Common Converters in WPF/Silverlight
using System; using System.ComponentModel; using System.Globalization; using System.Windows.Data; namespace WPFComponents { [ValueConversion(typeof(string), typeof(int))] public class StringToIntegerConverter : IValueConverter { public object Convert(object value, Type targetType, object parameter, CultureInfo culture) { return System.Convert.ToInt32(value); } public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) { return System.Convert.ToString(value); } } }
using System; using System.ComponentModel; using System.Globalization; using System.Windows.Data; namespace WPFComponents { [ValueConversion(typeof(string), typeof(string))] public class StringToLowerCaseConverter : IValueConverter { public object Convert(object value, Type targetType, object parameter, CultureInfo culture) { return System.Convert.ToString(value).ToLower(); } public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) { return System.Convert.ToString(value); } } }
using System; using System.ComponentModel; using System.Globalization; using System.Windows.Data; using System.Xml; namespace WPFComponents { [ValueConversion(typeof(XmlElement), typeof(decimal))] public class XmlElementToDecimalConverter : IValueConverter { public object Convert(object value, Type targetType, object parameter, CultureInfo culture) { return System.Convert.ToDecimal(((XmlElement)value).InnerText); } public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) { return System.Convert.ToString(value); } } }
using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Globalization; using System.ComponentModel; using System.Windows.Data; using System.Windows; using System.Windows.Controls; namespace WPFComponents { [ValueConversion(typeof(ListBoxItem), typeof(Thickness))] public class IndexToMarginConverter : IValueConverter { public object Convert(object value, Type targetType, object parameter, CultureInfo culture) { Thickness ret; int itemIndex; ListBoxItem lstItem; ListBox lstBox; lstItem = (value as ListBoxItem); lstBox = (ListBox)ItemsControl.ItemsControlFromItemContainer(lstItem); itemIndex = lstBox.ItemContainerGenerator.IndexFromContainer(lstItem); if ((itemIndex % 2) != 0) ret = new Thickness(5, 0, 30, 30); else ret = new Thickness(30, 25, 0, 0); return ret; } public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) { throw new NotImplementedException(); } } }
using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Globalization; using System.ComponentModel; using System.Windows.Data; using System.Windows; using System.Windows.Controls; namespace WPFComponents { [ValueConversion(typeof(ListBoxItem), typeof(decimal))] public class IndexToAngleConverter : IValueConverter { public const int ANGLE = 15; public object Convert(object value, Type targetType, object parameter, CultureInfo culture) { double ret; int itemIndex; ListBoxItem lstItem; ListBox lstBox; // The 'value' parameter is the ListBoxItem lstItem = (value as ListBoxItem); // Get a reference to the list box so we can get the index of which item is being drawn lstBox = (ListBox)ItemsControl.ItemsControlFromItemContainer(lstItem); // Get the index of the item being drawn itemIndex = lstBox.ItemContainerGenerator.IndexFromContainer(lstItem); if ((itemIndex % 2) != 0) ret = ANGLE; else ret = -(ANGLE); return ret; } public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) { throw new NotImplementedException(); } } }
using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Windows.Data; namespace Halliburton.Castor.Views.Converter { class DateToDayStringConverter : IValueConverter { public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) { DateTime? date = (DateTime?)value; return date.HasValue ? date.Value.Day.ToString() : "1"; } public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) { throw new NotImplementedException(); } } }
using System; using System.Collections.Generic; using System.Globalization; using System.Linq; using System.Text; using System.Windows.Data; namespace Halliburton.Castor.Views.Converter { class EnumMatchToBooleanConverter : IValueConverter { public object Convert(object value, Type targetType, object parameter, CultureInfo culture) { if (value == null || parameter == null) return false; string checkValue = value.ToString(); string targetValue = parameter.ToString(); return checkValue.Equals(targetValue, StringComparison.InvariantCultureIgnoreCase); } public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) { if (value == null || parameter == null) return null; bool useValue = (bool)value; string targetValue = parameter.ToString(); if (useValue) return Enum.Parse(targetType, targetValue); return null; } } }
public class InverseBooleanConverter<bool> : ValueConverter { protected override bool Convert(bool value, Type targetType, object parameter, CultureInfo culture) { return !value; } protected override bool ConvertBack(bool value, Type targetType, object parameter, CultureInfo culture) { return !value; } }
public class BoolToVisibilityConverter<bool,Visibility> : ValueConverter { protected override Visibility Convert(bool value, Type targetType, object parameter, CultureInfo culture) { return value ? Visibility.Visible : Visibility.Collapsed; } protected override bool ConvertBack(Visibility value, Type targetType, object parameter, CultureInfo culture) { return value == Visibility.Visible; } }
Byte Array to Image Converter
ByteToImageConverter will convert byte array of image to a BitmapImage which can be used in Source property of an image. This can be used when we have an image saved in binary form in database and we want to bind that and show in image control. We can show a default image if byte array is null by uncommenting the code in “else” part of BitmapToImageConverter class.
public class ByteToImageConverter : IValueConverter { public BitmapImage ConvertByteArrayToBitMapImage(byte[] imageByteArray) { BitmapImage img = new BitmapImage(); using (MemoryStream memStream = new MemoryStream(imageByteArray)) { img.SetSource(memStream); } return img; } public object Convert(object value, Type targetType, object parameter, CultureInfo culture) { BitmapImage img = new BitmapImage(); if (value != null) { img = this.ConvertByteArrayToBitMapImage(value as byte[]); } else { //img = new BitmapImage(new Uri("/AssemblyName;component/Images/defaultImage.jpg", UriKind.Relative)); img = null; } return img; } public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) { return null; } }
<Image Margin="3" Source="{Binding Path=ByteArray, Converter={StaticResource byteToImageConverter}}"/>
Null or Empty Visibility Converter
NullEmptyVisibilityConverter can be used if we don’t want to show the control if value in binding is null. In above class, we are setting Visibility property as Collapsed if value is null or if string type value is null or empty.
public class NullEmptyVisibilityConverter : IValueConverter { public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) { if (value == null) { return Visibility.Collapsed; } else if (value.GetType() == typeof(string) && string.IsNullOrWhiteSpace(value.ToString()) == true) { return Visibility.Collapsed; } else { return Visibility.Visible; } } public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) { throw new Exception("Not implemented"); } }
<TextBlock Margin="3" Text="{Binding Path=Data, Converter={StaticResource nullVisibilityConverter}}"/>
Negative Converter
Sometime we want to display reverse result of the binded value. For example, we want to disable the control if value is true. Now the disable control we have to set IsEnabled = false and we have value of true to disable. So in this case we can use above NegativeConverter.
In above example code, we are unchecking the chkSecond checkbox if chkFirst checkbox is checked and vice versa. So for this we are setting staticResource of NegativeConverter in binding converter property
Public Class NegativeConverter Implements IValueConverter Public Function Convert(value As Object, targetType As Type, parameter As Object, culture As System.Globalization.CultureInfo) As Object Implements IValueConverter.Convert If value.[GetType]() Is GetType(Boolean) Then Dim result As Boolean = CBool(value) Return Not result Else Return value End If End Function Public Function ConvertBack(value As Object, targetType As Type, parameter As Object, culture As System.Globalization.CultureInfo) As Object Implements IValueConverter.ConvertBack Throw New Exception("Not implemented") End Function End Class
<StackPanel Orientation="Vertical"> <CheckBox HorizontalAlignment="Left" Margin="3" Width="100" Height="25" Name="chkFirst"/> <CheckBox Name="chkSecond" HorizontalAlignment="Left" Margin="3" Height="25" IsChecked="{Binding Path=IsChecked, ElementName=chkFirst, Converter={StaticResource negativeConverter}}"/> </StackPanel>
Multiplication Converter
In the above code in txtSecond
textbox we are binding it’s width property to txtFirst textbox width property. So we have set ElementName as
txtFirst and Path as
ActualWidth. And we want to have txtSecond width double of txtFirst. So we would be setting staticresource of MultiplyConverter in converter property and “2.0” as ConverterParameter property.
Now in MultiplyConverter class we would have ActualWidth of txtFirst in value parameter and “2.0” in “parameter” parameter. So we will multiply the two value and return the result.
Public Class MultiplyConverter Implements IValueConverter Public Function Convert(value As Object, targetType As Type, parameter As Object, culture As System.Globalization.CultureInfo) As Object Implements IValueConverter.Convert If parameter IsNot Nothing Then Dim result As Double = Double.Parse(parameter.ToString()) Return CDbl(value) * result Else Return CDbl(value) End If End Function Public Function ConvertBack(value As Object, targetType As Type, parameter As Object, culture As System.Globalization.CultureInfo) As Object Implements IValueConverter.ConvertBack Throw New Exception("Not implemented") End Function
<StackPanel Orientation="Vertical"> <TextBox HorizontalAlignment="Left" Margin="3" Width="100" Height="25" Name="txtFirst"/> <TextBox Name="txtSecond" HorizontalAlignment="Left" Margin="3" Height="25" Width="{Binding Path=ActualWidth, ElementName=txtFirst, Converter={StaticResource multiplyConverter}, ConverterParameter=2.0}"/> </StackPanel>
Divide Converter
Similar to Multiplication Converter, in the above code in txtSecond textbox we are binding it’s width property to txtFirst textbox width property. So we have set ElementName as
txtFirst and Path as
ActualWidth. And we want to have txtSecond width half of txtFirst. So we would be setting staticresource of DivideConverter in converter property and “2.0” as ConverterParameter property.
Now in DivideConverter class we would have ActualWidth of txtFirst in value parameter and “2.0” in “parameter” parameter. So we will divide the ActualWidth by “2.0” and return the result.
Public Class DivideConverter Implements IValueConverter Public Function Convert(value As Object, targetType As Type, parameter As Object, culture As System.Globalization.CultureInfo) As Object Implements IValueConverter.Convert If parameter IsNot Nothing Then Dim result As Double = Double.Parse(parameter.ToString()) If result > 0 Then Return CDbl(value) / result Else Return CDbl(value) End If Else Return CDbl(value) End If End Function Public Function ConvertBack(value As Object, targetType As Type, parameter As Object, culture As System.Globalization.CultureInfo) As Object Implements IValueConverter.ConvertBack Throw New Exception("Not implemented") End Function End Class
<StackPanel Orientation="Vertical"> <TextBox HorizontalAlignment="Left" Margin="3" Width="100" Height="25" Name="txtFirst"/> <TextBox Name="txtSecond" HorizontalAlignment="Left" Margin="3" Height="25" Width="{Binding Path=ActualWidth, ElementName=txtFirst, Converter={StaticResource divideConverter}, ConverterParameter=2.0}"/> </StackPanel>
Subtract Converter
Here we want txtSecond textbox, 15 pixels less than txtFirst. In above code in txtSecond textbox we are binding it’s width property to txtFirst textbox width property. So we have set ElementName as
txtFirst and Path as
ActualWidth. And as we want to have txtSecond 15 pixels less than txtFirst, we would be setting staticresource of SubtractConveter in converter property and “15.0” as ConverterParameter property.
Now in SubtractConverter class we would have ActualWidth of txtFirst in value parameter and “15.0” in “parameter” parameter. So we will subtract 15 from ActualWidth and return the result.
Public Class SubtractConverter Implements IValueConverter Public Function Convert(value As Object, targetType As Type, parameter As Object, culture As System.Globalization.CultureInfo) As Object Implements IValueConverter.Convert If parameter IsNot Nothing Then Dim result As Double = Double.Parse(parameter.ToString()) Return CDbl(value) - result Else Return CDbl(value) End If End Function Public Function ConvertBack(value As Object, targetType As Type, parameter As Object, culture As System.Globalization.CultureInfo) As Object Implements IValueConverter.ConvertBack Throw New Exception("Not implemented") End Function End Class
<StackPanel Orientation="Vertical"> <TextBox HorizontalAlignment="Left" Margin="3" Width="100" Height="25" Name="txtFirst"/> <TextBox Name="txtSecond" HorizontalAlignment="Left" Margin="3" Height="25" Width="{Binding Path=ActualWidth, ElementName=txtFirst, Converter={StaticResource subtractConverter}, ConverterParameter=15.0}"/> </StackPanel>