c# – WPF – MVVM：SelectionChanged后的ComboBox值

概述我是C#和MVVM的新手,我花了一整天的时间尝试将ComboBox的值添加到SelectionChanged上的ViewModel.我已经设法使用CallMethodAction或InvokeCommandAction与资源： > System.Windows.Interactivity.dll > Microsoft.Expression.Interactions.dll 我的问题是这两个方法在 我是C#和MVVM的新手,我花了一整天的时间尝试将ComboBox的值添加到SelectionChanged上的viewmodel.我已经设法使用CallMethodAction或InvokeCommandAction与资源：

> System.Windows.Interactivity.dll
> Microsoft.Expression.Interactions.dll

我的问题是这两个方法在更改之前返回ComboBox的值.任何人都可以解释如何在变更后获得价值？

我花了几个小时通过SO和Google搜索解决方案,所以我想知道其他人是否也是.任何建议将不胜感激！

我的代码如下：

MainWindow.xaml

<Window x:Class="SelectionChange.MainWindow"        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"        xmlns:i="clr-namespace:System.windows.Interactivity;assembly=System.windows.Interactivity"        xmlns:si="clr-namespace:Microsoft.Expression.Interactivity.Core;assembly=Microsoft.Expression.Interactions"        xmlns:vm="clr-namespace:SelectionChange"        title="MainWindow" WIDth="300" Height="300">    <Window.DataContext>        <vm:viewmodel />    </Window.DataContext>    <GrID>        <ComboBox name="SelectBox" VerticalAlignment="top" Selectedindex="0">            <i:Interaction.Triggers>                <i:EventTrigger Eventname="SelectionChanged">                    <si:CallMethodAction Methodname="SelectionChanged" Targetobject="{Binding}" />                    <!--<i:InvokeCommandAction Command="{Binding SelectionChangedCommand}" CommandParameter="{Binding Elementname=SelectBox,Path=Text}" />-->                </i:EventTrigger>            </i:Interaction.Triggers>            <ComboBoxItem Content="Item 1" />            <ComboBoxItem Content="Item 2" />            <ComboBoxItem Content="Item 3" />        </ComboBox>    </GrID></Window>

viewmodel.cs

namespace SelectionChange{    using System;    using System.windows;    using System.windows.Controls;    using System.windows.input;    public class viewmodel    {        public viewmodel()        {            SelectionChangedCommand = new SelectionChangedCommand();        }        public ICommand SelectionChangedCommand        {            get;            set;        }        public voID SelectionChanged(object sender,EventArgs e)        {            ComboBox SelectBox = (ComboBox)sender;            MessageBox.Show("Called SelectionChanged: " + SelectBox.Text);        }    }}

SelectionChangedCommand.cs

namespace SelectionChange{    using System;    using System.windows;    using System.windows.Controls;    using System.windows.input;    public class SelectionChangedCommand : ICommand    {        public SelectionChangedCommand()        {        }        public event EventHandler CanExecuteChanged;        public bool CanExecute(object parameter)        {            return true;        }        public voID Execute(object parameter)        {            MessageBox.Show("Executed SelectionChangedCommand: " + parameter);        }    }}

编辑：我的解决方案

事实证明,我不明白Binding足够好,而是试图以一个相当复杂的方式实现一些简单的东西！而不是使用依赖关系,我现在已经使用常规绑定实现了我所需要的.例如,我已经将一个TextBox绑定到ComboBox的Selectedindex,它使用INotifyPropertyChanged进行更新.

MainWindow.xaml

<Window x:Class="SelectionChange.MainWindow"        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"        xmlns:vm="clr-namespace:SelectionChange"        title="MainWindow" WIDth="300" Height="300">    <Window.DataContext>        <vm:viewmodel />    </Window.DataContext>    <GrID>        <GrID.ColumnDeFinitions>            <ColumnDeFinition WIDth="auto" />            <ColumnDeFinition WIDth="*" />        </GrID.ColumnDeFinitions>        <ComboBox SelectedItem="{Binding SelectedItem}" Selectedindex="0" GrID.Column="0" VerticalAlignment="top">            <ComboBoxItem Content="Item 1" />            <ComboBoxItem Content="Item 2" />            <ComboBoxItem Content="Item 3" />        </ComboBox>        <!-- TextBox to display the ComboBox's Selectedindex -->        <TextBox Text="{Binding Selectedindex}" GrID.Column="1" VerticalAlignment="top" />    </GrID></Window>

viewmodel.cs

namespace SelectionChange{    using System;    using System.ComponentModel;    using System.windows.Controls;    public class viewmodel : INotifyPropertyChanged    {        public viewmodel()        {           }        // Property to store / retrIEve ComboBox's Selectedindex        private int _Selectedindex;        public int Selectedindex { get; set; }        // Property to bind to ComboBox's SelectedItem        private ComboBoxItem _SelectedItem;        public ComboBoxItem SelectedItem        {            get { return _SelectedItem; }            set            {                _SelectedItem = value;                // SelectedItem's Content                string Content = (string)value.Content;                // SelectedItem's parent (i.e. the ComboBox)                ComboBox SelectBox = (ComboBox)value.Parent;                // ComboBox's Selectedindex                int Index = SelectBox.Selectedindex;                // Store the Selectedindex in the property                Selectedindex = Index;                // Raise PropertyChanged with the name of the stored property                RaisePropertyChanged("Selectedindex");            }        }        // INotifyPropertyChanged        public event PropertyChangedEventHandler PropertyChanged;        private voID RaisePropertyChanged(string Propertyname)        {            if (PropertyChanged != null)                PropertyChanged(this,new PropertyChangedEventArgs(Propertyname));        }    }}

解决方法 为什么不这样做简单一些

<ComboBox MaxHeight="25"           ItemsSource="{Binding Source}"           SelectedItem="{Binding TheSelectedItem,Mode=TwoWay}" />

在您的viewmodel中声明组合框项目并使用属性“Source”将其返回到视图

List<string> _source = new List<string>{"Item 1","Item 2","Item 3"};public List<string> Source {     get { return _source; } }

然后定义一个保存所选项目的属性

string _theSelectedItem = null;public string TheSelectedItem {     get { return _theSelectedItem; }     set { _theSelectedItem = value; } // NotifyPropertyChanged}

在设置_source时也不要忘记实现INotifyPropertyChanged接口

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