Adding a Timer Class to a project.

Question

I added a new class.cs to my project. Very simple for some.
I have textbox that I want to populate the date and time. The code is complete works fine. I want to stay organize, I don't really want to add anymore code to the MainWindow.cs. I'm having trouble fomatting the Timer.cs to bind with textbox on the MainWindow.
 
The XAML code is

 
<TextBox Height="41" Text="{Binding CurrentDateTime}"

 
 
The  Timer.cs is the following:

 
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace WpfApplication9
{
public partial class Timer 
{
private Timer clockTimer;
public Timer();
{

clockTimer = new Timer(1000);
clockTimer.Elapsed += new ElapsedEventHandler(clockTimer_Elapsed);
clockTimer.Start();
DataContext = this;
}
void clockTimer_Elapsed(object sender, ElapsedEventArgs e)
{
Dispatcher.BeginInvoke(new Action(UpdateCurrentDateTime));
}
 
 
public string CurrentDateTime
{
get { return (string)GetValue(CurrentDateTimeProperty); }
set { SetValue(CurrentDateTimeProperty, value); }
}
public static readonly DependencyProperty CurrentDateTimeProperty =
DependencyProperty.Register("CurrentDateTime", typeof(string), typeof(Mainwindow), new UIPropertyMetadata(string.Empty));
private void UpdateCurrentDateTime()
{
CurrentDateTime = DateTime.Now.ToString("MM/dd/yyyy hh:mm:ss");
}
}
 

 
This is my first time I'm trying to establish a class(.cs) in a project. any help would be great
 
Thanks