wpf IViewFor Bind 扩展方法如何工作？
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How works IViewFor Bind extension method?
提问by Евгений Савин
Simple question, but I dons see solution. Or may be dont understand how Bind method works. The goal is two way binding between ViewModel and DataContext properties.
简单的问题，但我没有看到解决方案。或者可能不明白 Bind 方法是如何工作的。目标是 ViewModel 和 DataContext 属性之间的两种方式绑定。
public MainWindow()
{
InitializeComponent();
this.Bind(this, v => v.DataContext, v => v.ViewModel);
}
public static readonly DependencyProperty ViewModelProperty = DependencyProperty.Register(
"ViewModel", typeof (string), typeof (MainWindow));
public string ViewModel
{
get { return (string) GetValue(ViewModelProperty); }
set { SetValue(ViewModelProperty, value); }
}
when I set ViewModel property, I get InvalidCastException "System.String" to "WpfApplication1.MainWindow".
当我设置 ViewModel 属性时，我得到 InvalidCastException "System.String" 到 "WpfApplication1.MainWindow"。
But xaml binding works perfectly.
但是 xaml 绑定工作得很好。
<MainWindow
DataContext="{Binding RelativeSource={RelativeSource Self}, Path=ViewModel, Mode=TwoWay}" ...
full xaml.cs/xaml code is here http://pastebin.com/iCKeNS7R
完整的 xaml.cs/xaml 代码在这里http://pastebin.com/iCKeNS7R
Where I wrong ?
我错在哪里？
update:this code:
更新：此代码：
this.WhenAnyValue(v => v.ViewModel).BindTo(this, v => v.DataContext);
this.WhenAnyValue(v => v.DataContext).BindTo(this, v => v.ViewModel);
this.WhenAnyValue(v => v.ViewModel).BindTo(this, v => v.DataContext);
this.WhenAnyValue(v => v.DataContext).BindTo(this, v => v.ViewModel);
also works as expected
也按预期工作
update 2Question: Does this.Bind(viewModelParam, ...) ignore viewModelParam argument ??
更新 2问题：this.Bind(viewModelParam, ...) 是否忽略 viewModelParam 参数？？
example^ http://pastebin.com/e2aPaGNc
示例^ http://pastebin.com/e2aPaGNc
I bind to _otherViewModel, but when type text into textBox, ViewModel.StrProp changed, not _otherViewModel.
我绑定到 _otherViewModel，但是当在 textBox 中输入文本时，ViewModel.StrProp 发生了变化，而不是 _otherViewModel。
Does anybody know, how this.Bind work ??
有人知道 this.Bind 是如何工作的吗？
回答by Ana Betts
Binddoesn't work between ViewModel and DataContext because the types don't match (i.e. I could set DataContext to '4' and now it can't assign that to ViewModel).
Bind在 ViewModel 和 DataContext 之间不起作用，因为类型不匹配（即我可以将 DataContext 设置为“4”，现在它无法将其分配给 ViewModel）。
However, if you are using ReactiveUI bindings, you don't needDataContext at all, you should just use RxUI bindings everywhere. Please ignore the other answers on this thread that tell you how to do things the wrong way.
但是，如果您使用 ReactiveUI 绑定，则根本不需要DataContext，您应该在任何地方使用 RxUI 绑定。请忽略此线程上的其他答案，这些答案告诉您如何以错误的方式做事。
回答by Sagiv b.g
you can just bind the ViewModel via XAML:
您可以通过 XAML 绑定 ViewModel：
<Window x:Class="YourNameSpace.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:ViewModel="clr-namespace:YourNameSpace"
Title="MainWindow" Height="350" Width="525">
<Window.Resources>
<ViewModel:MainViewModel x:Key="MainViewModel"/>
</Window.Resources>
<Grid>
<TextBox Text="{Binding YourProperty, Mode=TwoWay, Source={StaticResource MainViewModel}, UpdateSourceTrigger=PropertyChanged}"/>
</Grid>
</Window>
your viewmodel should implement INotifyPropertyChanged.
您的视图模型应该实现 INotifyPropertyChanged。
public class MainViewModel : INotifyPropertyChanged
{
private string _yourProperty;
public string YourProperty
{
get { return _yourProperty; }
set { _yourProperty = value; OnPropertyChanged("YourProperty"); }
}
public MainViewModel()
{
_yourProperty = "Some string";
}
#region INotifyPropertyChanged Members
public event PropertyChangedEventHandler PropertyChanged = delegate { };
protected void OnPropertyChanged(string propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
#endregion
}
