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
//
//*****************************************************************************
//
#region Namespaces
using System;
using System.Activities;
using System.Activities.Presentation.Converters;
using System.Activities.Presentation.Model;
using System.Activities.Presentation.PropertyEditing;
using System.Linq;
using System.Windows;
using System.Xml.Linq;
using Microsoft.VisualBasic.Activities;
using RKiss.MessageMediationActivityLibrary.Design.Dialogs.Forms;
#endregion

namespace RKiss.MessageMediationActivityLibrary.Design.Editors
{

    public class MessageMediationEditor : XmlValueExpressionEditor
    {
        public override void ShowDialog(PropertyValue propertyValue, IInputElement commandSource)
        {
            try
            {
                if (propertyValue != null)
                {
                    ModelPropertyEntryToOwnerActivityConverter converter = new ModelPropertyEntryToOwnerActivityConverter();
                    ModelItem activity = (ModelItem)converter.Convert(propertyValue.ParentProperty, typeof(ModelItem), false, null);
                    ModelItem item2 = (ModelItem)converter.Convert(propertyValue.ParentProperty, typeof(ModelItem), true, null);

                    // properties
                    var qSourceUri = item2.Properties.FirstOrDefault(p => p.Name == "SourceUri");

                    // values
                    string sourceUri = qSourceUri == null ? string.Empty : qSourceUri.ComputedValue as string;
                    string xmltext = propertyValue.Value != null ? ((propertyValue.Value as InArgument<XElement>).Expression as VisualBasicValue<XElement>).ExpressionText : string.Empty;

                    CreateMessageForm dialog = new CreateMessageForm(xmltext, sourceUri);
                    dialog.ShowDialog();
                    if (dialog.DialogResult == System.Windows.Forms.DialogResult.OK)
                    {
                        item2.Properties["SourceUri"].SetValue(dialog.SourceUri);
                        if (string.IsNullOrEmpty(dialog.XmlText))
                            propertyValue.Value = null;
                        else
                        {
                            var vbv = new VisualBasicValue<XElement>(dialog.XmlText);
                            propertyValue.Value = new InArgument<XElement>(vbv);
                        }
                    }
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }
    }
}