Question

这是these two个问题的后续跟进。我有一个自定义用户控件，旨在允许用户调整颜色A，R，G和B通道：

enter image description here

这些滑块中的每一个都通过Color.FromScRgb方法控制颜色的一个方面。

每个滑块从0到1运行。

我已经实现了一个类来处理来自控件的输入 - 一个Color View Model类：

public class ColorViewModel : INotifyPropertyChanged {

    public event PropertyChangedEventHandler PropertyChanged;

    private Color _Color = Colors.Black;

    public double A {
        get { return this.Color.ScA; }
        set {
            this._Color.ScA = ( float )value;
            if ( this.PropertyChanged != null ) {
                this.PropertyChanged( this, new PropertyChangedEventArgs( "A" ) );
                this.PropertyChanged( this, new PropertyChangedEventArgs( "Color" ) );
            }
        }
    }
    public double R {
        get { return this.Color.ScR; }
        set {
            this._Color.ScR = ( float )value;
            if ( this.PropertyChanged != null ) {
                this.PropertyChanged( this, new PropertyChangedEventArgs( "R" ) );
                this.PropertyChanged( this, new PropertyChangedEventArgs( "Red" ) );
                this.PropertyChanged( this, new PropertyChangedEventArgs( "Color" ) );
            }
        }
    }
    public double G {
        get { return this.Color.ScG; }
        set {
            this._Color.ScG = ( float )value;
            if ( this.PropertyChanged != null ) {
                this.PropertyChanged( this, new PropertyChangedEventArgs( "G" ) );
                this.PropertyChanged( this, new PropertyChangedEventArgs( "Green" ) );
                this.PropertyChanged( this, new PropertyChangedEventArgs( "Color" ) );
            }
        }
    }
    public double B {
        get { return this._Color.ScB; }
        set {
            this._Color.ScB = ( float )value;
            if ( this.PropertyChanged != null ) {
                this.PropertyChanged( this, new PropertyChangedEventArgs( "B" ) );
                this.PropertyChanged( this, new PropertyChangedEventArgs( "Blue" ) );
                this.PropertyChanged( this, new PropertyChangedEventArgs( "Color" ) );
            }
        }
    }

    public Color Color {
        get { return this._Color; }
        set {
            this._Color = value;
            if ( this.PropertyChanged != null )
                this.AllChanged( );
        }
    }
    public Color Red { get { return Color.FromScRgb( 1.0F, ( float )this.R, 0.0F, 0.0F ); } }
    public Color Green { get { return Color.FromScRgb( 1.0F, 0.0F, ( float )this.G, 0.0F ); } }
    public Color Blue { get { return Color.FromScRgb( 1.0F, 0.0F, 0.0F, ( float )this.B ); } }

    private void AllChanged( ) {
        this.PropertyChanged( this, new PropertyChangedEventArgs( "A" ) );
        this.PropertyChanged( this, new PropertyChangedEventArgs( "R" ) );
        this.PropertyChanged( this, new PropertyChangedEventArgs( "G" ) );
        this.PropertyChanged( this, new PropertyChangedEventArgs( "B" ) );
        this.PropertyChanged( this, new PropertyChangedEventArgs( "Red" ) );
        this.PropertyChanged( this, new PropertyChangedEventArgs( "Green" ) );
        this.PropertyChanged( this, new PropertyChangedEventArgs( "Blue" ) );
        this.PropertyChanged( this, new PropertyChangedEventArgs( "Color" ) );
    }
}

通讯效果很好 - 每当我调整控制设置时，我都能看到它反映在CVM课程中。这很好，但它对我没有帮助，因为我需要一种从CVM类访问颜色的方法。我使用CVM类的一个实例作为控件的数据上下文，然后我尝试将Control中的自定义属性绑定到控件数据上下文，但它似乎没有工作：

以下是XAML的一部分：

<UserControl
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
    xmlns:Components="clr-namespace:WPFTools.Components"
    xmlns:Controls="clr-namespace:WPFTools.Controls"
    x:Class="WPFTools.Controls.ColorDefiner"
    mc:Ignorable="d"
    Width="120" Height="109.25" FontFamily="Arial" FontWeight="Bold">
    <UserControl.DataContext>
        <Controls:ColorViewModel/>
    </UserControl.DataContext>

这是控制类代码（如果有人认为有必要，我可以提供XAML，但是现在我会把它留下来 - 因为它非常详细） -

public partial class ColorDefiner : UserControl {

    public static readonly DependencyProperty
        _Color = DependencyProperty.Register( "Color", typeof( Color ), typeof( ColorDefiner ) );

    public Color Color {
        get { return ( Color )this.GetValue( ColorDefiner._Color ); }
        set { this.SetValue( ColorDefiner._Color, value ); }
    }

    private ColorViewModel CVM { get { return this.DataContext as ColorViewModel; } }

    public ColorDefiner( ) {
        InitializeComponent( );
        //There is no error here, but it seems that the color is not being set in the Color property of this control!
        Binding B = new Binding( "Color" ) { Source = this.DataContext, Mode = BindingMode.TwoWay };
        this.SetBinding( ColorDefiner._Color, B );
    }
}

我在Set Color属性上设置了一个断点，但是当我调整其中一个滑块时它没有被击中。

我在这里正确实施MVVM吗？为什么CVM没有更新ColorDefiner颜色属性？

修改

有人建议我可以绑定到DataContextChanged事件 - 这不起作用。

public ColorDefiner( ) {
    this.DataContextChanged += ( S, E ) => {
        Binding B = new Binding( "Color" ) { Source = this.DataContext, Mode = BindingMode.TwoWay };
        this.SetBinding( ColorDefiner._Color, B );
    };
    InitializeComponent( );
}

我尝试使用InitializeComponent下面的事件，但调用顺序错误，事件从未触发。以这种方式，事件被触发，但CVM仍未设置依赖项属性。也;我不认为这是问题，就好像它是，然后DataContext将为null并且应该抛出异常（我认为）。

MVVM属性不更新它已在Code Behind中绑定的依赖项属性

修改

0 个答案: