MVVM: 通过 Binding 或 x:Bind 结合 Command 实现，通过 ButtonBase 触发命令
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介绍
背水一战 Windows 10 之 MVVM（Model-View-ViewModel）
- 通过 Binding 或 x:Bind 结合 Command 实现，通过 ButtonBase 触发命令
示例
1、Model
MVVM/Model/Product.cs
/*
* Model 层的实体类，如果需要通知则需要实现 INotifyPropertyChanged 接口
*/
using System.ComponentModel;
namespace Windows10.MVVM.Model
{
public class Product : INotifyPropertyChanged
{
public Product()
{
ProductId = 0;
Name = "";
Category = "";
}
private int _productId;
public int ProductId
{
get { return _productId; }
set
{
_productId = value;
RaisePropertyChanged(nameof(ProductId));
}
}
private string _name;
public string Name
{
get { return _name; }
set
{
_name = value;
RaisePropertyChanged(nameof(Name));
}
}
private string _category;
public string Category
{
get { return _category; }
set
{
_category = value;
RaisePropertyChanged(nameof(Category));
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected void RaisePropertyChanged(string name)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(name));
}
}
}
}
MVVM/Model/ProductDatabase.cs
/*
* Model 层的数据持久化操作（本地或远程）
*
* 本例只是一个演示
*/
using System;
using System.Collections.Generic;
using System.Linq;
namespace Windows10.MVVM.Model
{
public class ProductDatabase
{
private List<Product> _products = null;
public List<Product> GetProducts()
{
if (_products == null)
{
Random random = new Random();
_products = new List<Product>();
for (int i = 0; i < 100; i++)
{
_products.Add
(
new Product
{
ProductId = i,
Name = "Name" + i.ToString().PadLeft(4, \'0\'),
Category = "Category" + (char)random.Next(65, 91)
}
);
}
}
return _products;
}
public List<Product> GetProducts(string name, string category)
{
return GetProducts().Where(p => p.Name.Contains(name) && p.Category.Contains(category)).ToList();
}
public void Update(Product product)
{
var oldProduct = _products.Single(p => p.ProductId == product.ProductId);
oldProduct = product;
}
public Product Add(string name, string category)
{
Product product = new Product();
product.ProductId = _products.Max(p => p.ProductId) + 1;
product.Name = name;
product.Category = category;
_products.Insert(0, product);
return product;
}
public void Delete(Product product)
{
_products.Remove(product);
}
}
}
2、ViewModel
MVVM/ViewModel1/MyCommand.cs
/*
* 为了方便使用，把 ICommand 再封装一层
*/
using System;
using System.Windows.Input;
namespace Windows10.MVVM.ViewModel1
{
public class MyCommand : ICommand
{
// 由 public void Execute(object parameter) 调用的委托
public Action<object> MyExecute { get; set; }
// 由 public bool CanExecute(object parameter) 调用的委托
public Func<object, bool> MyCanExecute { get; set; }
public MyCommand(Action<object> execute, Func<object, bool> canExecute)
{
this.MyExecute = execute;
this.MyCanExecute = canExecute;
}
// 需要发布此事件的话，则调用 RaiseCanExecuteChanged 方法即可
public event EventHandler CanExecuteChanged;
public void RaiseCanExecuteChanged()
{
if (CanExecuteChanged != null)
{
CanExecuteChanged(this, EventArgs.Empty);
}
}
// 用于决定当前绑定的 Command 能否被执行
// parameter 是由 ButtonBase 的 CommandParameter 传递过来的
// 如果返回 false 则对应的 ButtonBase 将变为不可用
public bool CanExecute(object parameter)
{
return this.MyCanExecute == null ? true : this.MyCanExecute(parameter);
}
// 用于执行对应的命令，只有在 CanExecute() 返回 true 时才可以被执行
// parameter 是由 ButtonBase 的 CommandParameter 传递过来的对象
public void Execute(object parameter)
{
this.MyExecute(parameter);
}
}
}
MVVM/ViewModel1/ProductViewModel.cs
/* * ViewModel 层 * * 注：为了方便使用，此例对 ICommand 做了一层封装。如果需要了解比较原始的 MVVM 实现请参见 http://www.cnblogs.com/webabcd/archive/2013/08/29/3288304.html */ using System; using System.Collections.ObjectModel; using System.ComponentModel; using Windows10.MVVM.Model; namespace Windows10.MVVM.ViewModel1 { public class ProductViewModel : INotifyPropertyChanged { // 用于提供 Products 数据 private ObservableCollection<Product> _products; public ObservableCollection<Product> Products { get { return _products; } set { _products = value; RaisePropertyChanged(nameof(Products)); } } // 用于“添加”和“查询”的 Product 对象 private Product _product; public Product Product { get { return _product; } set { _product = value; RaisePropertyChanged(nameof(Product)); } } // 数据库对象 private ProductDatabase _context = null; public ProductViewModel() { _context = new ProductDatabase(); Product = new Product(); Products = new ObservableCollection<Product>(_context.GetProducts()); } private MyCommand _getProductsCommand; public MyCommand GetProductsCommand { get { return _getProductsCommand ?? (_getProductsCommand = new MyCommand ((object obj) => { // 从 Model 层获取数据 Products = new ObservableCollection<Product>(_context.GetProducts(Product.Name, Product.Category)); }, null)); } } private MyCommand _addProductCommand; public MyCommand AddProductCommand { get { return _addProductCommand ?? (_addProductCommand = new MyCommand ((object obj) => { // 在 Model 层添加一条数据 Product newProduct = _context.Add(Product.Name, Product.Category); // 更新 ViewModel 层数据 Products.Insert(0, newProduct); }, null)); } } private MyCommand _updateProductCommand; public MyCommand UpdateProductCommand { get { return _updateProductCommand ?? (_updateProductCommand = new MyCommand ((object obj) => { // 通过 CommandParameter 传递过来的数据 Product product = obj as Product; // 更新 ViewModel 层数据 product.Name = product.Name + "U"; product.Category = product.Category + "U"; // 更新 Model 层数据 _context.Update(product); }, // 对应 ICommand 的 CanExecute()，如果返回 false 则对应的 ButtonBase 将变为不可用 (object obj) => obj != null)); } } private MyCommand _deleteProductCommand; public MyCommand DeleteProductCommand { get { return _deleteProductCommand ?? (_deleteProductCommand = new MyCommand ((object obj) => { // 通过 CommandParameter 传递过来的数据 Product product = obj as Product; // 更新 Model 层数据 _context.Delete(product); // 更新 ViewModel 层数据 Products.Remove(product); }, // 对应 ICommand 的 CanExecute()，如果返回 false 则对应的 ButtonBase 将变为不可用 (object obj) => obj != null)); } } public event PropertyChangedEventHandler PropertyChanged; protected void RaisePropertyChanged(string name) { if (PropertyChanged != null) { PropertyChanged(this, new PropertyChangedEventArgs(name)); } } } }
3、View
MVVM/View/Demo1.xaml
<Page
x:Class="Windows10.MVVM.View.Demo1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:Windows10.MVVM.View"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
xmlns:vm="using:Windows10.MVVM.ViewModel1">
<Grid Background="Transparent">
<StackPanel Margin="10 0 10 10">
<!--
View 层
-->
<!--
本例通过 Binding 结合 Command 实现 MVVM（用 x:Bind 结合 Command 实现 MVVM 也是一样的），通过 ButtonBase 触发命令
-->
<StackPanel.DataContext>
<vm:ProductViewModel />
</StackPanel.DataContext>
<ListView Name="listView" ItemsSource="{Binding Products}" Width="300" Height="300" HorizontalAlignment="Left" VerticalAlignment="Top">
<ListView.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding Name}" HorizontalAlignment="Left" />
<TextBlock Text="{Binding Category}" HorizontalAlignment="Left" Margin="10 0 0 0" />
</StackPanel>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
<StackPanel Orientation="Horizontal" Margin="0 10 0 0" DataContext="{Binding Product}">
<TextBlock Text="Name：" VerticalAlignment="Center" />
<TextBox Name="txtName" Text="{Binding Name, Mode=TwoWay}" Width="100" />
<TextBlock Text="Category：" VerticalAlignment="Center" Margin="20 0 0 0" />
<TextBox Name="txtCategory" Text="{Binding Category, Mode=TwoWay}" Width="100" />
</StackPanel>
<!--
ButtonBase
Command - 指定关联的 ICommand
CommandParameter - 传递给 ICommand 的参数
-->
<StackPanel Orientation="Horizontal" Margin="0 10 0 0">
<Button Name="btnSearch" Content="查询" Command="{Binding GetProductsCommand}" Margin="10 0 0 0" />
<Button Name="btnAdd" Content="添加" Command="{Binding AddProductCommand}" Margin="10 0 0 0" />
<Button Name="btnUpdate" Content="更新" Command="{Binding UpdateProductCommand}" CommandParameter="{Binding SelectedItem, ElementName=listView}" Margin="10 0 0 0" />
<Button Name="btnDelete" Content="删除" Command="{Binding DeleteProductCommand}" CommandParameter="{Binding SelectedItem, ElementName=listView}" Margin="10 0 0 0" />
</StackPanel>
</StackPanel>
</Grid>
</Page>
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