Question

我在其他帖子中读过，可以在XAML中指定代替在其后面的代码中指定DataContext。

我在我的主类的构造函数中声明并填充了一个ObservableCollection，我也设置了DataContext：

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

namespace ItemsControlDemo
{
    public partial class MainWindow : Window
    {
        public ObservableCollection<Person> PersonList { get; set; }

        public MainWindow()
        {
            InitializeComponent();

            PersonList = new ObservableCollection<Person>();

            PersonList.Add(new Person(16, "Abraham", "Lincoln"));
            PersonList.Add(new Person(32, "Franklin", "Roosevelt"));
            PersonList.Add(new Person(35, "John", "Kennedy"));
            PersonList.Add(new Person(2, "John", "Adams"));
            PersonList.Add(new Person(1, "George", "Washington"));
            PersonList.Add(new Person(7, "Andrew", "Jackson"));

            DataContext = this;
        }

        private void Button_Add_Click(object sender, RoutedEventArgs e)
        {
            PersonList.Add(new Person(3, "Thomas", "Jefferson"));
        }

        private void Button_Remove_Click(object sender, RoutedEventArgs e)
        {
            PersonList.Remove(TheDataGrid.SelectedItem as Person);
        }
    }

    public class Person
    {
        public Person() { }

        public Person(int id, string firstName, string lastName)
        {
            ID = id;
            FirstName = firstName;
            LastName = lastName;
        }

        public int ID { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
    }
}

如果我这样做，一切都适用于我的应用程序。

但是，如果我删除“DataContext = this;”从构造函数中，而不是在我的应用程序的Window元素中设置DataContext

        DataContext="{Binding RelativeSource={RelativeSource Self}}"

我没有数据。

这是我从后面的代码中删除DataContext后设置DataContext的XAML：

<Window x:Class="ItemsControlDemo.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:ItemsControlDemo"
        Title="Items Control Demo" Height="350" Width="400"
        WindowStartupLocation="CenterScreen"
        DataContext="{Binding RelativeSource={RelativeSource Self}}">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="*"/>
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>
        <DataGrid Grid.Row="0" Name="TheDataGrid" SelectedValuePath="ID"
                  AutoGenerateColumns="False"
                  AlternatingRowBackground="Bisque"
                  ItemsSource="{Binding PersonList}">
            <DataGrid.Columns>
                <DataGridTextColumn Header="ID"         Binding="{Binding Path=ID}"/>
                <DataGridTextColumn Header="First Name" Binding="{Binding Path=FirstName}"/>
                <DataGridTextColumn Header="Last Name"  Binding="{Binding Path=LastName}"/>
            </DataGrid.Columns>
        </DataGrid>
        <StackPanel Grid.Row="1" Orientation="Horizontal"
                    HorizontalAlignment="Left" VerticalAlignment="Bottom">
            <Button Content="Add Item"    Margin="5" Click="Button_Add_Click"/>
            <Button Content="Remove Item" Margin="5" Click="Button_Remove_Click"/>
        </StackPanel>
    </Grid>
</Window>

对我所做错误的任何帮助都将不胜感激。

谢谢！

Answer 1

您需要在调用InitializeComponent

之前设置源
编辑：实际上你只需要在InitializeComponent之前实例化它，因为它是一个ObservableCollection它实现了INotifyCollectionChanged，所以如果你修改了这个集合，你的网格将会随着这些变化而更新。

public MainWindow() { PersonList = new ObservableCollection<Person>(); InitializeComponent(); PersonList.Add(new Person(16, "Abraham", "Lincoln")); PersonList.Add(new Person(32, "Franklin", "Roosevelt")); PersonList.Add(new Person(35, "John", "Kennedy")); PersonList.Add(new Person(2, "John", "Adams")); PersonList.Add(new Person(1, "George", "Washington")); PersonList.Add(new Person(7, "Andrew", "Jackson")); }

Answer 2

216回答是有效的。或者，您可以实施INotifyPropertyChanged，以便在设置PersonList时通知XAML。

ObservableCollection仅在集合中项目更改时通知。如果您想在为信息分配新值时通知（例如PersonList = new ObservableCollection<Person>()），则需要实施INotifyPropertyChanged。

public partial class MainWindow : Window, INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    private ObservableCollection<Person> personList;

    public ObservableCollection<Person> PersonList
    {
        get { return personList; }
        set
        {
            if (value == personList)
                return;
            personList = value;
            if (PropertyChanged != null)
                PropertyChanged(this, new PropertyChangedEventArgs("PersonList"));
        }
    }

    public MainWindow()
    {
        InitializeComponent();

        PersonList = new ObservableCollection<Person>();

        // etc.
    }
}

在XAML中设置DataContext而不是在Code Behind中

2 个答案: