WPF入门教程系列二十八 ——DataGrid使用示例MVVM模式(6)

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摘要

WPF入门教程系列五——Window 介绍 7.上面Buttom的Command类就是纯命令,什么参数都不接收,这次的ProvinceChangedCommand类在执行命令的时候,能够传参数!采用泛型的形式,给Action添加泛型参数。

WPF入门教程系列五——Window 介绍

 
 
 

八、在Command中传递参数

7.上面Buttom的Command类就是纯命令,什么参数都不接收,这次的ProvinceChangedCommand类在执行命令的时候,能够传参数!采用泛型的形式,给Action添加泛型参数。

8. 在Visual Studio 2022的解决方案资源管理器中,使用鼠标右键单击“Command”文件夹,在弹出菜单中选择“添加--> 类”,在弹出的“添加新项”对话框中,选择添加 “ProvinceChangedCommand”类,这是一个我们要实现的保存操作指令,然后选择“添加”。ProvinceChangedCommand的具体代码如下:

using System; using System.Collections.Generic; using System.Linq; using System.Text;  using System.Threading.Tasks; using System.Windows.Input;   namespace WpfGridDemo.NET7.Command {     public class ProvinceChangedCommand<T> : ICommand     {         /// <summary>         /// 命令能否执行         /// </summary>         readonly Func<bool> _canExecute;         /// <summary>         /// 命令执行的方法         /// </summary>         readonly Action<T> _execute;           /// <summary>         /// 命令的构造函数         /// </summary>         /// <param name="action">命令需执行的方法</param>         /// <param name="canExecute">命令是否可以执行的方法</param>         public ProvinceChangedCommand(Action<T> action, Func<bool> canExecute)         {             _execute = action;             _canExecute = canExecute;         }           /// <summary>         /// 判断命令是否可以执行         /// </summary>         /// <param name="parameter"></param>         /// <returns></returns>         public bool CanExecute(Object parameter)         {             if (_canExecute == null)                 return true;             return _canExecute();         }           /// <summary>         /// 执行命令         /// </summary>         /// <param name="parameter"></param>         public void Execute(Object parameter)         {             _execute((T)parameter);         }           /// <summary>         /// 事件追加、移除         /// </summary>         public event EventHandler CanExecuteChanged         {             add             {                 if (_canExecute != null)                     CommandManager.RequerySuggested += value;             }             remove             {                 if (_canExecute != null)                     CommandManager.RequerySuggested -= value;             }         }       } } void ProviceSelectionChangedExecute(object sender)         {             try             {                 if (sender is ComboBox)                 {                     ComboBox drp=sender as ComboBox;                     ProvinceCode=drp.SelectedValue.ToString();                     GridDbContext db = new GridDbContext();                     var list = db.City.AsTracking().ToList();                     List<City> citys = list.Where(x => x.ProvinceCode == ProvinceCode).ToList();                     cityList = new ObservableCollection<City>();                     if (citys != null)                     {                         citys.ForEach((t) =>                           { cityList.Add(t); }                         );                     }                       var cityCodes = from city in citys                                     select city.Code;                     List<Area> areas = db.Area.AsTracking().ToList().Where(
x => cityCodes.Contains(x.CityCode)).ToList(); areaList = new ObservableCollection<Area>(); if (areas!=null) { areas.ForEach((t) => { areaList.Add(t); } ); } } } catch (Exception ex) { throw ex; } }

结果如图:我们看到了省份下拉框中已经了省份信息。

WPF入门教程系列二十八 ——DataGrid使用示例MVVM模式(6)

 

9.通过绑定依赖属性,实现自动刷新需要实现以下三步:

1.Model继承并实现 INotifyPropertyChanged 接口;

2.数据集合使用ObservableCollection<T>集合;

3.View使用Binding数据对象属性;

如果不行再看看集合在赋值前需要实例化,不然就出不来(必须要同一个源才行)

10. 在Visual Studio 2022中打开MainWindows.xmal文件,并将文件中的代码修改成如下:

<Window x:Class="WpfGridDemo.NET7.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:be="http://schemas.microsoft.com/xaml/behaviors"         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"         xmlns:local="clr-namespace:WpfGridDemo.NET7"         mc:Ignorable="d"         Title="MainWindow" Height="600" Width="960" Loaded="Window_Loaded" >     <Grid>         <Grid.RowDefinitions>             <RowDefinition Height="100"></RowDefinition>             <RowDefinition Height="*"></RowDefinition>             <RowDefinition Height="25"></RowDefinition>         </Grid.RowDefinitions>         <WrapPanel Grid.Row="0" HorizontalAlignment="Left">             <ComboBox x:Name="cboProvince" DisplayMemberPath="Name" SelectedValuePath="Code" >                   <be:Interaction.Triggers>                      <be:EventTrigger EventName="SelectionChanged">                         <be:InvokeCommandAction Command="{Binding ProviceChangedAction}" 
CommandParameter
="{Binding ElementName=cboProvince}"/> </be:EventTrigger> </be:Interaction.Triggers> </ComboBox> </WrapPanel> <DataGrid x:Name="gridArea" Grid.Row="1" ItemsSource="{Binding GridAreaList}"
AutoGenerateColumns
="False" HorizontalAlignment="Left" VerticalAlignment="Top"
SelectedItem
="{Binding Path=AreaVM, Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"> <DataGrid.Columns> <DataGridComboBoxColumn Header="城市" Width="120"
ItemsSource
="{Binding Path=DataContext.GridCityList,
RelativeSource={RelativeSource AncestorType={x:Type Window}}}
"
x:Name
="cboCity" ClipboardContentBinding="{x:Null}"
SelectedValuePath="Code" SelectedValueBinding="{Binding Path=CityCode,
UpdateSourceTrigger=PropertyChanged}
"
DisplayMemberPath
="Name" SelectedItemBinding="{x:Null}" /> <DataGridTextColumn Header="县区镇" Width="*" Binding="{Binding Name}"
ClipboardContentBinding
="{x:Null}"/> <DataGridTextColumn Header="邮编" Width="100" Binding="{Binding Code}"
ClipboardContentBinding
="{x:Null}"/> <DataGridTextColumn Header="创建时间" Width="160" Binding="{Binding Created}"
ClipboardContentBinding
="{x:Null}"/> <DataGridTextColumn Header="更新时间" Width="160" Binding="{Binding Updated}"
ClipboardContentBinding
="{x:Null}"/> </DataGrid.Columns> </DataGrid> <WrapPanel Grid.Row="2"> <Button x:Name="btnRefresh" Height="22" Width="120" Click="btnRefresh_Click">刷新</Button> <Button x:Name="btnSave" Height="22" Width="120" Command="{Binding ClickSaveAction}" >保存</Button> </WrapPanel> </Grid> </Window>

 

11. 在Visual Studio 2022中打开MainWindowsVM.cs文件,实现下拉框的选择事件的Command命令绑定,将通过Command参数传递过来的省份信息,用于数据查询,同时通知UI界面进行数据刷新。具体如下代码:
using Microsoft.EntityFrameworkCore; using System; using System.Collections.Generic; using System.Collections.ObjectModel; using System.ComponentModel; using System.DirectoryServices.ActiveDirectory; using System.Linq; using System.Text; using System.Threading.Tasks; using System.Windows.Controls; using System.Windows.Input; using WpfGridDemo.NET7.Entitys;   namespace WpfGridDemo.NET7.ViewModel {     public class MainWindowVM: ViewModelBase     {         public MainWindowVM() {             cityList = new ObservableCollection<City>();             areaList = new ObservableCollection<Area>();         }         private Area m_Area;         /// <summary>         /// 县镇区数据         /// </summary>         public Area AreaVM         {             get { return m_Area; }             set { m_Area = value; }         }         private string m_Province_Code;         /// <summary>         /// 省--代码         /// </summary>         public string ProvinceCode { get => m_Province_Code; set => m_Province_Code = value; }         private ObservableCollection<Area> areaList;            public ObservableCollection<Area> GridAreaList          {              get { return areaList; }              set              {                 areaList = value;                  RaisePropertyChanged("GridAreaList");              }         }         private ObservableCollection<City> cityList;           public ObservableCollection<City> GridCityList         {             get { return cityList; }             set             {                 cityList = value;                 RaisePropertyChanged("GridCityList");             }         }              /// <summary>         /// 命令要执行的方法         /// </summary>         void SaveExecute()         {             try               {                 GridDbContext db = new GridDbContext();                 var list=db.Area.AsTracking().ToList();                 Area modifyArea = list.Where(x=>x.Id==AreaVM.Id).FirstOrDefault();                 if (modifyArea != null)                 {                     modifyArea.Name = AreaVM.Name;                     modifyArea.Updated = DateTime.Now;                     db.SaveChanges();                 }               }             catch (Exception ex)             {                   throw ex;             }         }           /// <summary>         /// 命令是否可以执行         /// </summary>         /// <returns></returns>         bool CanSaveExecute()         {             return false;         }           /// <summary>         /// 创建新命令         /// </summary>         public ICommand ClickSaveAction         {             get             {                 return new Command.SaveCommand(SaveExecute, CanSaveExecute);             }         }         //combobox         /// <summary>         /// 命令要执行的方法         /// </summary>         void ProviceSelectionChangedExecute(object sender)         {             try               {                 if (sender is ComboBox)                 {                     ComboBox drp=sender as ComboBox;                     ProvinceCode=drp.SelectedValue.ToString();                     GridDbContext db = new GridDbContext();                     var list = db.City.AsTracking().ToList();                      List<City> citys = list.Where(x => x.ProvinceCode == ProvinceCode).ToList();                     var cityCodes = from city in citys                                     select city.Code;                     List<Area> areas = db.Area.AsTracking().ToList().Where(
x => cityCodes.Contains(x.CityCode)).ToList(); areaList.Clear(); if (areas!=null) { areas.ForEach((t) => { areaList.Add(t); } ); } cityList.Clear(); if (citys != null) { citys.ForEach((t) => { cityList.Add(t); } ); } } } catch (Exception ex) { throw ex; } } /// <summary> /// 命令是否可以执行 /// </summary> /// <returns></returns> bool CanSelectionChangedExecute() { return true; } /// <summary> /// 创建新命令 /// </summary> public ICommand ProviceChangedAction { get { return new Command.ProvinceChangedCommand<object>(ProviceSelectionChangedExecute, CanSelectionChangedExecute); } } }

12.在Visual Studio 2022中按F5键,启动WPF应用程序。然后使用鼠标点击省份下拉框,能够看到,界面中DataGrid中的数据,随着下拉框的变化而随之变化。如下图。

WPF入门教程系列二十八 ——DataGrid使用示例MVVM模式(6)