Namynnuz

public class SimpleSystemStack<T> where T : struct, IConvertible {
    private readonly int _sizeOfOneElement;
    private T[] _array;

    public SimpleSystemStack( int sizeOfOneElement, T[] inputArray = null ) {
        _sizeOfOneElement = sizeOfOneElement;
        if ( inputArray?.Length > 0 ) {
            Length = inputArray.Length;
            _array = inputArray;
        } else {
            Length = 0;
            _array = new T[sizeOfOneElement];
        }
    }

    public int Length { get; private set; }

    public T Pop() {
        if ( Length > 0 ) {
            Length--;
            return _array[Length];
        }
        throw new IndexOutOfRangeException("Stack is Empty.");
    }

    public void Push( T element ) {
        if ( Length >= int.MaxValue )
            throw new IndexOutOfRangeException("Stack overflow.");
        if ( Length >= _array.Length ) {
            var temp = new T[_array.Length * 2];
            Buffer.BlockCopy( _array, 0, temp, 0, Length * _sizeOfOneElement );
            _array = temp;
        }
        _array[Length] = element;
        Length++;        
    }
}

var sss = new SimpleSystemStack<int>( sizeof( int ) );

sss.Push( 1 );
sss.Push( 2 );
sss.Push( 3 );
sss.Pop();
sss.Pop();
sss.Push( 4 );