WPF MVVM 和 RoutedEvent 入門

搜了好長時間，找到這一份容易理解的帖子。複製粘貼運行起來效果也達到了，結果發現MainWindow.cs裏沒法取得RadioButton的狀態。又Google搜了一會兒（( ఠൠఠ )ﾉ面向搜索引擎編程的我），看到別人的MainWindow()構造函數裏，有一句var viewModel = new ViewModel();DataContext = viewModel;

才明白過來，爲啥自己要照抄源碼，不動腦子。源碼XML裏設定了DataContext，我刪掉後在MainWindow()構造函數里加，不就能得到RadioButton的狀態了。如下：

<Window x:Class="WpfApp2demo.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"
        xmlns:local="clr-namespace:WpfApp2demo"
        xmlns:local_viewmodel="clr-namespace:ViewModel"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800" Closing="Window_Closing">
    <!--
    //好傻，不應該在這裏指定DataContext的，搞得MainWindow.cs裏面不能得到控件的值/
        <Window.DataContext>
        <local_viewmodel:ViewModelClass/>
    </Window.DataContext>
    -->

    <Window.Resources>
        <local_viewmodel:MyConverter x:Key="MyConverter"/>
    </Window.Resources>
    <Grid>
        <StackPanel Width="156" Orientation="Horizontal" Margin="318,131,318,0">
            <RadioButton GroupName="name" IsChecked="{Binding Path=CurrentOption, Mode=TwoWay, Converter={StaticResource MyConverter}, ConverterParameter=0}" Content="Option A" Width="45"/>
            <RadioButton GroupName="name" IsChecked="{Binding Path=CurrentOption, Mode=TwoWay, Converter={StaticResource MyConverter}, ConverterParameter=1}" Content="Option B" Width="45"/>
            <RadioButton GroupName="name" IsChecked="{Binding Path=CurrentOption, Mode=TwoWay, Converter={StaticResource MyConverter}, ConverterParameter=2}" Content="Option C" Width="60"/>

        </StackPanel>
        <Button Content="Show your selection" Command="{Binding Path=CmdShowMessage}" HorizontalAlignment="Left" Margin="342,62,0,0" VerticalAlignment="Top" Width="128"/>

    </Grid>
</Window>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

using ViewModel;

namespace WpfApp2demo
{
    /// <summary>
    /// MainWindow.xaml 的交互邏輯
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();

            InitUi();
        }

        ViewModelClass vmc1 = new ViewModelClass();

        private void InitUi()
        {
            //綁定事件/
            vmc1.ExchangeEvent += ExchangeRadioBtn;
            DataContext = vmc1;
        }

        private void ExchangeRadioBtn(object sender, RoutedEventArgs e)
        {
            MessageBox.Show("MainWindow ->RadioBtn:" + vmc1.CurrentOption);
        }

        private void Window_Closing(object sender, System.ComponentModel.CancelEventArgs e)
        {
            //ViewModelClass : Window, INotifyPropertyChanged/
            //因爲ViewModelClass繼承了Window（爲了傳路由事件）所以在關閉窗口的時候需要手動關閉，否則關閉窗口會很慢/
            vmc1.Close();
        }
    }
}

其他源碼都的內容完全是搜索引擎複製來的，我在裏面加了個路由事件

 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Data;

namespace ViewModel
{
    public class MyConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            //value是radio接到binding變數的值後，來呼叫converter
            //converter負責判定接到的值是代表true還是false
            if (value == null || parameter == null)
                return false;
            string checkvalue = value.ToString();
            string targetvalue = parameter.ToString();
            bool r = checkvalue.Equals(targetvalue,
                StringComparison.InvariantCultureIgnoreCase);
            return r;
        }

        public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            //value 是目前 radiobutton 的 true/false
            //在這裡把 parameter 傳回 View-Model
            if (value == null || parameter == null)
                return null;
            bool usevalue = (bool)value;

            if (usevalue)
                return parameter.ToString();

            return null;
        }
    }
}

 

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Input;


namespace ViewModel
{
    public class ViewModelClass : Window, INotifyPropertyChanged
    {
        #region 事件初始化
        public ViewModelClass()
        {
            cmdShowMessage = new ShowMsgCmdClass(this);

            RadioBtn_VMEvent = EventManager.RegisterRoutedEvent("RadioBtn_VMEvent",
                RoutingStrategy.Bubble, typeof(RoutedEventHandler), typeof(ViewModelClass));
        }

        public static RoutedEvent RadioBtn_VMEvent;
        public event RoutedEventHandler ExchangeEvent
        {
            add { base.AddHandler(RadioBtn_VMEvent, value); }
            remove { base.RemoveHandler(RadioBtn_VMEvent, value); }
        }
        #endregion

        string currentOption;

        public string CurrentOption
        {
            get
            {
                return currentOption;
            }
            set
            {
                if (value != null) //要判斷一下是否為 null，否則選了A，又選B時，最後一個回傳的會是A的值，這樣就抓不到了。
                    currentOption = value;
            }
        }

        ShowMsgCmdClass cmdShowMessage;

        public ShowMsgCmdClass CmdShowMessage
        {
            get { return cmdShowMessage; }
            set { cmdShowMessage = value; }
        }

        public event PropertyChangedEventHandler PropertyChanged;
        public void OnPropertyChanged(string prop)
        {
            PropertyChangedEventHandler handler = PropertyChanged;
            if (handler != null)
                handler(this, new PropertyChangedEventArgs(prop));
        }

        public void ShowMsg()
        {
            System.Windows.MessageBox.Show("You Select " + currentOption);

            RoutedEventArgs args = new RoutedEventArgs(RadioBtn_VMEvent, this);
            //調用元素的RaiseEvent方法（繼承自UIElement類），將事件發出去
            this.RaiseEvent(args);
        }
    }
}

 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Input;

namespace ViewModel
{
    public class ShowMsgCmdClass : ICommand
    {
        ViewModelClass vm;
        public ShowMsgCmdClass(ViewModelClass fvm)
        {
            vm = fvm;
        }
        public bool CanExecute(object parameter)
        {
            return true;
        }

        public event EventHandler CanExecuteChanged;

        public void Execute(object parameter)
        {
            vm.ShowMsg();
        }
    }
}