C# :: Binding A String To A Textbox?

I have a textbox with XAML

<TextBox Grid.Row="0" Grid.Column="1"
HorizontalAlignment="Stretch" VerticalAlignment="Center"
Text="{Binding Path = EventDate, Mode=TwoWay}" />

And the Property

[edit]Note that auto formatting has edited onpropertychanged to all lowercase[/edit]
/// <summary>
/// Date that the event took place
/// </summary>
public string EventDate {

[code]....

In the constructor I have

EventDate = "Enter Date";

I have added a button

<Button Grid.Column="3" Content="Add Record" VerticalAlignment="Center" Click="AddRecordButtonclick"/>
public void AddRecordButtonclick(object sender, RoutedEventArgs e) {
Debug.WriteLine("Date value: " + EventDate);
}

What I am finding when I run this code is that when the Add Record button is clicked, the output displays, "Date value: Enter Date" regardless of what text I have in the textbox bound to EventDate.

Is there something obvious which I am missing with binding of a string to a textbox?

I've added this to the xaml, but the property is still not updating in the debug line

<TextBox Grid.Row="0" Grid.Column="1"
HorizontalAlignment="Stretch" VerticalAlignment="Center"
Text="{Binding Path=EventDate, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />