How to Add an AddRange Method and INotifyCollectionChanging to an ObservableCollection in .NET?

The

class in .NET provides a dynamic collection of data that can be notified when items are added, removed, or rearranged. However, it lacks the ObservableCollection method, which cannot batch add multiple items at once. Additionally, the AddRange interface can be used to track changes before they are committed to the collection, providing the opportunity to cancel the changes. INotifyCollectionChanging

Here's how to implement the

method in ObservableCollection and integrate AddRange. INotifyCollectionChanging

C#:

using System;
using System.Collections.ObjectModel;
using System.Collections.Generic;
using System.Collections.Specialized;

public class ObservableRangeCollection<T> : ObservableCollection<T>, INotifyCollectionChanging<T>
{
    public event NotifyCollectionChangingEventHandler<T> CollectionChanging;

    protected override void OnCollectionChanging(NotifyCollectionChangingEventArgs e)
    {
        // 创建一个包含更改信息的事件参数
        var typedEventArgs = new NotifyCollectionChangingEventArgs<T>(e.Action, e.NewItems != null ? (IEnumerable<T>)e.NewItems : null, e.OldItems != null ? (IEnumerable<T>)e.OldItems : null, e.Index);

        // 触发自定义事件，允许取消操作
        CollectionChanging?.Invoke(this, typedEventArgs);

        // 检查是否取消
        if (typedEventArgs.Cancel)
        {
            return;
        }

        // 调用基类的OnCollectionChanging方法
        base.OnCollectionChanging(e);
    }

    public void AddRange(IEnumerable<T> collection)
    {
        if (collection == null)
        {
            throw new ArgumentNullException(nameof(collection));
        }

        // 触发CollectionChanging事件
        OnCollectionChanging(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, collection));

        // 添加项目
        foreach (T item in collection)
        {
            Add(item);
        }
    }
}

//自定义INotifyCollectionChanging接口，用于类型安全
public interface INotifyCollectionChanging<T> : INotifyCollectionChanged
{
    event NotifyCollectionChangingEventHandler<T> CollectionChanging;
}

//自定义事件处理程序，用于类型安全
public delegate void NotifyCollectionChangingEventHandler<T>(object sender, NotifyCollectionChangingEventArgs<T> e);

//自定义事件参数，用于类型安全
public class NotifyCollectionChangingEventArgs<T> : NotifyCollectionChangedEventArgs
{
    public NotifyCollectionChangingEventArgs(NotifyCollectionChangedAction action, IEnumerable<T> newItems) : base(action, newItems) { }
    public NotifyCollectionChangingEventArgs(NotifyCollectionChangedAction action, IEnumerable<T> newItems, IEnumerable<T> oldItems) : base(action, newItems, oldItems) { }
    public NotifyCollectionChangingEventArgs(NotifyCollectionChangedAction action, IEnumerable<T> newItems, int index) : base(action, newItems, index) { }
    public NotifyCollectionChangingEventArgs(NotifyCollectionChangedAction action, T newItem, int index) : base(action, newItem, index) { }
    public NotifyCollectionChangingEventArgs(NotifyCollectionChangedAction action, T oldItem, int index) : base(action, null, oldItem, index) { }
    public bool Cancel { get; set; }
}

VB.NET:

Imports System
Imports System.Collections.ObjectModel
Imports System.Collections.Generic
Imports System.Collections.Specialized
Imports System.ComponentModel

Public Class ObservableRangeCollection(Of T)
    Inherits ObservableCollection(Of T)
    Implements INotifyCollectionChanging(Of T)

    Public Event CollectionChanging As NotifyCollectionChangingEventHandler(Of T) Implements INotifyCollectionChanging(Of T).CollectionChanging

    Protected Overrides Sub OnCollectionChanging(e As NotifyCollectionChangedEventArgs)
        Dim typedEventArgs As New NotifyCollectionChangingEventArgs(Of T)(e.Action, If(e.NewItems IsNot Nothing, DirectCast(e.NewItems, IEnumerable(Of T)), Nothing), If(e.OldItems IsNot Nothing, DirectCast(e.OldItems, IEnumerable(Of T)), Nothing), e.Index)
        RaiseEvent CollectionChanging(Me, typedEventArgs)
        If typedEventArgs.Cancel Then
            Return
        End If
        MyBase.OnCollectionChanging(e)
    End Sub

    Public Sub AddRange(collection As IEnumerable(Of T))
        If collection Is Nothing Then
            Throw New ArgumentNullException("collection")
        End If

        OnCollectionChanging(New NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, collection))

        For Each item As T In collection
            Add(item)
        Next
    End Sub
End Class

'自定义INotifyCollectionChanging接口，用于类型安全
Public Interface INotifyCollectionChanging(Of T)
    Inherits INotifyCollectionChanged
    Event CollectionChanging As NotifyCollectionChangingEventHandler(Of T)
End Interface

'自定义事件处理程序，用于类型安全
Public Delegate Sub NotifyCollectionChangingEventHandler(Of T)(sender As Object, e As NotifyCollectionChangingEventArgs(Of T))

'自定义事件参数，用于类型安全
Public Class NotifyCollectionChangingEventArgs(Of T)
    Inherits NotifyCollectionChangedEventArgs
    Public Sub New(action As NotifyCollectionChangedAction, newItems As IEnumerable(Of T))
        MyBase.New(action, newItems)
    End Sub
    Public Sub New(action As NotifyCollectionChangedAction, newItems As IEnumerable(Of T), oldItems As IEnumerable(Of T))
        MyBase.New(action, newItems, oldItems)
    End Sub
    Public Sub New(action As NotifyCollectionChangedAction, newItems As IEnumerable(Of T), index As Integer)
        MyBase.New(action, newItems, index)
    End Sub
    Public Sub New(action As NotifyCollectionChangedAction, newItem As T, index As Integer)
        MyBase.New(action, newItem, index)
    End Sub
    Public Sub New(action As NotifyCollectionChangedAction, oldItem As T, index As Integer)
        MyBase.New(action, Nothing, oldItem, index)
    End Sub
    Public Property Cancel As Boolean
End Class

With this approach, you benefit from batch operations while being able to track and cancel changes before they occur. The code has been improved to make it more robust and handle type safety issues for

events. It also includes an override of the INotifyCollectionChanging method to ensure that after the custom event is triggered, the base class's OnCollectionChanging method is still called, thus ensuring the normal functionality of OnCollectionChanging. ObservableCollection

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