverter.ConvertBack Return ( If(Result < 200, Brushes.Red, Brushes.MediumBlue)) ' If less than 200 in stock, display in Red, otherwise useĭim Result As Integer = Integer.Parse(value.ToString()) ' Only allow conversion if the correct TargetType is passed in. Public Function Convert( ByVal value As Object, ByVal targetType As Type, _īyVal parameter As Object, ByVal culture As ) _Īs Object Implements IValueConverter.Convert First a couple of DataTemplates - one for the column header and for the cell: This will give an easy introduction to the steps involved.īefore getting round to the ValueConverter I need to add a new column to the ListView, the column that will display the quantities held in stock. Let's start with something simple, a ValueConverter that analyzes the quantity held in stock and if that value is less than a particular threshold, the figure is displayed in red in the ListView. This automatically intercepts the data as it is being fed in from the DataContext, analyzes the value and makes any appropriate settings or changes to the display of this piece of data. The way to achieve this kind of fine tuning is to use a ValueConverter. For instance, changing the color of the text if the value is negative. These will be displayed in a new column of the ListView.Īlthough the DataTemplates created earlier can alter the core properties of all the values in the column - Foreground, Bold font, etc,- they don't offer any mechanism for analyzing these values and changing the look of the display of an individual value based on some criteria. In the first example I will use integer values that represent the quantity of stock remaining of the various drink products. ![]() primitive types such as integer, double, boolean, etc. This data will often be in a raw state, e.g. By definition, this means that the data from the fields of the data source are passed untested from the source to the display. ValueConverters are particularly useful in situations where you are using data binding to directly populate elements in the UI. In this blog I want to demonstrate a simple example of the creation and use of a ValueConverter in WPF. There's a GradientBrush, a couple of Styles, then the DataTemplates, which are really only slightly tweaked versions of two simple templates.Īt this stage the ListView looks like this: If the Resources looks like a lot of markup, it breaks down into much less if you analyze it. All the Resources - GradientBrush, Styles, DataTemplates for ColumnHeaders and Cells - are in the Application.xaml file.
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