Silverlight Simple Drag And Drop / Or Browse View Model / MVVM File Upload Control

using System.Windows;
using System.Windows.Controls;
using System.Windows.Interactivity;
using System.Windows.Input;
using System.IO;

namespace OpenLightGroupBehaviors
{
    [System.ComponentModel.Description("Launches a Open File Dialog Box on Event Trigger")]
    public class OpenFileDialogBoxBehavior : TargetedTriggerAction<Button>
    {
        // Properties

        #region FileDialogDialogResultProperty

        public static readonly DependencyProperty FileDialogDialogResultProperty =
            DependencyProperty.Register("FileDialogDialogResultProperty",
            typeof(FileInfo), typeof(OpenFileDialogBoxBehavior), null);

        public FileInfo FileDialogDialogResult
        {
            get
            {
                return (FileInfo)base.GetValue(FileDialogDialogResultProperty);
            }
            set
            {
                base.SetValue(FileDialogDialogResultProperty, value);
            }
        }
        #endregion

        #region ParentControlProperty

        public static readonly DependencyProperty ParentControlProperty =
            DependencyProperty.Register("ParentControlProperty",
            typeof(object), typeof(OpenFileDialogBoxBehavior), null);

        public object ParentControl
        {
            get
            {
                return (object)base.GetValue(ParentControlProperty);
            }
            set
            {
                base.SetValue(ParentControlProperty, value);
            }
        }
        #endregion

        #region DialogFilterProperty

        public static readonly DependencyProperty DialogFilterProperty =
           DependencyProperty.Register("DialogFilter", typeof(string),
           typeof(OpenFileDialogBoxBehavior), null);

        public string DialogFilter
        {
            get
            {
                if (base.GetValue(DialogFilterProperty) == null)
                {
                    return
                        "JPEG Files (*.jpg;*.jpeg)|*.jpg;*.jpeg|"
                        + "Gif Files (*.gif)|*.gif|"
                        + "DOC Files (*.doc)|*.doc|"
                        + "DOCX Files (*.docx)|*.docx|"
                        + "XLS Files (*.xls)|*.xls|"
                        + "XLSX Files (*.xlsx)|*.xlsx|"
                        + "PDF Files (*.pdf)|*.pdf|"
                        + "PNG Files (*.png)|*.png|"
                        + "TXT Files (*.txt)|*.txt";
                }
                else
                {
                    return (string)base.GetValue(DialogFilterProperty);
                }
            }
            set
            {
                base.SetValue(DialogFilterProperty, value);
            }
        }

        #endregion

        #region SelectedFileNameProperty

        public static readonly DependencyProperty SelectedFileNameProperty =
           DependencyProperty.Register("SelectedFileName", typeof(string),
           typeof(OpenFileDialogBoxBehavior), null);

        public string SelectedFileName
        {
            get
            {
                return (string)base.GetValue(SelectedFileNameProperty);
            }
            set
            {
                base.SetValue(SelectedFileNameProperty, value);
            }
        }

        #endregion

        // Operations

        protected override void Invoke(object parameter)
        {
            OpenFileDialog objOpenFileDialog = new OpenFileDialog();
            objOpenFileDialog.Filter = DialogFilter;

            objOpenFileDialog.ShowDialog();

            // Set the file to the FileInfo property
            // this should be bound to the ViewModel by the designer
            FileDialogDialogResult = objOpenFileDialog.File;

            // Only proceed if a file was selected
            if (FileDialogDialogResult != null)
            {
                SelectedFileName = ShortenFileName(FileDialogDialogResult.Name);

                // Change to selected file Visual State
                VisualStateManager.GoToState((Control)ParentControl, "FileSelectedState", true);
            }
        }

        #region ShortenFileName
        private string ShortenFileName(string filename)
        {
            string strFilename = "...";

            if (filename.Length > 10)
            {
                strFilename = filename.Substring(0, 10) + " ...";
            }
            else
            {
                strFilename = filename;
            }

            return strFilename;
        } 
        #endregion
    }
}