WPF:在XAML中设置ItemSource与代码隐藏

Question

由于这是WPF,它可能看起来像很多代码,但不要害怕,问题很简单!

我有以下XAML:

<Window
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:hax="clr-namespace:hax" x:Class="hax.MainWindow"
    x:Name="Window" Title="Haxalot" Width="640" Height="280">

    <Grid x:Name="LayoutRoot">
        <ListView ItemsSource="{Binding AllRoles}" Name="Hello">
            <ListView.View>
                <GridView>
                    <GridViewColumn Header="Name"
                       DisplayMemberBinding="{Binding Path=FullName}"/>
                    <GridViewColumn Header="Role"
                       DisplayMemberBinding="{Binding Path=RoleDescription}"/>
                </GridView>
            </ListView.View>
        </ListView> 
    </Grid>
</Window>

我有这个代码隐藏:

using System.Collections.ObjectModel;
using System.Windows;

namespace hax
{

    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {

        public ObservableCollection<Role> AllRoles { get { return m_AllRoles; } set { m_AllRoles = value; } }
        private ObservableCollection<Role> m_AllRoles = new ObservableCollection<Role>();

        public MainWindow()
        {
            this.InitializeComponent();

            AllRoles.Add(new Role("John", "Manager"));
            AllRoles.Add(new Role("Anne", "Trainee"));
            // Hello.ItemsSource = AllRoles; // NOTE THIS ONE!
        }
    }
}

如果我将声明留下Hello.ItemSource = AllRoles注释,则网格不显示任何内容.当我把它放回去时,它会显示正确的东西.为什么是这样？

Answer 1

这个:

<ListView ItemsSource="{Binding AllRoles}" Name="Hello">

表示"绑定ItemsSource到属性this.DataContext.AllRoles",其中this是当前元素.

Hello.ItemsSource = AllRoles;

意味着"绑定ItemsSource到一个ObservableCollection<T>完整的角色",它直接做你原本想做的事情.

在xaml中有很多方法可以做到这一点.这是一个:

public partial class MainWindow : Window
{
    public MainWindow()
    {
        this.InitializeComponent();
        var allRoles = new ObservableCollection<Role>()
        allRoles.Add(new Role("John", "Manager"));
        allRoles.Add(new Role("Anne", "Trainee"));
        this.DataContext = allRoles;
    }
}

并在xaml

<ListView ItemsSource="{Binding}" Name="Hello">

或者,或者,您可以使AllRoles成为窗口的公共属性

public partial class MainWindow : Window
{
    public ObservableCollection<Role> AllRoles {get;private set;}
    public MainWindow()
    {
        this.InitializeComponent();
        var allRoles = new ObservableCollection<Role>()
        allRoles.Add(new Role("John", "Manager"));
        allRoles.Add(new Role("Anne", "Trainee"));
        this.AllRoles = allRoles;
    }
}

然后使用RelativeSource告诉Binding将逻辑树向上走到Window

<ListView 
  ItemsSource="{Binding AllRoles, RelativeSource={RelativeSource FindAncestor, AncestorType=Window}}" 
  Name="Hello">

这意味着"查看我的祖先,直到找到一个窗口,然后在名为AllRoles的窗口上查找公共属性".

但是,最好的方法是完全跳过frigging代码隐藏并使用MVVM模式. 我建议你是否知道你直接跳到MVVM模式.学习曲线陡峭,但你学习了关于绑定和命令以及WPF的重要,很酷的事情.