在此 Silverlight MVVM 示例中，如何将 ModelView 连接到模型？

Question

我正在使用文章 Model View View-Model (MVVM) in Silverlight 作为基础，在 Silverlight 中创建我自己的 MVVM 示例。

我已经得到了以下所有部分：

• 主页（加载所有内容）
• 查看（带有绑定的 XAML 文件）
• Model（生成虚假 List 集合的 Customer 类）
• ModelView（继承 INotifyPropertyChanged 并拥有 View 需要的两个字段的 PropertyChanged）

在我的主页上：

• 创建 ViewModel
• 将 ViewModel 绑定到 View 的 DataContext
• 创建模型（客户）

但是现在如何将 ModelView 连接到 Model？ 我觉得我需要以某种方式将客户模型注入到 CustomerViewModel 中，对吗？但具体如何？完成这个 MVVM 示例的下一步是什么，以便我可以开始使用 MVVM 模式的优点，例如用测试模型换出模型，用新视图换出视图等。

---

MainPage.xaml.cs： 创建 ViewModel，将 View 附加到 ViewModel

using System.Windows.Controls;
using System.Collections.Generic;

namespace TestMvvm345
{
    public partial class MainPage : UserControl
    {
        private CustomerViewModel customerData;

        public MainPage()
        {
            InitializeComponent();

            customerData = new CustomerViewModel();
            customerHeaderView.DataContext = customerData;
            List<Customer> customers = Customer.GetCustomers();
        }
    }
}

MainPage.xaml： 在主页的上下文中显示视图

<UserControl x:Class="TestMvvm345.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
    xmlns:local="clr-namespace:TestMvvm345"
    Width="400" Height="300">
    <Grid x:Name="LayoutRoot" Background="White">
        <StackPanel HorizontalAlignment="Left">
            <local:CustomerHeaderView x:Name="customerHeaderView" Margin="10"/>
        </StackPanel>
    </Grid>
</UserControl>

CustomerViewModel.xaml： ViewModel

using System.ComponentModel;

namespace TestMvvm345
{
    public class CustomerViewModel : INotifyPropertyChanged
    {
        private string firstName;
        private string lastName;

        public string FirstName
        {
            get { return firstName; }
            set
            {
                firstName = value;
                RaisePropertyChanged("FirstName");
            }
        }

        public string LastName
        {
            get { return lastName; }
            set
            {
                lastName = value;
                RaisePropertyChanged("LastName");
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;

        private void RaisePropertyChanged(string property)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(property));
            }
        }
    }
}

CustomerHeaderView.xaml 视图

<UserControl x:Class="TestMvvm345.CustomerHeaderView"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
    Width="400" Height="300">
    <Grid x:Name="LayoutRoot" Background="White">
        <StackPanel HorizontalAlignment="Left">
            <ListBox x:Name="CustomerList" ItemsSource="{Binding}">
                <ListBox.ItemTemplate>
                    <DataTemplate>
                        <StackPanel Orientation="Horizontal">
                            <TextBlock
                            Text="{FirstName}"/>
                            <TextBlock
                            Text="{LastName}"/>
                        </StackPanel>
                    </DataTemplate>
                </ListBox.ItemTemplate>
            </ListBox>
        </StackPanel>
    </Grid>
</UserControl>

Customers.cs 模型

using System;
using System.Collections.Generic;

namespace TestMvvm345
{
    public class Customer
    {
        public int ID { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public int NumberOfContracts { get; set; }

        public static List<Customer> GetCustomers()
        {
            List<Customer> customers = new List<Customer>();
            customers = new List<Customer>();
            customers.Add(new Customer { FirstName = "Jim", LastName = "Smith", NumberOfContracts = 23 });
            customers.Add(new Customer { FirstName = "Jane", LastName = "Smith", NumberOfContracts = 22 });
            customers.Add(new Customer { FirstName = "John", LastName = "Tester", NumberOfContracts = 33 });
            customers.Add(new Customer { FirstName = "Robert", LastName = "Smith", NumberOfContracts = 2 });
            customers.Add(new Customer { FirstName = "Hank", LastName = "Jobs", NumberOfContracts = 5 });
            return customers;
        }
    }
}

Answer 1

我使用 ViewModel 的方式有些不同。在我的例子中，它实际上包装了 Model 类，将大部分数据传递给模型。这样，模型中的所有标准业务规则仍然按照它们应该立即的方式工作。 ViewModel 仅公开数据绑定或其他 UI 目的实际需要的那些属性。此外，ViewModel 可能包含用于数据绑定的其他属性/方法。

因此，以您的客户为例： 命名空间 TestMvvm345 { 公共类 CustomerViewModel : INotifyPropertyChanged {

    private Customer _model;
    public Customer Model
    {
        get
        { return _model; }
        set
        {
            if (_model != null)
                Model.PropertyChanged -= Model_PropertyChanged;

            _model = value;

            if (_model != null)
                Model.PropertyChanged += Model_PropertyChanged;
        }
    }

    void Model_PropertyChanged(object sender, PropertyChangedEventArgs e)
    {
        RaisePropertyChanged(e.PropertyName);
        if (e.PropertyName == "FirstName" || e.PropertyName == "LastName")
            RaisePropertyChanged("FullName");
    }

    public string FirstName
    {
        get { return Model.FirstName; }
        set { Model.FirstName = value; }
    }

    public string LastName
    {
        get { return Model.LastName; }
        set { Model.LastName = value; }
    }

    public string FullName
    {
        get { return FirstName + " " + LastName; }
    }


    public static IList<CustomerViewModel> GetCustomers()
    {
        var result = new List<CustomerViewModel>();
        var customers = Customer.GetCustomers();
        foreach (var customer in customers)
        {
            result.Add(new CustomerViewModel() { Model = customer });
        }
        return result;
    }
    public event PropertyChangedEventHandler PropertyChanged;

    private void RaisePropertyChanged(string property)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(property));
        }
    }
}


public class Customer : INotifyPropertyChanged
{
    public int ID { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public int NumberOfContracts { get; set; }

    public static List<Customer> GetCustomers()
    {
        List<Customer> customers = new List<Customer>();
        customers = new List<Customer>();
        customers.Add(new Customer { FirstName = "Jim", LastName = "Smith", NumberOfContracts = 23 });
        customers.Add(new Customer { FirstName = "Jane", LastName = "Smith", NumberOfContracts = 22 });
        customers.Add(new Customer { FirstName = "John", LastName = "Tester", NumberOfContracts = 33 });
        customers.Add(new Customer { FirstName = "Robert", LastName = "Smith", NumberOfContracts = 2 });
        customers.Add(new Customer { FirstName = "Hank", LastName = "Jobs", NumberOfContracts = 5 });
        return customers;
    }

    #region INotifyPropertyChanged Members

    public event PropertyChangedEventHandler PropertyChanged;

    #endregion
}

}

现在在您的 UI 中，您可以使用以下代码进行绑定： customerHeaderView.DataContext = CustomerViewModel.GetCustomers();

ViewModel 中的代码确实变得有些大，但很多都可以放在基类中，而且模型中的所有属性都完全相同（想想 T4 模板）。