bind dependency property from custom class to UI - wpf

Question

have tried for almost a hole week to find how to bind my dependency property that is in a custom class (Elements) to a simple text box,
Text inside textbox must change every time when i send particular data, this is happening for the first time only,after that, textbox want be updated ??
i have tried every single example but i could not reach my goal, here is my code :
for the class where the depency object created :
public class Elements : DependencyObject
{
public static DependencyProperty TextDataProperty = DependencyProperty.Register
(
"TextData",
typeof(string),
typeof(Elements),
new FrameworkPropertyMetadata("", FrameworkPropertyMetadataOptions.AffectsRender)
);
public string TextData
{
get
{
return (string)GetValue(TextDataProperty);
}
set
{
SetValue(TextDataProperty, value);
}
}
public void UpdateText(string sdata)
{
TextData = sdata;
}
}
i have refere to this class in xaml like so
xmlns:local="clr-namespace:WpfApplication1"
and to use it :
<Window.Resources>
<local:Elements x:Key="myElements" ></local:Elements>
</Window.Resources>
the text box that need to be updated is binded to the custom class like this :
<TextBox
Height="23"
HorizontalAlignment="Left"
Margin="12,61,0,0"
Name="textBox1"
VerticalAlignment="Top"
Width="237"
Text="{Binding TextData, Source={StaticResource myElements}}"
/>
what im doing wrong ?? can someone help please

Answer 1

From your comment: You are creating a new Elements object in
Elements _elements = new Elements();
_elements.UpdateText(textBox2.Text);
This is not the object that is used for the binding in
Text="{Binding TextData, Source={StaticResource myElements}}"
Change your code so that it accesses the object from the Resources:
var elements = (Elements)Resources["myElements"];
elements.UpdateText(textBox2.Text);
Then you should replace the TextBox by a TextBlock, because you only want to display text, but do not want the user to edit it.
You should also take a look at the MVVM design pattern and how it is used in WPF. There are plenty of online resources available.