WPF - MVVM：以后的SelectionChanged组合框值 [英] WPF - MVVM: ComboBox value after SelectionChanged
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问题描述
我是新的C＃和MVVM，我已经花了一整天试图让的SelectionChanged一个。我设法用弄明白要么组合框我的视图模型的价值 CallMethodAction 或 InvokeCommandAction 与资源：
-
System.Windows.Interactivity.dll -
Microsoft.Ex pression.Interactions.dll
我的问题是，这两种方法返回之前，它已经改变了组合框的值。任何人都可以解释如何获取值的之后的变化？
我花了几个小时寻遍SO和谷歌的解决方案，所以我不知道如果其他人也有同感。任何意见将是AP preciated！
我的code是如下：
MainWindow.xaml
＆LT;窗口x：类=SelectionChange.MainWindow
的xmlns =http://schemas.microsoft.com/winfx/2006/xaml/$p$psentation
的xmlns：X =http://schemas.microsoft.com/winfx/2006/xaml
的xmlns：I =CLR的命名空间：System.Windows.Interactivity;装配= System.Windows.Interactivity
xmlns:si=\"clr-namespace:Microsoft.Ex$p$pssion.Interactivity.Core;assembly=Microsoft.Ex$p$pssion.Interactions\"
的xmlns：VM =CLR的命名空间：SelectionChange
标题=主窗口WIDTH =300HEIGHT =300＆GT;
＆LT; Window.DataContext＆GT;
＆LT; VM：视图模型/＆GT;
＆LT; /Window.DataContext>
＆LT;网格和GT;
＆LT;组合框名称=选择框VerticalAlignment =顶部的SelectedIndex =0＆GT;
＆LT; I：Interaction.Triggers＆GT;
＆LT; I：的EventTrigger事件名称=的SelectionChanged＆GT;
＆LT; SI：CallMethodAction方法名=的SelectionChangedTargetObject ={结合}/＆GT;
！＆LT; - ＆LT; I：InvokeCommandAction命令={结合SelectionChangedCommand}CommandParameter ={绑定的ElementName =选择框，路径=文本}/＆GT; - ＆GT;
＆LT; /我：＆的EventTrigger GT;
＆LT; /我：Interaction.Triggers＆GT;
＆LT; ComboBoxItem CONTENT =项目1/＆GT;
＆LT; ComboBoxItem CONTENT =项目2/＆GT;
＆LT; ComboBoxItem CONTENT =项目3/＆GT;
＆LT; /组合框＆GT;
＆LT; /网格和GT;
＆LT; /窗GT;
ViewModel.cs
命名空间SelectionChange
{
使用系统;
使用System.Windows;
使用System.Windows.Controls的;
使用System.Windows.Input; 公共类视图模型
{
公共视图模型（）
{
SelectionChangedCommand =新SelectionChangedCommand（）;
} 公众的ICommand SelectionChangedCommand
{
得到;
组;
} 公共无效的SelectionChanged（对象发件人，EventArgs的发送）
{
组合框选择框=（组合框）发送;
的MessageBox.show（叫的SelectionChanged：+ SelectBox.Text）;
}
}
}
SelectionChangedCommand.cs
命名空间SelectionChange
{
使用系统;
使用System.Windows;
使用System.Windows.Controls的;
使用System.Windows.Input; 公共类SelectionChangedCommand：ICommand的
{
公共SelectionChangedCommand（）
{
} 公共事件的EventHandler CanExecuteChanged; 公共BOOL CanExecute（对象参数）
{
返回true;
} 公共无效执行（对象参数）
{
的MessageBox.show（执行的SelectionChangedCommand：+参数）;
}
}
}
结果搜索结果
修改：我的解决方案
原来我不明白绑定不够好，而是试图实现东西在一个相当复杂的方式简单！而不是使用依赖，现在我已经实现了我所需要使用普通绑定。举个例子，我约束的文本框到的SelectedIndex 的组合框，这将会采用更新的 INotifyPropertyChanged的。
MainWindow.xaml
＆LT;窗口x：类=SelectionChange.MainWindow
的xmlns =http://schemas.microsoft.com/winfx/2006/xaml/$p$psentation
的xmlns：X =http://schemas.microsoft.com/winfx/2006/xaml
的xmlns：VM =CLR的命名空间：SelectionChange
标题=主窗口WIDTH =300HEIGHT =300＆GT;
＆LT; Window.DataContext＆GT;
＆LT; VM：视图模型/＆GT;
＆LT; /Window.DataContext>
＆LT;网格和GT;
＆LT; Grid.ColumnDefinitions＆GT;
＆LT; ColumnDefinition WIDTH =自动/＆GT;
＆所述; ColumnDefinition宽度=*/＆GT;
＆LT; /Grid.ColumnDefinitions> ＆LT;组合框的SelectedItem ={结合的SelectedItem}的SelectedIndex =0Grid.Column =0VerticalAlignment =评出的＆GT;
＆LT; ComboBoxItem CONTENT =项目1/＆GT;
＆LT; ComboBoxItem CONTENT =项目2/＆GT;
＆LT; ComboBoxItem CONTENT =项目3/＆GT;
＆LT; /组合框＆GT; ＆LT;！ - 文本框来显示组合框的selectedIndex - ＆GT;
＆LT;文本框的文本={结合的SelectedIndex}Grid.Column =1VerticalAlignment =顶部/＆GT;
＆LT; /网格和GT;
＆LT; /窗GT;
ViewModel.cs
命名空间SelectionChange
{
使用系统;
使用System.ComponentModel;
使用System.Windows.Controls的; 公共类视图模型：INotifyPropertyChanged的
{
公共视图模型（）
{
} //属性来存储/检索组合框的selectedIndex
私人诠释_SelectedIndex;
公众诠释的SelectedIndex {搞定;组; } //属性绑定到组合框的的SelectedItem
私人ComboBoxItem _SelectedItem;
公共ComboBoxItem的SelectedItem
{
{返回_SelectedItem; }
组
{
_SelectedItem =价值; //的SelectedItem的内容
字符串内容=（字符串）value.Content; //的SelectedItem的母公司（即组合框）
组合框选择框=（组合框）value.Parent; //组合框的selectedIndex
INT指数= SelectBox.SelectedIndex; //存放的SelectedIndex在属性
的SelectedIndex =指数; //提高的PropertyChanged与存储的属性的名称
RaisePropertyChanged（的SelectedIndex）;
}
} // INotifyPropertyChanged的
公共事件PropertyChangedEventHandler的PropertyChanged;
私人无效RaisePropertyChanged（字符串属性名）
{
如果（的PropertyChanged！= NULL）
的PropertyChanged（这一点，新PropertyChangedEventArgs（属性名））;
}
}
}
解决方案
为什么不这样做的简单的方法
＆LT;组合框了maxHeight =25
的ItemsSource ={绑定源}
的SelectedItem ={结合TheSelectedItem，模式=双向}/＆GT;
在您的视图模型声明组合框项目和使用财产来源，使其返回到视图
列表＆LT;串GT; _source =新的List＆LT;串GT; {项目1，项目2，3项};
公开名单＆LT;串GT;资源
{
{返回_source; }
}
然后定义它保存所选的项目一个属性。
字符串_theSelectedItem = NULL;
公共字符串TheSelectedItem
{
{返回_theSelectedItem; }
集合{_theSelectedItem =价值; } // NotifyPropertyChanged
}
另外，不要忘记实现INotifyPropertyChanged接口，同时设置_source
I am new to C# and MVVM, and I've spent all day trying to get the value of a ComboBox to my ViewModel on SelectionChanged. I have managed to figure it out using either CallMethodAction or InvokeCommandAction with the resources:
System.Windows.Interactivity.dllMicrosoft.Expression.Interactions.dll
My problem is that both these methods return the value of the ComboBox before it has changed. Could anyone explain how to get the value after the change?
I have spent hours searching through SO and Google for a solution, so I wonder if others are too. Any advice will be appreciated!
My code is below:
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);
}
}
}
Edit: My Solution
It turns out I didn't understand Binding well enough and instead was trying to implement something simple in a rather complicated way! Instead of using dependencies, I have now achieved what I needed using regular bindings. As an example, I've bound a TextBox to the SelectedIndex of the ComboBox, which gets updated using INotifyPropertyChanged.
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));
}
}
}
解决方案
Why not do it the simpler way
<ComboBox MaxHeight="25"
ItemsSource="{Binding Source}"
SelectedItem="{Binding TheSelectedItem, Mode=TwoWay}" />
In your ViewModel declare the combo box items and use a property "Source" to return it to the view
List<string> _source = new List<string>{"Item 1", "Item 2", "Item 3"};
public List<string> Source
{
get { return _source; }
}
Then define one property which holds the selected item
string _theSelectedItem = null;
public string TheSelectedItem
{
get { return _theSelectedItem; }
set { _theSelectedItem = value; } // NotifyPropertyChanged
}
Also don't forget to implement the INotifyPropertyChanged interface while setting the _source
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