[IronPython] DataBinding from IronPython Object to WPF Property

Steve Apiki sapiki at appropriatesolutions.com
Wed Aug 5 21:58:16 CEST 2009


I'm working with IronPython 2.6 Beta 1.

I have the following Python class:

class Person(object):
    def __init__(self, name):
        self.name = name

I'd like to be able to bind the name property of an instance of this class to a WPF textbox control.

I can do this easily enough either in XAML or in code. When the application starts, the textbox displays the person's name as expected.

However, if I make changes to the name, say, in response to a button click:

def button_click(sender, args):
    a_person.name += ", jr."

I don't see these changes reflected in the textbox.

I can make this work by calling UpdateTarget on the binding expression explicitly:

    exp = BindingOperations.GetBindingExpression(textbox, TextBox.TextProperty)

but I had thought this would work without the explicit step, since it appears that IronPython supports INotifyPropertyChange.

Two questions:

(1) Is it possible to get databinding to work this way without having to explicity UpdateTarget?

(2) Say instead of the click handler above, we had:

def button_click(sender, args):
    global a_person
    a_person = Person("Fred")

In this case, the textbox remains bound to the first Person (which is no longer accessible from Python). Is there any way to get the binding to re-sync to the new object, short of setting a completely new binding to Person("Fred") in code?

Full example follows.




import clr
clr.AddReferenceByName("PresentationFramework, Version=, Culture=neutral, PublicKeyToken=31bf3856ad364e35")
clr.AddReferenceByName("PresentationCore, Version=, Culture=neutral, PublicKeyToken=31bf3856ad364e35")

from System.Windows import Application, Window
from System.Windows.Controls import StackPanel, Button, TextBox
from System.Windows.Data import Binding, BindingMode, BindingOperations
class Person(object):
    def __init__(self, name):
        self.name = name
a_person = Person("Al")

button = Button()
button.Content = "Test"

textbox = TextBox()
textbox.DataContext = a_person
binding = Binding("name")
binding.Source = a_person
binding.Mode = BindingMode.OneWay
textbox.SetBinding(TextBox.TextProperty, binding)

def button_click(sender, args):
    """ click handler """
    a_person.name += ", jr."

    # if you uncomment the following, the textbox is updated
    # with each button click. If you don't, the text never changes.
    #exp = BindingOperations.GetBindingExpression(textbox, TextBox.TextProperty)
button.Click += button_click

window = Window()
stackpanel = StackPanel()
window.Content = stackpanel



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