Binding converter as inner class?

Question

I have a UserControl that uses a binding converter. I\'ve made the converter an inner class of

public partial class MyPanel : UserControl
{
    public class          


        

Answer 1

It could be possible. A few months ago I wrote a markup extension to create the converter for you inline. It keeps a dictionary of weak references so that you don't create multiple instances of the same converter. Handles creating converters with different arguments too.

In XAML:

C#:

[MarkupExtensionReturnType(typeof(IValueConverter))]
public class InlineConverterExtension : MarkupExtension
{
  static Dictionary s_WeakReferenceLookup;

  Type m_ConverterType;
  object[] m_Arguments;

  static InlineConverterExtension()
  {
    s_WeakReferenceLookup = new Dictionary();
  }

  public InlineConverterExtension()
  {
  }

  public InlineConverterExtension(Type converterType)
  {
    m_ConverterType = converterType;
  }

  /// 

  /// The type of the converter to create
  /// 
  /// The type of the converter.
  public Type ConverterType
  {
    get { return m_ConverterType; }
    set { m_ConverterType = value; }
  }

  /// 

  /// The optional arguments for the converter's constructor.
  /// 
  /// The argumments.
  public object[] Arguments
  {
    get { return m_Arguments; }
    set { m_Arguments = value; }
  }

  public override object ProvideValue(IServiceProvider serviceProvider)
  {
    IProvideValueTarget target = (IProvideValueTarget)serviceProvider.GetService(typeof(IProvideValueTarget));

    PropertyInfo propertyInfo = target.TargetProperty as PropertyInfo;

    if (!propertyInfo.PropertyType.IsAssignableFrom(typeof(IValueConverter)))
      throw new NotSupportedException("Property '" + propertyInfo.Name + "' is not assignable from IValueConverter.");

    System.Diagnostics.Debug.Assert(m_ConverterType != null, "ConverterType is has not been set, ConverterType{x:Type converterType}");

    try
    {
      string key = m_ConverterType.ToString();

      if (m_Arguments != null)
      {
        List args = new List();
        foreach (object obj in m_Arguments)
          args.Add(obj.ToString());

        key = String.Concat(key, "_", String.Join("|", args.ToArray()));
      }

      WeakReference wr = null;
      if (s_WeakReferenceLookup.TryGetValue(key, out wr))
      {
        if (wr.IsAlive)
          return wr.Target;
        else
          s_WeakReferenceLookup.Remove(key);
      }

      object converter = (m_Arguments == null) ? Activator.CreateInstance(m_ConverterType) : Activator.CreateInstance(m_ConverterType, m_Arguments);
      s_WeakReferenceLookup.Add(key, new WeakReference(converter));

      return converter;
    }
    catch(MissingMethodException)
    {
      // constructor for the converter does not exist!
      throw;
    }
  }

}