如何從另一個控件中綁定到自定義控件按鈕可見性

Question

我有一個自定義控件，它有一個按鈕：

<UserControl x:Class="Gambit.Views.FileSelectionControl"
    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" 
    SnapsToDevicePixels="True" 
    mc:Ignorable="d">
    ...
    <Button Content="Load" 
            Margin="5,5,5,5" 
            Height="22" 
            Width="70" 
            IsDefault="True" 
            IsEnabled="{Binding SelectedFileExists}" 
            AttachedCommand:CommandBehavior.Event="Click" 
            AttachedCommand:CommandBehavior.Command="{Binding CloseDialogCommand}"/>
    ...
</UserControl>

我希望在另一個控件中包含此控件，但我想在主機控件中設置Load按鈕的可見性; 就像是

<UserControl x:Class="Gambit.Views.SomeOtherControl"
    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" 
    SnapsToDevicePixels="True" 
    mc:Ignorable="d">
    ...
    <GroupBox Header="Select Test Data">
        <Views:FileSelectionControl <Here Set the Load Button Visibility>/>
    </GroupBox>
    ...
</UserControl>

其中<Here Set the Load Button Visibility>顯示我想要設置控件可見性的位置。 如何完成[不破壞MVVM模式]？

謝謝你的時間。

Answer 1

您可以在UserControl創建DependencyProperty ：

public partial class SomeView : UserControl
{
    ...

    public static DependencyProperty ButtonVisibilityProperty = DependencyProperty.Register("ButtonVisibility", typeof(Visibility), typeof(SomeView));

    public Visibility ButtonVisibility
    {
        get { return (Visibility)GetValue(ButtonVisibilityProperty); }
        set { SetValue(ButtonVisibilityProperty, value); }
    }
}

將它綁定到Button.Visibility ：

<UserControl x:Class="WpfApplication2.SomeView"
             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" 
             mc:Ignorable="d">
    <Button Visibility="{Binding RelativeSource={RelativeSource AncestorType={x:Type UserControl}}, Path=ButtonVisibility}" Content="My Button"/>
</UserControl>

然后您可以從外部控制Visibility ，如下所示：

<local:SomeView ButtonVisibility="Collapsed"/>

因為它是DependencyProperty你也可以使用Binding

Answer 2

您好，只需在UserControl1中創建一個bool或Visibility Type屬性，並將其設置為Usercontrol2之類

UserControl1 xaml

<UserControl x:Class="WpfApplication4.UserControl1"
         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" 
         mc:Ignorable="d" 
         d:DesignHeight="300" d:DesignWidth="300">
<Grid>
    <Button x:Name="Loadbutton" Content="load"/>
</Grid>

xaml.cs

 public UserControl1()
    {
        InitializeComponent();
    }

    bool showLoadButton;
    public bool ShowLoadButton
    {
        get { return showLoadButton; }
        set
        {
            showLoadButton = value;
            if (showLoadButton)
                Loadbutton.Visibility = Visibility.Visible;
            else
                Loadbutton.Visibility = Visibility.Collapsed;
        }

    }

UserControl2設置ShowLoadButton True或false

<UserControl x:Class="WpfApplication4.UserControl2"
         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:local="clr-namespace:WpfApplication4"
         mc:Ignorable="d" 
         d:DesignHeight="300" d:DesignWidth="300">
<Grid>
    <local:UserControl1 ShowLoadButton="True"/>
</Grid>

Answer 3

如果您不想在UserControl定義屬性，您可以始終創建附加的依賴項屬性，並且可以在公共名稱空間下的單獨類中聲明它。

像這樣的東西：

MainWindow.xaml

<local:TestUserControl AttachedProperties:ButtonExt.Visibility="Visible" />

TestUserControl.xaml

<Button Visibility="{Binding RelativeSource={RelativeSource AncestorType={x:Type UserControl}}, 
                             Path=(AttachedProperties:ButtonExt.Visibility)}"
        Content="TestButton" />

附屬物定義：

public static class ButtonExt
{
    public static readonly DependencyProperty VisibilityProperty;

    public static void SetVisibility(DependencyObject DepObject, Visibility value)
    {
        DepObject.SetValue(VisibilityProperty, value);
    }

    public static Visibility GetVisibility(DependencyObject DepObject)
    {
        return (Visibility)DepObject.GetValue(VisibilityProperty);
    }

    static ButtonExt()
    {
        PropertyMetadata VisibiltyPropertyMetadata = new PropertyMetadata(Visibility.Collapsed);

        VisibilityProperty = DependencyProperty.RegisterAttached("Visibility",
                                                            typeof(Visibility),
                                                            typeof(ButtonExt),
                                                            VisibiltyPropertyMetadata);
    }
}

Some notes about code-behind in MVVM

我同意@dkozl，他的例子並沒有違反MVVM的原則，在某些情況下，代碼存在於View ，例如（個人而言，我總是試圖避免代碼隱藏）：

• 安裝DataContext 。

• 使用不同的模式，如Mediator，Proxy等。

• 確定僅與View相關的屬性和行為（如您的情況）。

當您使用代碼隱藏時最重要的是，通過ViewModel可能發生所有操作，即在ViewModel包含所有邏輯，例如，在View click事件中，調用ViewModel的函數。

有關代碼隱藏的更多信息，請參閱最近問題的答案：

WPF MVVM代碼背后