WPF MVVMToolkit框架學習-ObservableObject

今天學習 ObservableObject的 三種綁定方式

1. 普通屬性的綁定

和常用的綁定沒有區別；

        private string _name;

        public string Name
        {
            get => _name;
            set => SetProperty(ref _name, value);
        }

源碼

        protected bool SetProperty<T>([NotNullIfNotNull("newValue")] ref T field, T newValue, [CallerMemberName] string? propertyName = null)
        {
            if (EqualityComparer<T>.Default.Equals(field, newValue))
            {
                return false;
            }

            OnPropertyChanging(propertyName);
            field = newValue;
            OnPropertyChanged(propertyName);
            return true;
        }

可以看到是先判定了是否相等然后再通知！

 

1. 數據代理屬性的綁定

    public class User
    {
        public int Age { get; set; }
    }

        private User _user;

        public int Age
        {
            get => _user.Age;
            set => SetProperty(_user.Age, value, _user, (u, a) => u.Age = a);
        }

可以看到 VM里面的屬性包裝了數據代理模型，通過委托來更新數據代理的數據；

源碼

        protected bool SetProperty<TModel, T>(T oldValue, T newValue, TModel model, Action<TModel, T> callback, [CallerMemberName] string? propertyName = null) where TModel : class
        {
            if (EqualityComparer<T>.Default.Equals(oldValue, newValue))
            {
                return false;
            }

            OnPropertyChanging(propertyName);
            callback(model, newValue);
            OnPropertyChanged(propertyName);
            return true;
        }

 

1. Task屬性的綁定

        private TaskNotifier<int> _count;
        /// <summary>
        /// 任務屬性綁定
        /// </summary>
        public Task<int> Count
        {
            get => _count;
            set => SetPropertyAndNotifyOnCompletion(ref _count, value);
        }
        public ICommand RequestValueCmd { get; set; }

        private async void RequestValue()
        {
            await Task.Delay(5000);
            Count = Task.Run(() =>
            {
                return 50;
            });
        }

可以實現任務完成后自動刷新UI

 源碼

        protected bool SetPropertyAndNotifyOnCompletion([NotNull] ref TaskNotifier? taskNotifier, Task? newValue, [CallerMemberName] string? propertyName = null)
        {
            return SetPropertyAndNotifyOnCompletion(taskNotifier ?? (taskNotifier = new TaskNotifier()), newValue, delegate
            {
            }, propertyName);
        }

 

后台代碼

using Microsoft.Toolkit.Mvvm.ComponentModel;
using Microsoft.Toolkit.Mvvm.Input;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Input;

namespace MVVMToolkit學習
{
    public class ObservableObjectVM : ObservableObject
    {


        #region 普通屬性綁定
        private string _name;

        public string Name
        {
            get => _name;
            set => SetProperty(ref _name, value);
        }
        #endregion

        #region 數據代理綁定
        private User _user;

        public int Age
        {
            get => _user.Age;
            set => SetProperty(_user.Age, value, _user, (u, a) => u.Age = a);
        }

        #endregion



        public ObservableObjectVM()
        {
            Name = "嘯天";
            _user = new User();
            _user.Age = 18;
            RequestValueCmd = new RelayCommand(RequestValue);
        }


        #region 綁定任務屬性 
        private TaskNotifier<int> _count;
        /// <summary>
        /// 任務屬性綁定
        /// </summary>
        public Task<int> Count
        {
            get => _count;
            set => SetPropertyAndNotifyOnCompletion(ref _count, value);
        }
        public ICommand RequestValueCmd { get; set; }

        private async void RequestValue()
        {
            await Task.Delay(5000);
            Count = Task.Run(() =>
            {
                return 50;
            });
        }
        #endregion
    }

    public class User
    {
        public int Age { get; set; }
    }
}

前台代碼

<Window
    x:Class="MVVMToolkit學習.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:local="clr-namespace:MVVMToolkit學習"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    Title="MainWindow"
    Width="800"
    Height="450"
    d:DataContext="{d:DesignInstance Type=local:ObservableObjectVM}"
    mc:Ignorable="d">
    <Grid>
        <StackPanel
            MinWidth="300"
            HorizontalAlignment="Center"
            Orientation="Vertical">
            <TextBlock Text="{Binding Name}" />
            <TextBox Text="{Binding Age}" />
            <TextBlock Text="{Binding Count.Result, UpdateSourceTrigger=PropertyChanged}" />
            <Button
                Command="{Binding RequestValueCmd}"
                Content="延時綁定" />
        </StackPanel>
    </Grid>
</Window>