public int Capacity { get; set; }

can not be set lower than DynamicBuffer<T>.Length - this will raise an exception. If grows greater than the internal capacity of the DynamicBuffer, memory external to the DynamicBuffer will be allocated. If shrinks to the internal capacity of the DynamicBuffer or smaller, memory external to the DynamicBuffer will be freed. No effort is made to avoid costly reallocations when changes slightly; if is incremented by 1, an array 1 element bigger is allocated.