WPF将窗口标题绑定到ViewModel属性

问题描述

我试图将一个Window Title绑定到具有Title属性的ViewModel中。以下是MainWindow XAML：

I am trying to bind a Window Title to the ViewModel which has a Title property. Below is the MainWindow XAML:

<Window x:Class="MyProject.View.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:vm="clr-namespace:MyProject.ViewModel;assembly=MyProject.ViewModel"
        Title="{Binding Path=Title}" Height="350" Width="525" DataContext="{Binding Source={StaticResource mainWindowViewModel}}">
    <Window.Resources>
        <vm:MainWindow x:Key="mainWindowViewModel"/>
    </Window.Resources>

...

</Window>

当我尝试运行这个，我得到以下异常提供值System.Windows。 StaticResourceExtension'抛出异常，行号和位置指向DataContext属性，内部异常指出找不到名为mainWindowViewModel的资源。

When I try to run this, I get the following exception "Provide value on 'System.Windows.StaticResourceExtension' threw an exception. The line number and position point to the DataContext property, and the inner exception states "Cannot find resource named mainWindowViewModel.

下面是查看模型：

namespace MyProject.ViewModel
{
    public class MainWindow : INotifyPropertyChanged
    {
        #region Fields

        private const string TitlebarPrefixString = "My Project";
        private string title = TitlebarPrefixString;

        public string Title {
            get
            {
                return this.title;
            } // End getter
            set
            {
                this.title = value;
                OnPropertyChanged("Title");
            } // End setter
        } // End property

        protected virtual void OnPropertyChanged(string propertyName)
        {
            PropertyChangedEventHandler handler = PropertyChanged;
            if (handler != null)
            {
                handler(this, new PropertyChangedEventArgs(propertyName));
            } // End if
        } // End method


        public event PropertyChangedEventHandler PropertyChanged;

    } // End class
} // End namespace

我的理论是在试图将标题绑定到属性之后加载资源。当抛出异常时，Window的Resources属性为空。

My theory is that the resources are loaded after the attempt to bind the title to the property. When the exception is thrown, the Resources property for the Window is empty.

是否在Code Behind中设置DataContext的唯一解决方案？我可以让它工作，但我宁愿把它保留在XAML中。

Is the only solution to set the DataContext in the Code Behind? I can get this to work, but I would prefer to keep it in XAML.

推荐答案

你可以尝试设置 DataContext 使用属性元素语法：

You can try to set the DataContext using property element syntax:

<Window x:Class="MyProject.View.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:vm="clr-namespace:MyProject.ViewModel;assembly=MyProject.ViewModel"
    Title="{Binding Path=Title}" Height="350" Width="525">
<Window.Resources>
    <vm:MainWindow x:Key="mainWindowViewModel"/>
</Window.Resources>
<Window.DataContext>
  <StaticResourceExtension ResourceKey="mainWindowViewModel"/>
</Window.DataContext>

应该像xaml解析器一样执行 StaticResourceExtension 资源字典设置后。

That should work as the xaml parser will execute StaticResourceExtension after the resources dictionary is set.

但我认为甚至可以直接设置DataContext，而不将其声明为资源：

But i think maybe even better would be to set the DataContext directly, without declaring it as resource:

<Window x:Class="MyProject.View.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:vm="clr-namespace:MyProject.ViewModel;assembly=MyProject.ViewModel"
    Title="{Binding Path=Title}" Height="350" Width="525">
<Window.DataContext>
    <vm:MainWindow x:Key="mainWindowViewModel"/>
</Window.DataContext>

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