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 % ) != )
        ret = new Thickness(, , , );
      else
        ret = new Thickness(, , , );

      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 = ;

    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 % ) != )
        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() : "";
        }

        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 >  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>