IValueConverter.Convert Method
[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]
Modifies the source data before passing it to the target for display in the UI.
Assembly: System.Windows (in System.Windows.dll)
'Declaration Function Convert ( _ value As Object, _ targetType As Type, _ parameter As Object, _ culture As CultureInfo _ ) As Object
Parameters
- value
- Type: System.Object
The source data being passed to the target.
- targetType
- Type: System.Type
The Type of data expected by the target dependency property.
- parameter
- Type: System.Object
An optional parameter to be used in the converter logic.
- culture
- Type: System.Globalization.CultureInfo
The culture of the conversion.
The culture is determined in the following order:
The converter looks for the ConverterCulture property on the Binding object.
If the ConverterCulture value is Nothing, the value of the Language property is used.
If the Convert method throws an exception, the binding engine ignores it and lets the exception bubble through.
If UnsetValue is returned, the target property is set to its default value.
The following example shows how to implement the Convert method using the parameter and culture parameters.
Imports System.Collections.ObjectModel Imports System.Windows.Data Partial Public Class Page Inherits PhoneApplicationPage Public MyMusic As New ObservableCollection(Of Recording)() Public Sub New() InitializeComponent() ' Add items to the collection. MyMusic.Add(New Recording("Sheryl Crow", "Detours", New DateTime(2008, 2, 5))) MyMusic.Add(New Recording("Brandi Carlisle", "The Story", New DateTime(2007, 4, 3))) MyMusic.Add(New Recording("Patty Griffin", "Children Running Through", New DateTime(2007, 2, 6))) ' Set the data context for the combo box. MusicCombo.DataContext = MyMusic End Sub End Class ' Simple business object. Public Class Recording Public Sub New() End Sub Public Sub New(ByVal artistName As String, ByVal cdName As String, _ ByVal release As DateTime) Artist = artistName Name = cdName ReleaseDate = release End Sub Private artistValue As String Private nameValue As String Private releaseDateValue As DateTime Public Property Artist() As String Get Return artistValue End Get Set(ByVal value As String) artistValue = value End Set End Property Public Property Name() As String Get Return nameValue End Get Set(ByVal value As String) nameValue = value End Set End Property Public Property ReleaseDate() As DateTime Get Return releaseDateValue End Get Set(ByVal value As DateTime) releaseDateValue = value End Set End Property End Class Public Class DateFormatter Implements IValueConverter ' This converts the DateTime object to the string to display. Public Function Convert(ByVal value As Object, ByVal targetType As Type, _ ByVal parameter As Object, ByVal culture As System.Globalization.CultureInfo) As Object _ Implements IValueConverter.Convert ' Retrieve the format string and use it to format the value. Dim formatString As String = TryCast(parameter, String) If Not String.IsNullOrEmpty(formatString) Then Return String.Format(culture, formatString, value) End If ' If the format string is null or empty, simply call ToString() ' on the value. Return value.ToString() End Function ' No need to implement converting back on a one-way binding. Public Function ConvertBack(ByVal value As Object, ByVal targetType As Type, _ ByVal parameter As Object, _ ByVal culture As System.Globalization.CultureInfo) As Object _ Implements IValueConverter.ConvertBack Throw New NotImplementedException() End Function End Class