<PackageReference Include="System.Configuration.ConfigurationManager" Version="10.0.2" />

System.Configuration.CommaDelimitedStringCollection

Represents a collection of string elements separated by commas. This class cannot be inherited.
namespace System.Configuration { public sealed class CommaDelimitedStringCollection : StringCollection { public bool IsModified { get; } public new bool IsReadOnly { get; } public new string this[int index] { get; set; } public CommaDelimitedStringCollection(); public void SetReadOnly(); public new void Add(string value); public new void AddRange(string[] range); public new void Clear(); public new void Insert(int index, string value); public new void Remove(string value); public CommaDelimitedStringCollection Clone(); } }