StringCollection.cs

namespace System.Collections.Specialized
{
    [Serializable]
    public class StringCollection : IList, ICollection, IEnumerable
    {
        private ArrayList data = new ArrayList();

        public string this[int index]
        {
            get
            {
                return (string)data[index];
            }
            set
            {
                data[index] = value;
            }
        }

        public int Count => data.Count;

        bool IList.IsReadOnly
        {
            get
            {
                return false;
            }
        }

        bool IList.IsFixedSize
        {
            get
            {
                return false;
            }
        }

        public bool IsReadOnly => false;

        public bool IsSynchronized => false;

        public object SyncRoot => data.SyncRoot;

        object IList.this[int index]
        {
            get
            {
                return this[index];
            }
            set
            {
                this[index] = (string)value;
            }
        }

        public int Add(string value)
        {
            return data.Add(value);
        }

        public void AddRange(string[] value)
        {
            if (value == null)
            {
                throw new ArgumentNullException("value");
            }
            data.AddRange(value);
        }

        public void Clear()
        {
            data.Clear();
        }

        public bool Contains(string value)
        {
            return data.Contains(value);
        }

        public void CopyTo(string[] array, int index)
        {
            data.CopyTo(array, index);
        }

        public StringEnumerator GetEnumerator()
        {
            return new StringEnumerator(this);
        }

        public int IndexOf(string value)
        {
            return data.IndexOf(value);
        }

        public void Insert(int index, string value)
        {
            data.Insert(index, value);
        }

        public void Remove(string value)
        {
            data.Remove(value);
        }

        public void RemoveAt(int index)
        {
            data.RemoveAt(index);
        }

        int IList.Add(object value)
        {
            return Add((string)value);
        }

        bool IList.Contains(object value)
        {
            return Contains((string)value);
        }

        int IList.IndexOf(object value)
        {
            return IndexOf((string)value);
        }

        void IList.Insert(int index, object value)
        {
            Insert(index, (string)value);
        }

        void IList.Remove(object value)
        {
            Remove((string)value);
        }

        void ICollection.CopyTo(Array array, int index)
        {
            data.CopyTo(array, index);
        }

        IEnumerator IEnumerable.GetEnumerator()
        {
            return data.GetEnumerator();
        }
    }
}