【发布时间】：2020-07-22 17:37:03
【问题描述】：
我的问题分为两部分：
- 在 xaml 中使用
Content="{Binding SelectedPerson.Age}"而不是SelectedPersonAge.Content = SelectedPerson.Age;指的是Why binding using ItemsSource is working in code but not in xaml?。我已经设置了datacontext和SelectedPerson是一个属性。 - 即使在组合框项目更改时更新（使用后面的代码），当所选项目标签字段的属性之一发生修改时，我尝试实现 INotifyPropertyChanged 但它在
.add().delete()时触发.clear()参与，但与Peoplelist[0].Age = 5;无关。
我做错了什么？不使用复杂的mvvm外部框架，是否可以通过简单的代码来实现？
Mainwindow.xaml.cs
using System;
using System.Collections.ObjectModel;
using System.Windows;
using System.ComponentModel;
using System.Runtime.CompilerServices;
namespace WpfTest
{
public partial class MainWindow : Window, INotifyPropertyChanged
{
public ObservableCollection<People> Peoplelist { get; set; } = new ObservableCollection<People>();
public event PropertyChangedEventHandler PropertyChanged;
private People _SelectedPerson;
public People SelectedPerson
{
get { return _SelectedPerson; }
set
{
if (value != _SelectedPerson)
{
_SelectedPerson= value;
NotifyPropertyChanged("SelectedPerson");
}
}
}
private void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
public MainWindow()
{
People.Populate(Peoplelist);
InitializeComponent();
DataContext = this;
}
private void Button_Click(object sender, RoutedEventArgs e)
{
//Modify Jon's Age property while it's selected: not automatically updating in ui
Peoplelist[0].Age = 5;
}
private void combo1_SelectionChanged(object sender, System.Windows.Controls.SelectionChangedEventArgs e)
{
SelectedPersonAge.Content = SelectedPerson.Age; //not working when put in xaml
}
}
public class People : INotifyPropertyChanged
{
public string FirstName { get; set; }
public string LastName { get; set; }
private int _Age;
public int Age
{
get { return _Age; }
set
{
_Age = value;
RaisePropertyChanged("Age");
}
}
public event PropertyChangedEventHandler PropertyChanged;
private void RaisePropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
public People() { }
public People(String _FirstName, String _FamilyName)
{
FirstName = _FirstName;
LastName = _FamilyName;
Age = 0;
}
public static void Populate(ObservableCollection<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>
<StackPanel>
<ComboBox Name="combo1" VerticalAlignment="Center" HorizontalAlignment="Center" MinWidth="200" SelectedValuePath="Age" SelectionChanged="combo1_SelectionChanged" ItemsSource="{Binding Path=Peoplelist}" SelectedItem="{Binding SelectedPerson}">
<ComboBox.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding FirstName}"/>
<TextBlock Text="--"/>
<TextBlock Text="{Binding LastName}"/>
</StackPanel>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
<Label Name="SelectedPersonAge" Width="200" Height="35" HorizontalAlignment="center" VerticalAlignment="center" Content="{Binding SelectedPerson.Age}"/>
<Button Height="35" Click="Button_Click">
Test
</Button>
</StackPanel>
</Grid>
</Window>
【问题讨论】：
-
暂时忽略使用
this作为窗口数据上下文的非常不明智的选择，您甚至没有在Label中使用它，而是明确地将数据上下文设置为字符串"combo1"。即使您使用了{x:Reference...}，上下文仍然是错误的，因为它是具有您想要的属性的窗口，而不是ComboBox。目前尚不清楚您为什么要在此处设置DataContext属性...我建议将其删除。如果您这样做，它可能会“正常”工作（同样，不包括将视图模型内容放入窗口的更广泛的问题）。 -
@PeterDuniho 哦，这太傻了，抱歉我对这一切都不熟悉。当我在标签中设置
DataContext="{Binding}时，确实一切正常。但是，如果我从代码comobobox 中删除DataContext = this;变为空，我应该如何解决这个问题？我把所有东西都放在主窗口中只是为了测试。 -
@PeterDuniho 在组合框和标签
DataContext="{Binding ElementName=MyWindow}中设置的 DataContext 下一切正常。谢谢。
标签： c# wpf xaml binding observablecollection