WPF

WPF stands for Windows Presentation Foundation.

Microsoft describes WPF as follows:

Windows Presentation Foundation (WPF) provides developers with a unified programming model for building rich Windows smart client user experiences that incorporate UI, media, and documents. [1]

Windows Presentation Foundation (WPF) is a next-generation presentation system for building Windows client applications with visually stunning user experiences. With WPF, you can create a wide range of both standalone and browser-hosted applications. [2]

WPF is part of .NET Framework and is only available currently on Windows platforms that can run .NET Framework 3 or higher.

WPF is not just for developers. It is designed to allow developers and designers to work together. Developers usually interface with WPF through Visual Studio, while designer interface with WPF using Expression Blend.


A FileTextBox control in WPF

Have you ever wanted a text file to be displayed in readonly fashion in a WPF window? Perhaps you have a log file and you want the UI to stay synced with the log updates to the file? Maybe you simply want to write a WPF version of WinTail?

Well, I just wrote a control in which you can set file path to a DependencyProperty and the UI will stay up to date. I created a child of TextBox called FileTextBox and implemented FileSystemWatcher.

Update: 6/16/2014 – Added AutoScroll.

using System;
using System.IO;
using System.Windows;
using System.Windows.Controls;

namespace WpfSharp.UserControls
{
    public class FileTextBox : TextBox
    {
        #region Private fields
        private bool _ChangedHandlerAdded;
        private bool _CreatedHandlerAdded;
        private bool _DeletedHandlerAdded;
        private bool _RenameHandlerAdded;
        #endregion

        #region constructor
        public FileTextBox()
        {
            AcceptsReturn = true;
            IsReadOnly = true;
            AutoScroll = true;
        }
        #endregion

        #region Properties
        /// <summary>
        /// If true, the FileTextBox will always scroll to the end when updated.
        /// </summary>
        public bool AutoScroll { get; set; }
        #endregion

        #region File Dependency Property
        public string File
        {
            get { return (string)GetValue(FileProperty); }
            set { SetValue(FileProperty, value); }
        }

        // Using a DependencyProperty as the backing store for File.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty FileProperty =
            DependencyProperty.Register("File", typeof(string), typeof(FileTextBox), new FrameworkPropertyMetadata(OnFilePropertyChanged));

        private static void OnFilePropertyChanged(DependencyObject sender, DependencyPropertyChangedEventArgs args)
        {
            var ftb = sender as FileTextBox;
            if (ftb == null || args.NewValue == null || string.IsNullOrWhiteSpace(args.NewValue.ToString()))
            {
                return;
            }
            var dir = GetDirectory(ref args);
            if (!string.IsNullOrWhiteSpace(dir) && Directory.Exists(dir))
            {
                ftb.Watcher.Path = Path.GetDirectoryName(args.NewValue.ToString());
                ftb.Watcher.Filter = Path.GetFileName(args.NewValue.ToString());
                ftb.AddEvents();
                ftb.Watcher.EnableRaisingEvents = true;
                ftb.UpdateFile();
            }
            else
            {
                ftb.Text = string.Empty;
            }
        }

        private static string GetDirectory(ref DependencyPropertyChangedEventArgs args)
        {
            try
            {
                return Path.GetDirectoryName(args.NewValue.ToString());
            }
            catch (Exception)
            {
                return null;
            }
        }
        #endregion

        private FileSystemWatcher Watcher
        {
            get { return _Watcher ?? (_Watcher = BuildWatcher()); }
        } private FileSystemWatcher _Watcher;

        private FileSystemWatcher BuildWatcher()
        {
            var watcher = new FileSystemWatcher { NotifyFilter = NotifyFilters.LastAccess | NotifyFilters.LastWrite | NotifyFilters.FileName | NotifyFilters.DirectoryName };
            return watcher;
        }

        public void OnFileDeleted(object sender, FileSystemEventArgs e)
        {
            Dispatcher.Invoke(UpdateFile);
        }

        public void OnFileChanged(object sender, FileSystemEventArgs e)
        {
            Dispatcher.Invoke(UpdateFile);
        }

        public void OnFileCreated(object sender, FileSystemEventArgs e)
        {
            Dispatcher.Invoke(() =>
            {
                UpdateFile();
                EnableRaiseEvents();
            });
        }

        public void OnFileRenamed(object sender, RenamedEventArgs e)
        {
            Dispatcher.Invoke(UpdateFile);
        }

        private void EnableRaiseEvents()
        {
            Dispatcher.Invoke(() =>
            {
                if (!Watcher.EnableRaisingEvents)
                    Watcher.EnableRaisingEvents = true;
            });
        }

        private void UpdateFile()
        {
            if (!System.IO.File.Exists(File))
            {

                Text = string.Empty;
                return;
            }
            using (var fs = new FileStream(File, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
            {
                using (var sr = new StreamReader(fs))
                {
                    Text = sr.ReadToEnd();
                    if (AutoScroll)
                        ScrollToEnd();
                }
            }
        }

        private void AddEvents()
        {
            if (!_CreatedHandlerAdded)
            {
                Watcher.Created += OnFileCreated;
                _CreatedHandlerAdded = true;
            }
            if (!_ChangedHandlerAdded)
            {
                Watcher.Changed += OnFileChanged;
                _ChangedHandlerAdded = true;
            }
            if (!_DeletedHandlerAdded)
            {
                Watcher.Deleted += OnFileDeleted;
                _DeletedHandlerAdded = true;
            }
            if (!_RenameHandlerAdded)
            {
                Watcher.Renamed += OnFileRenamed;
                _RenameHandlerAdded = true;
            }
        }
    }
}

As always, feedback is appreciated.