如何将可见性绑定到在用户控件中作为参数传递的元素？

Question

I have User control which looks like this:

public partial class TopBarUserControl : UserControl
{
    public System.Windows.Visibility menuVisibility { get; set; }

    public TopBarUserControl()
    {
        InitializeComponent();
    }
}

And I render it in my other page with:

<local:TopBarUserControl />

It works fine but I want to hide some part of my Control. So I pass the parameter to control with:

<local:TopBarUserControl menuVisibility="Collapsed" />

But I don't know how to make it works fine (hide my elements). What I have tried:

in xaml control:

Visibility="{Binding menuVisibility}"

or set it in code behind but I don't know where it should be setted.

Answer 1

Two things here, first you should ideally declare the property as a DependencyProperty , so you can bind against it and get automatic change notification to update the UI at the right time. Then, you need to correct the binding, so that it points to the property declared at the UserCoontrol level (as you wrote it, it binds to the DataContext , which may not be set.

Try this, in XAML:

<UserControl x:Class="WpfApplication1.TopBarUserControl"
             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"
             x:Name="MainControl">   <!--Give a XAML name to the whole control to bind to properties declared in code-behind-->

    <Menu Visibility="{Binding ElementName=MainControl, Path=MenuVisibility}"/>
</UserControl>

Notice the binding has an ElementName matching the x:Name at the control level. The convert your property to DependencyProperty :

using System.Windows;
using System.Windows.Controls;

namespace WpfApplication1
{
    public partial class TopBarUserControl : UserControl
    {
        public static readonly DependencyProperty MenuVisibilityProperty = DependencyProperty.Register("MenuVisibility", typeof(Visibility), typeof(TopBarUserControl), null);

        public Visibility MenuVisibility
        {
            get { return (Visibility)GetValue(MenuVisibilityProperty); }
            set { SetValue(MenuVisibilityProperty, value); }
        }

        public TopBarUserControl()
        {
            InitializeComponent();
        }
    }
}