Binding a Textbox to a property in WPF

Question

I have a Textbox in a User Control i'm trying to update from my main application but when I set the textbox.Text property it doesnt display the new value (even though textbos.Text contains the correct data). I am trying to bind my text box to a property to get around this but I dont know how, here is my code -

MainWindow.xaml.cs

outputPanel.Text = outputText;

OutputPanel.xaml

<TextBox x:Name="textbox" 
             AcceptsReturn="True" 
             ScrollViewer.VerticalScrollBarVisibility="Visible"
             Text="{Binding <!--?????--> }"/>  <!-- I want to bind this to the Text Propert in OutputPanel.xmal.cs -->                               

OutputPanel.xaml.cs

 namespace Controls
{
public partial class OutputPanel : UserControl
{
    private string text;

    public TextBox Textbox
    {
        get {return textbox;}
    }

    public string Text
    {
        get { return text; }
        set { text = value; }
    }

    public OutputPanel()
    {
        InitializeComponent();
        Text = "test";
        textbox.Text = Text;
    }

}

}

Solution 1

You have to set a DataContext in some parent of the TextBox, for example:

<UserControl Name="panel" DataContext="{Binding ElementName=panel}">...

Then the binding will be:

Text="{Binding Text}"

And you shouldn't need this - referring to specific elements from code behind is usually bad practice:

public TextBox Textbox
{
    get {return textbox;}
}

Solution 2

I hope this example will help you.

1) Create UserControl.

2) Add to XAML <TextBlock Text="{Binding Path=DataContext.HeaderText}"></TextBlock>

3) In the code behind of that UserControl add

public partial class MyUserControl: UserControl

    {
        public string HeaderText { set; get; } // Add this line

        public MyUserControl()
        {
            InitializeComponent();

            DataContext = this; // And add this line
        }
    }

4) Outside of the control and let's say in the MainWindow Load event you have to do like

this.gdMain = new MyUserControl{ HeaderText = "YES" };