C# MAUI 快速批量更新 ObservableCollection 變數 【避免clear 和 Add 操作 都會導致 UI 重新繪製】 範例

資料來源: Copilot

01.建立模型類別：

public class Person
{
    public string Name { get; set; }
    public int Age { get; set; }
}

02.在 UI 中綁定 ObservableCollection：

<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="YourNamespace.MainPage">
    <StackLayout>
        <Button Text="Update People" Clicked="OnUpdatePeopleClicked" />
        <ListView ItemsSource="{Binding People}">
            <ListView.ItemTemplate>
                <DataTemplate>
                    <TextCell Text="{Binding Name}" Detail="{Binding Age}" />
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>
    </StackLayout>
</ContentPage>

03.擴展 ObservableCollection：

public class BulkObservableCollection<T> : ObservableCollection<T>
{
    private bool _suppressNotification = false;

    protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
    {
        if (!_suppressNotification)
        {
            base.OnCollectionChanged(e);
        }
    }

    public void AddRange(IEnumerable<T> items)
    {
        _suppressNotification = true;
        foreach (var item in items)
        {
            Add(item);
        }
        _suppressNotification = false;
        OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
    }

    public void ClearAndAddRange(IEnumerable<T> items)
    {
        _suppressNotification = true;
        Clear();
        foreach (var item in items)
        {
            Add(item);
        }
        _suppressNotification = false;
        OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
    }
}

04.使用 BulkObservableCollection： (重點在註解之上)

public ObservableCollection<Person> People { get; set; }//宣告時使用ObservableCollection

public MainPage()
{
    InitializeComponent();
    People = new BulkObservableCollection<Person>
    {
        new Person { Name = "Alice", Age = 30 },
        new Person { Name = "Bob", Age = 25 },
        new Person { Name = "Charlie", Age = 22 }
    }; //new 時 要使用BulkObservableCollection來建立物件

    BindingContext = this;
}

public void UpdatePeople()
{
    var updatedPeople = new List<Person>
    {
        new Person { Name = "David", Age = 35 },
        new Person { Name = "Eva", Age = 28 },
        new Person { Name = "Frank", Age = 24 }
    };

    ((BulkObservableCollection<Person>)People).ClearAndAddRange(updatedPeople);//更新資料語法
}

重點再次整理:

    宣告時使用ObservableCollection

    new 時 要使用BulkObservableCollection來建立物件