WF4 Custom activities for message mediation

//*****************************************************************************
//    Description.....WF4 Message Mediation Library
//                                
//    Author..........Roman Kiss, rkiss@pathcom.com
//    Copyright © 2009 ATZ Consulting Inc. (see included license.rtf file)         
//                        
//    Date Created:    07/07/09
//
//    Date        Modified By     Description
//-----------------------------------------------------------------------------
//    07/07/09    Roman Kiss     Initial Revision
//    10/10/12    Roman Kiss     Upadate 4.5
//*****************************************************************************
//
#region Namespaces
using System;
using System.Activities;
using System.Activities.Presentation.View;
using System.Linq;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
using System.Xml.Linq;
using Microsoft.VisualBasic.Activities;
//
using RKiss.MessageMediationActivityLibrary.Design.Dialogs.Forms;
#endregion

namespace RKiss.MessageMediationActivityLibrary.Design
{
    // Interaction logic for CreateMessageDesigner.xaml
    public partial class CreateMessageDesigner
    {
        public CreateMessageDesigner()
        {
            InitializeComponent();   
        }

        //protected override void OnModelItemChanged(object newItem)
        //{
        //    base.OnModelItemChanged(newItem);
        //    this.ExpandState = false;
        //}

        protected override void OnContentTemplateChanged(DataTemplate oldContentTemplate, DataTemplate newContentTemplate)
        {
            base.OnContentTemplateChanged(oldContentTemplate, newContentTemplate);
        }

        private void buttonMediator_Click(object sender, RoutedEventArgs e)
        {
            try
            {    
                // get the etb from dynamicly datatemplate
                ContentControl cc = e.Source as ContentControl;
                var sp = VisualTreeUtils.GetNamedChild<StackPanel>(cc.Parent, "stackPanel", 5);
                ExpressionTextBox expMediator = sp.Children[0] as ExpressionTextBox;
                if (expMediator == null)
                    throw new Exception("Internal error, ExpressionTextBox 'expMediator' doesn't exist in the content");
         
                var sourceUri = ModelItem.Properties.FirstOrDefault(p => p.Name == "SourceUri");
                string xmltext = expMediator.Expression == null ? string.Empty : (string)expMediator.Expression.Properties["ExpressionText"].ComputedValue;

                CreateMessageForm dialog = new CreateMessageForm(xmltext, sourceUri == null ? string.Empty : (string)sourceUri.ComputedValue);
                dialog.ShowDialog();
                if (dialog.DialogResult == System.Windows.Forms.DialogResult.OK)
                {
                    // set value for Mediator property
                    if (string.IsNullOrEmpty(dialog.XmlText) && expMediator.Expression != null)
                    {
                        ModelItem.Properties["Mediator"].SetValue(null);
                    }
                    else if (string.IsNullOrEmpty(dialog.XmlText) == false)
                    {                   
                        string xmltext2 = XDocument.Parse(dialog.XmlText, LoadOptions.None).ToString(SaveOptions.None);
                        Argument arg = Argument.Create(typeof(XElement), ArgumentDirection.In);
                        arg.Expression = new VisualBasicValue<XElement> { ExpressionText = xmltext2 };
                        ModelItem.Properties["Mediator"].SetValue(arg);
                    }

                    this.ModelItem.Properties["MessageVersion"].SetValue(dialog.MessageVersion); 
                    this.ModelItem.Properties["SourceUri"].SetValue(dialog.SourceUri);
                    ((RoutedCommand)DesignerView.CommitCommand).Execute(2, expMediator);
                }
            }
            catch (Exception ex)
            {
                System.Windows.MessageBox.Show(ex.Message);
            }
        }
    }
}