.net - How is List<T>.IndexOf() implemented in C#?

Question

I was thinking about the performance of calling List<T>.Indexof(item). I am not sure if it will be a O(n) performance for a sequential algorithm or O(log(n)) performance for a binary tree??

Answer 1

Using Reflector for .NET we can see:

public int IndexOf(T item)
{
    return Array.IndexOf<T>(this._items, item, 0, this._size);
}

public static int IndexOf<T>(T[] array, T value, int startIndex, int count)
{
    return EqualityComparer<T>.Default.IndexOf(array, value, startIndex, count);
}

internal virtual int IndexOf(T[] array, T value, int startIndex, int count)
{
    int num = startIndex + count;
    for (int i = startIndex; i < num; i++)
    {
        if (this.Equals(array[i], value))
            return i;
    }
    return -1;
}