ValueConversionAttribute Class
Represents an attribute that allows the author of a value converter to specify the data types involved in the implementation of the converter.
Assembly: PresentationFramework (in PresentationFramework.dll)
The ValueConversionAttribute type exposes the following members.
| Name | Description | |
|---|---|---|
 | ValueConversionAttribute | Initializes a new instance of the ValueConversionAttribute class with the specified source type and target type. |
| Name | Description | |
|---|---|---|
| ParameterType | Gets and sets the type of the optional value converter parameter object. |
| SourceType | Gets the type this converter converts. |
| TargetType | Gets the type this converter converts to. |
| TypeId | Gets the unique identifier of this ValueConversionAttribute instance. (Overrides Attribute.TypeId.) |
| Name | Description | |
|---|---|---|
| Equals | Infrastructure. Returns a value that indicates whether this instance is equal to a specified object. (Inherited from Attribute.) |
| Finalize | Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.) |
| GetHashCode | Returns the hash code for this instance of ValueConversionAttribute. (Overrides Attribute.GetHashCode.) |
| GetType | Gets the Type of the current instance. (Inherited from Object.) |
| IsDefaultAttribute | When overridden in a derived class, indicates whether the value of this instance is the default value for the derived class. (Inherited from Attribute.) |
| Match | When overridden in a derived class, returns a value that indicates whether this instance equals a specified object. (Inherited from Attribute.) |
| MemberwiseClone | Creates a shallow copy of the current Object. (Inherited from Object.) |
| ToString | Returns a string that represents the current object. (Inherited from Object.) |
| Name | Description | |
|---|---|---|
| _Attribute.GetIDsOfNames | Maps a set of names to a corresponding set of dispatch identifiers. (Inherited from Attribute.) |
| _Attribute.GetTypeInfo | Retrieves the type information for an object, which can be used to get the type information for an interface. (Inherited from Attribute.) |
| _Attribute.GetTypeInfoCount | Retrieves the number of type information interfaces that an object provides (either 0 or 1). (Inherited from Attribute.) |
| _Attribute.Invoke | Provides access to properties and methods exposed by an object. (Inherited from Attribute.) |
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.
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:
Public Class DateConverter Implements System.Windows.Data.IValueConverter Public Function Convert(ByVal value As Object, ByVal targetType As System.Type, ByVal parameter As Object, ByVal culture As System.Globalization.CultureInfo) _ As Object Implements System.Windows.Data.IValueConverter.Convert Dim DateValue As DateTime = CType(value, DateTime) Return DateValue.ToShortDateString End Function Public Function ConvertBack(ByVal value As Object, ByVal targetType As System.Type, ByVal parameter As Object, ByVal culture As System.Globalization.CultureInfo) _ As Object Implements System.Windows.Data.IValueConverter.ConvertBack Dim strValue As String = value Dim resultDateTime As DateTime If DateTime.TryParse(strValue, resultDateTime) Then Return resultDateTime End If Return DependencyProperty.UnsetValue End Function End Class
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}"/>
The style resources referenced in the above example are defined in a resource section not shown in this topic.
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.