为什么在xaml中绑定ItemsSource时ui更新，而在代码中分配时却不更新？ [英] Why ui update when binding ItemsSource in xaml but doesn't when assigning it in code?

问题描述

我试图将具有 DataTemplate 的 combobox 绑定到静态方法生成的类列表 Populate（）。

I am trying to bind a combobox having a DataTemplate to a list of classes generated by a static methode Populate().

分配 combo1.ItemsSource = Peoplelist; 代码隐藏，ui中的 combobox 项目正在更新，但是当我在xaml中进行绑定时： ItemsSource = {Binding Path = Peoplelist} 不是。我缺少什么？

When assigning combo1.ItemsSource = Peoplelist; code-behinde, combobox items in ui are updating, but when I do a binding in xaml: ItemsSource="{Binding Path=Peoplelist}" it is not. What I am missing?

MainWindow.xaml.cs

using System;
using System.Collections.Generic;
using System.Windows;

namespace WpfTest
{
    public partial class MainWindow : Window
    {
        public List<People> Peoplelist;

        public MainWindow()
        {
            Peoplelist = new List<People>();
            People.Populate(Peoplelist);

            InitializeComponent();
            //combo1.ItemsSource = Peoplelist;  //working
        }
    }


    public class People
    {
        public string FirstName { get; set; }
        public string LastName { get; set; }

        public People() { }

        public People(String _FirstName, String _FamilyName)
        {
            FirstName = _FirstName;
            LastName = _FamilyName;
        }

        public static void Populate(List<People> lst)
        {
            lst.Add(new People
            {
                FirstName = "Jon",
                LastName = "Jonathan",
            });
            lst.Add(new People
            {
                FirstName = "Mark",
                LastName = "Markthan",
            });
            lst.Add(new People
            {
                FirstName = "Spence",
                LastName = "Spencer",
            });
        }
    }
}

MainWindow.xaml

<Window x:Class="WpfTest.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
           mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        <ComboBox Name="combo1" VerticalAlignment="Center" HorizontalAlignment="Center" MinWidth="200" 
          SelectedValuePath="LastName" ItemsSource="{Binding Path=Peoplelist}">
            <ComboBox.ItemTemplate>
                <DataTemplate>
                    <StackPanel Orientation="Horizontal">
                        <TextBlock Text="{Binding FirstName}"/>
                        <TextBlock Text="--"/>
                        <TextBlock Text="{Binding LastName}"/>
                    </StackPanel>
                </DataTemplate>
            </ComboBox.ItemTemplate>
        </ComboBox>
    </Grid>
</Window>

推荐答案

您的代码有两点错误。
首先：您没有在xaml或后面的代码中指定数据上下文，因此它不知道要将数据绑定到何处。
第二：您的Peoplelist应该是一个属性，因为WPF数据绑定仅适用于公共属性。

There are two things wrong with your code. First: You didn't specify a data context in your xaml or code behind so it doesn't know where the data is that you want to bind to. Second: Your Peoplelist should be a property because WPF data binding only works with public properties.

因此您的MainWindow类应该是

So your MainWindow class should be

public partial class MainWindow : Window
{
    public List<People> Peoplelist { get; set; }

    public MainWindow()
    {
        Peoplelist = new List<People>();
        People.Populate(Peoplelist);
        DataContext = this;
        InitializeComponent();
    }
}

这篇关于为什么在xaml中绑定ItemsSource时ui更新，而在代码中分配时却不更新？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！