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Posted 10 Sep 2012

Bindable Converter Parameter

, 2 Jul 2013 CPOL
A simple technique to achieve Bindable-ConverterParameter in WPF's XAML.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Reflection;
using System.Windows.Markup.Primitives;
using System.Diagnostics;
using System.Text.RegularExpressions;

namespace BindableConverterParameterTake2
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
        public MainWindow()
            this.DataContext = new MainViewModel();

        private void TextBox_Initialized(object item, EventArgs e)

        private void Grid_Initialized(object sender, EventArgs e)
            //get all  dependency-objects in logical-tree
            List<DependencyObject> AllLogicalTreeDependencyObjects=new List<DependencyObject>();

            FillAllLogicalTreeDependencyObjects(ref AllLogicalTreeDependencyObjects,sender as DependencyObject );

            //go over them
            foreach (var item in AllLogicalTreeDependencyObjects)
                MarkupObject markupObject = MarkupWriter.GetMarkupObjectFor(item);
                IEnumerable<DependencyProperty> MatchingDPs = markupObject.Properties.Select<MarkupProperty, DependencyProperty>
                    (mp => { return mp.DependencyProperty; }).Where
                    (dp =>
                            dp != null &&
                            BindingOperations.GetBinding(item, dp) != null &&
                            BindingOperations.GetBinding(item, dp).ConverterParameter != null &&
                            Regex.IsMatch(BindingOperations.GetBinding(item, dp).ConverterParameter.ToString(), "Binding");

                //for those who have Bindable converterParameter do the following:
                foreach (DependencyProperty dp in MatchingDPs)

                    Match m = Regex.Match(BindingOperations.GetBinding(item, dp).ConverterParameter.ToString(), "Binding Path=(?<path>[A-Za-z0-9]+)");
                    if (m != null)
                        string sConverterParameterBindingPath = m.Groups["path"].Value;

                        // get original binding
                        Binding bindingOrig = BindingOperations.GetBinding(item, dp);

                        //create set of attached properties to replase this ConverterParameter Binding
                        //give unique name by using dp's name:
                        DependencyProperty apBindingSource=null;

                        //(5.) another attached prop for two-way binding operations
                        DependencyProperty apIsSourceChanged = DependencyProperty.RegisterAttached(dp.Name + "IsSourceChanged", typeof(bool), item.GetType(), new PropertyMetadata(false));

                        // 1. attached-prop for the ConverterParameter-Binding
                        DependencyProperty apConverterParameterBindingSource = DependencyProperty.RegisterAttached(dp.Name + "ConverterParameterBindingSource", typeof(object), item.GetType(), new PropertyMetadata(null));
                        Binding bindingConverterParameterBindingSource = new Binding(sConverterParameterBindingPath);
                        BindingOperations.SetBinding(item, apConverterParameterBindingSource, bindingConverterParameterBindingSource);

                        // 2. attached-prop to hold the Converter Object
                        DependencyProperty apConverter = DependencyProperty.RegisterAttached(dp.Name + "Converter", typeof(IValueConverter), item.GetType(), new PropertyMetadata(null));
                        (item).SetValue(apConverter, bindingOrig.Converter);

                        //3. attached-prop to hold the evaluate result >>> will be binded to the original Binded dp
                        DependencyProperty apEvaluatedResult = DependencyProperty.RegisterAttached(dp.Name + "EvaluatedResult", typeof(object), item.GetType(), new PropertyMetadata(null, (s, edp) =>
                                if (!(bool)s.GetValue(apIsSourceChanged))
                                    // change didn't come from source>>> target got changed in two-way binding
                                    // change source via convert back
                                    object ret= (s.GetValue(apConverter) as IValueConverter).
                                        ConvertBack(edp.NewValue, null, s.GetValue(apConverterParameterBindingSource), null);
                                    s.SetValue(apBindingSource, ret);
                        Binding bindingOrigDpToEvaluatedResult = new Binding("(" + item.GetType().Name + "." + dp.Name + "EvaluatedResult)");
                        bindingOrigDpToEvaluatedResult.Source = item;
                        bindingOrigDpToEvaluatedResult.Mode =bindingOrig.Mode;
                        BindingOperations.SetBinding(item, dp, bindingOrigDpToEvaluatedResult);

                        // 4. attached-prop to replace the source binding - bind apBindingSource to the original source (instead of the original dp)
                        apBindingSource = DependencyProperty.RegisterAttached(dp.Name + "BindingSource", typeof(object), item.GetType(), new PropertyMetadata(null, (s, edp) =>
                                s.SetValue(apIsSourceChanged, true);
                                s.SetValue(apEvaluatedResult, (s.GetValue(apConverter) as IValueConverter).
                                    Convert(edp.NewValue, null, s.GetValue(apConverterParameterBindingSource), null));
                                s.SetValue(apIsSourceChanged, false);

                        Binding NewBindingToSource = new Binding(bindingOrig.Path.Path);
                        NewBindingToSource.Mode =bindingOrig.Mode;
                        BindingOperations.SetBinding(item, apBindingSource, NewBindingToSource); // reroute source to apBindingSource


        private void FillAllLogicalTreeDependencyObjects(ref List<DependencyObject> list,  DependencyObject depobj)
            List<DependencyObject> ret=new List<DependencyObject>();

                var children = LogicalTreeHelper.GetChildren(depobj);
                foreach (var item in children)
                    if (item is DependencyObject )
                        FillAllLogicalTreeDependencyObjects(ref list, item as DependencyObject );

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Software Developer (Senior) self employed
Israel Israel
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