c# - 使 AvalonEdit MVVM 兼容

Question

我正在努力使 Avalon MVVM 在我的 WPF 应用程序中兼容。通过谷歌搜索，我发现 AvalonEdit is not MVVM friendly我需要通过创建一个从 TextEditor 派生的类然后添加必要的依赖属性来导出 AvalonEdit 的状态。恐怕我对 Herr Grunwald 的回答很迷茫 here :

If you really need to export the state of the editor using MVVM, then I suggest you create a class deriving from TextEditor which adds the necessary dependency properties and synchronizes them with the actual properties in AvalonEdit.

有没有人有关于如何实现这一目标的示例或好的建议？

Answer 1

Herr Grunwald 正在谈论用 dependency properties 包装 TextEditor 属性，以便您可以绑定(bind)到它们。基本思路是这样的(例如使用 CaretOffset 属性):

修改的TextEditor类

public class MvvmTextEditor : TextEditor, INotifyPropertyChanged
{
    public static DependencyProperty CaretOffsetProperty = 
        DependencyProperty.Register("CaretOffset", typeof(int), typeof(MvvmTextEditor),
        // binding changed callback: set value of underlying property
        new PropertyMetadata((obj, args) =>
        {
            MvvmTextEditor target = (MvvmTextEditor)obj;
            target.CaretOffset = (int)args.NewValue;
        })
    );

    public new string Text
    {
        get { return base.Text; }
        set { base.Text = value; }
    }

    public new int CaretOffset
    {
        get { return base.CaretOffset; }
        set { base.CaretOffset = value; }
    }

    public int Length { get { return base.Text.Length; } }

    protected override void OnTextChanged(EventArgs e)
    {
        RaisePropertyChanged("Length");
        base.OnTextChanged(e);
    }

    public event PropertyChangedEventHandler PropertyChanged;
    public void RaisePropertyChanged(string info)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(info));
        }
    }
}

既然 CaretOffset 已经被包装在 DependencyProperty 中，您可以将它绑定(bind)到一个属性，比如 View 模型中的 Offset。例如，将 Slider 控件的值绑定(bind)到相同的 View 模型属性 Offset，并看到当您移动 Slider 时，Avalon 编辑器的光标位置得到更新:

测试 XAML

<Window x:Class="AvalonDemo.TestWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:avalonEdit="http://icsharpcode.net/sharpdevelop/avalonedit"
    xmlns:avalonExt="clr-namespace:WpfTest.AvalonExt"
    DataContext="{Binding RelativeSource={RelativeSource Self},Path=ViewModel}">
  <StackPanel>
    <avalonExt:MvvmTextEditor Text="Hello World" CaretOffset="{Binding Offset}" x:Name="editor" />
    <Slider Minimum="0" Maximum="{Binding ElementName=editor,Path=Length,Mode=OneWay}" 
        Value="{Binding Offset}" />
    <TextBlock Text="{Binding Path=Offset,StringFormat='Caret Position is {0}'}" />
    <TextBlock Text="{Binding Path=Length,ElementName=editor,StringFormat='Length is {0}'}" />
  </StackPanel>
</Window>

测试代码隐藏

namespace AvalonDemo
{
    public partial class TestWindow : Window
    {
        public AvalonTestModel ViewModel { get; set; }

        public TestWindow()
        {
            ViewModel = new AvalonTestModel();
            InitializeComponent();
        }
    }
}

测试 View 模型

public class AvalonTestModel : INotifyPropertyChanged
{
    private int _offset;

    public int Offset 
    { 
        get { return _offset; } 
        set 
        { 
            _offset = value; 
            RaisePropertyChanged("Offset"); 
        } 
    }

    public event PropertyChangedEventHandler PropertyChanged;
    public void RaisePropertyChanged(string info)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(info));
        }
    }
}