如何使 WPF MVVM 绑定在 python.NET (Cpython) 中工作？

Question

我正在尝试使用 python.NET 将this IronPython WPF example 移植到 CPython。

在修复了一些已知问题（adding __namespace__ to the ViewModel class，使用Single Thread Apartment 并将 pyevent.py 的语法更新为 python3）后，我能够让窗口运行，但绑定被忽略：我可以在文本框中写入，但没有事件被触发，并且按钮不会触发 OnClick 方法。

这是完整的代码：

import clr
clr.AddReference(r'wpf\PresentationFramework')
clr.AddReference('PresentationCore')

from System.Windows.Markup import XamlReader
from System.Windows import Application, Window
from System.ComponentModel import INotifyPropertyChanged, PropertyChangedEventArgs
import pyevent
from System.Threading import Thread, ThreadStart, ApartmentState


XAML_str = """<Window xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Sync Paramanager" Height="180" Width="400">
    <StackPanel x:Name="DataPanel" Orientation="Horizontal">
        <Label Content="Size"/>
        <Label Content="{Binding size}"/>
        <TextBox x:Name="tbSize" Text="{Binding size, UpdateSourceTrigger=PropertyChanged}" />
        <Button x:Name="Button" Content="Set Initial Value"></Button>
    </StackPanel>
</Window>"""

class notify_property(property):

    def __init__(self, getter):
        def newgetter(slf):
            #return None when the property does not exist yet
            try:
                return getter(slf)
            except AttributeError:
                return None
        super().__init__(newgetter)

    def setter(self, setter):
        def newsetter(slf, newvalue):
            # do not change value if the new value is the same
            # trigger PropertyChanged event when value changes
            oldvalue = self.fget(slf)
            if oldvalue != newvalue:
                setter(slf, newvalue)
                slf.OnPropertyChanged(setter.__name__)
        return property(
            fget=self.fget,
            fset=newsetter,
            fdel=self.fdel,
            doc=self.__doc__)

class NotifyPropertyChangedBase(INotifyPropertyChanged):
    __namespace__ = "NotifyPropertyChangedBase"

    PropertyChanged = None

    def __init__(self):
        self.PropertyChanged, self._propertyChangedCaller = pyevent.make_event()

    def add_PropertyChanged(self, value):
        self.PropertyChanged += value

    def remove_PropertyChanged(self, value):
        self.PropertyChanged -= value

    def OnPropertyChanged(self, propertyName):
        if self.PropertyChanged is not None:
            self._propertyChangedCaller(self, PropertyChangedEventArgs(propertyName))

class ViewModel(NotifyPropertyChangedBase):
    __namespace__ = "WpfViewModel"

    def __init__(self):
        super(ViewModel, self).__init__()
        # must be string to two-way binding work correctly
        self.size = '10'

    @notify_property
    def size(self):
        return self._size

    @size.setter
    def size(self, value):
        self._size = value
        print(f'Size changed to {self.size}')

class TestWPF(object):

    def __init__(self):
        self._vm = ViewModel()
        self.root = XamlReader.Parse(XAML_str)
        self.DataPanel.DataContext = self._vm
        self.Button.Click += self.OnClick

    def OnClick(self, sender, event):
        # must be string to two-way binding work correctly
        self._vm.size = '10'

    def __getattr__(self, name):
        # provides easy access to XAML elements (e.g. self.Button)
        return self.root.FindName(name)


def main():
    tw = TestWPF()
    app = Application()
    app.Run(tw.root)


if __name__ == '__main__':
    thread = Thread(ThreadStart(main))
    thread.SetApartmentState(ApartmentState.STA)
    thread.Start()
    thread.Join()

似乎将 ModelView 分配给 DataPanel 的DataContext 不会触发任何绑定注册，但我不知道如何解决这个问题。

我错过了一些明显的东西吗？

Answer 1

不幸的是，pythonnet 不支持在 xaml 文件中定义绑定。