Why Doesn't ObservableCollection Have an AddRange Method, and How Can I Add One?

ObservableCollection's Missing AddRange Functionality and a Workaround

The standard ObservableCollection in .NET doesn't include an AddRange method for adding multiple items simultaneously. This limitation can be cumbersome when dealing with large datasets or replacing the entire collection.

Creating a Custom ObservableRangeCollection

To address this, we can build a custom ObservableRangeCollection class extending ObservableCollection and incorporating the desired AddRange functionality. Here's how to implement this in C# and VB.NET:

C# Implementation:

using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;

namespace CustomCollections
{
    public class ObservableRangeCollection<T> : ObservableCollection<T>
    {
        public void AddRange(IEnumerable<T> collection)
        {
            if (collection == null) throw new ArgumentNullException(nameof(collection));

            foreach (var item in collection)
            {
                Items.Add(item);
            }
            OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
        }
    }
}

VB.NET Implementation:

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

Namespace CustomCollections
    Public Class ObservableRangeCollection(Of T)
        Inherits ObservableCollection(Of T)

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

            For Each item In collection
                Items.Add(item)
            Next
            OnCollectionChanged(New NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset))
        End Sub
    End Class
End Namespace

Utilizing the Custom Collection:

After creating the ObservableRangeCollection class, you can use it similarly to a standard ObservableCollection, but now with the added AddRange method:

var myCollection = new ObservableRangeCollection<int>();
myCollection.AddRange(new[] { 1, 2, 3, 4, 5 });

Dim myCollection As New ObservableRangeCollection(Of Integer)()
myCollection.AddRange({1, 2, 3, 4, 5})

Extending Functionality Further

This custom collection can be further enhanced by adding methods like RemoveRange, Replace, and ReplaceRange to provide even more comprehensive collection management capabilities.

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