How to bind a variable with a textblock

I was wondering how I would be able to bind a text block to a variable within my C# class.

Basically I have开发者_如何学Go a "cart" variable in my .cs file. Within that Cart class I have access to the different totals.

The following is what I have for binding, but it does not seem to bind to the variable...

<StackPanel
   Width="Auto"
   Height="Auto"
   Grid.ColumnSpan="2"
   Grid.Row="5"
   HorizontalAlignment="Right">
   <TextBlock
      Name="Subtotal"
      FontFamily="Resources/#Charlemagne Std"
      FontSize="20"
      Text="{Binding ElementName=cart, Path=SubTotal}">
   </TextBlock>
   <TextBlock
      Name="Tax"
      FontFamily="Resources/#Charlemagne Std"
      FontSize="20"
      Text="{Binding ElementName=cart, Path=Tax}">
   </TextBlock>
   <TextBlock
      Name="Total"
      FontFamily="Resources/#Charlemagne Std"
      FontSize="20"
      Text="{Binding ElementName=cart, Path=Total}">
   </TextBlock>
</StackPanel>

What is the correct way of doing it? Thanks again for the help!

If you further want the TextBoxes to update automatically when your cart class changes, your class must implement the INotifyPropertyChanged interface:

class Cart : INotifyPropertyChanged 
{
    // property changed event
    public event PropertyChangedEventHandler PropertyChanged;

    private int _subTotal;
    private int _total;
    private int _tax;

    private void OnPropertyChanged(String property)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(property));
        }
    }

    public int SubTotal
    {
        get
        {
            return _subTotal;
        }
        set
        {
            _subTotal = value;
            OnPropertyChanged("SubTotal");
        }
    }

    public int Total
    {
        get
        {
            return _total;
        }
        set
        {
            _total = value;
            OnPropertyChanged("Total");
        }
    }

    public int Tax
    {
        get
        {
            return _tax;
        }
        set
        {
            _tax = value;
            OnPropertyChanged("Tax");
        }
    }

}

ElementName in binding is used to reference other controls, not variables in code behind. To reference variables in code behind, you need to assign that variable to a Control's DataContext property.

Replace every occurrence of following line of code :

<TextBlock Name="Subtotal" FontFamily="Resources/#Charlemagne Std" FontSize="20" Text="{Binding ElementName=cart, Path=SubTotal}"></TextBlock>

with :

<TextBlock Name="Subtotal" FontFamily="Resources/#Charlemagne Std" FontSize="20" Text="{Binding Path=SubTotal}"></TextBlock>

And in your Window's constructor or Load event, write following code :

this.DataContext = cart;

Two solutions..

First solution:

Put the cart as DataSource in your code behind:

DataSource = cart;

And bind to it as follows:

{Binding Path=PropertyOfCart}

Second solution:

Bind to your root control with an ElementName binding, and get the cart through a property on this control:

Name your root/parent control where cart is a propery:

<UserControl .....snip..... x:Name="Root">

Bind to it like this:

{Binding ElementName=Root, Path=Cart.PropertyOfCart}

Please note that Cart must be a property of your UserControl, and not a field

You need to set your class as the data source for your form. See also this question.