Como: Converter Dados Acoplados
This example shows how to apply conversion to data that is used in bindings.
To convert data during binding, you must create a class that implements the IValueConverter interface, which includes the Convert and ConvertBack methods.
Exemplo
The following example shows the implementation of a date converter that converts the date value passed in so that it only shows the year, the month, and the day. When implementing the IValueConverter interface, it is a good practice to decorate the implementation with a ValueConversionAttribute attribute to indicate to development tools the data types involved in the conversion, as in the following example:
[ValueConversion(typeof(DateTime), typeof(String))]
public class DateConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
DateTime date = (DateTime)value;
return date.ToShortDateString();
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
string strValue = value as string;
DateTime resultDateTime;
if (DateTime.TryParse(strValue, out resultDateTime))
{
return resultDateTime;
}
return DependencyProperty.UnsetValue;
}
}
Once you have created a converter, you can add it as a resource in your Extensible Application Markup Language (XAML) file. In the following example, src maps to the namespace in which DateConverter is defined.
<src:DateConverter x:Key="dateConverter"/>
Finally, you can use the converter in your binding using the following syntax. In the following example, the text content of the TextBlock is bound to StartDate, which is a property of an external data source.
<TextBlock Grid.Row="2" Grid.Column="0" Margin="0,0,8,0"
Name="startDateTitle"
Style="{StaticResource smallTitleStyle}">Start Date:</TextBlock>
<TextBlock Name="StartDateDTKey" Grid.Row="2" Grid.Column="1"
Text="{Binding Path=StartDate, Converter={StaticResource dateConverter}}"
Style="{StaticResource textStyleTextBlock}"/>
Os recursos de estilo referenciados no exemplo acima são definidos em uma seção de recursos não mostrada neste tópico.
Consulte também
Tarefas
Como: Implement Binding Validation
Conceitos
Revisão de Associação de Dados