【WPF学习手记】实例学习WPF的MVVM编程模式3

    程序功能：有两个ComboBox，第一个ComboBox的ComboBoxItem为Name、Age和Sex，第二个ComboBox的ComboBoxItem为一个类，类中包含了Name、Age和Sex三个字段；根据第一个ComboBox选中的内容，来确定第二个ComboBox要显示字段。

    同时，当鼠标进入第二个ComboBox时，会显示ToolTip，即完成一个控件的多个操作。

•  NotificationObject.cs

using System.ComponentModel;

namespace MVVMDemo3.ViewModel
{
    class NotificationObject : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;

        public void RaisePropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged.Invoke(this, new PropertyChangedEventArgs(propertyName));
            }
        }
    }
}

• DelegateCommand.cs

using System;
using System.Windows.Input;

namespace MVVMDemo3.Commands
{
    class DelegateCommand : ICommand
    {
        public event EventHandler CanExecuteChanged;

        public bool CanExecute(object parameter)
        {
            if (CanExecuteFunc == null)
            {
                return true;
            }
            return CanExecuteFunc(parameter);
        }

        public void Execute(object parameter)
        {
            if (ExecuteAction == null)
            {
                return;
            }
            ExecuteAction(parameter);
        }

        public Action<object> ExecuteAction { set; get; }
        public Func<object, bool> CanExecuteFunc { get; set; }
    }
}

• Student.cs

namespace MVVMDemo3.Models
{
    class Student
    {
        public string Name { get; set; }
        public int Age { get; set; }
        public string Sex { get; set; }
    }
}

• MainWindowViewModel.cs

using System;
using MVVMDemo3.Commands;
using MVVMDemo3.Models;
using System.Collections.Generic;

namespace MVVMDemo3.ViewModel
{
    class MainWindowViewModel : NotificationObject
    {
        private string currentStudent;

        public string CurrentStudent
        {
            get { return currentStudent; }
            set
            {
                currentStudent = value;
                RaisePropertyChanged("CurrentStudent");
            }
        }

        private int selectedIndex;

        public int SelectedIndex
        {
            get { return selectedIndex; }
            set
            {
                selectedIndex = value;
                RaisePropertyChanged("SelectedIndex");
            }
        }

        private List<Student> studentInformations;

        public List<Student> StudentInformations
        {
            get { return studentInformations; }
            set
            {
                studentInformations = value;
                RaisePropertyChanged("StudentInformations");
            }
        }

        private string showContent;

        public string ShowContent
        {
            get { return showContent; }
            set
            {
                showContent = value;
                RaisePropertyChanged("ShowContent");
            }
        }

        public DelegateCommand SelectedCommand { get; set; }

        public void Selected(object parameter)
        {
            CurrentStudent = StudentInformations[SelectedIndex].Name + " " + StudentInformations[SelectedIndex].Age.ToString() + " " + 
                             StudentInformations[SelectedIndex].Sex;
            if (SelectedIndex == 0)
            {
                ShowContent = "Name";
            }
            else if (SelectedIndex == 1)
            {
                ShowContent = "Age";
            }
            else
            {
                ShowContent = "Sex";
            }
        }

        public MainWindowViewModel()
        {
            StudentInformations = new List<Student>
            {
                new Student()
                {
                    Name = "Tom",
                    Age = 20,
                    Sex = "Man",
                },
                new Student()
                {
                    Name = "Jack",
                    Age = 21,
                    Sex = "Man",
                },
                new Student()
                {
                    Name = "Lucy",
                    Age = 22,
                    Sex = "Woman",
                },
            };
            SelectedIndex = 0;
            ShowContent = "Name";
            CurrentStudent = StudentInformations[0].Name + " " + StudentInformations[0].Age.ToString() + " " + StudentInformations[0].Sex;

            SelectedCommand = new DelegateCommand()
            {
                ExecuteAction = new Action<object>(Selected),
            };
        }
    }
}

• 主xaml文件

<Window x:Class="MVVMDemo3.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:MVVMDemo3.ViewModel"
        xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
        mc:Ignorable="d"
        Title="MainWindow" Height="150" Width="400">
    <Window.DataContext>
        <local:MainWindowViewModel/>
    </Window.DataContext>
    <Grid Margin="5">
        <StackPanel Margin="5">
            <TextBlock Margin="5" Width="300" Height="30" VerticalAlignment="Center" Text="{Binding CurrentStudent}"/>
            <StackPanel Orientation="Horizontal" HorizontalAlignment="Center">
                <ComboBox Height="30" VerticalContentAlignment="Center" Margin="5" SelectedIndex="{Binding SelectedIndex}">
                    <ComboBoxItem Content="Name"/>
                    <ComboBoxItem Content="Age"/>
                    <ComboBoxItem Content="Sex"/>
                </ComboBox>
                <ComboBox Width="250" Height="30" VerticalContentAlignment="Center" Margin="5" 
                          ToolTip="{Binding ShowContent}"
                          ItemsSource="{Binding StudentInformations}" 
                          DisplayMemberPath="{Binding ShowContent}"
                          SelectedIndex="{Binding SelectedIndex}">
                    <i:Interaction.Triggers>
                        <i:EventTrigger EventName="SelectionChanged">
                            <i:InvokeCommandAction Command="{Binding SelectedCommand}"/>
                        </i:EventTrigger>
                        <i:EventTrigger EventName="MouseEnter">
                            <i:InvokeCommandAction Command="{Binding TooltipCommand}"/>
                        </i:EventTrigger>
                    </i:Interaction.Triggers>
                </ComboBox>
            </StackPanel>
        </StackPanel>
    </Grid>
</Window>

• 完整代码

https://download.youkuaiyun.com/download/u012366767/10620107