Sane multi-dimensional arrays in C#

Array2D.cs

using System;

namespace ArrayND
{
	public class Array2D<T>
	{
		private int m_width;
		private int m_height;
		private T[] m_data;

		public int Width  { get { return m_width;  } }
		public int Height { get { return m_height; } }

		public Array2D(int p_width, int p_height)
		{
			m_width  = p_width;
			m_height = p_height;
			m_data   = new T[p_width * p_height];
		}

		public T this[int x, int y]
		{
			get { SanityCheck(x, y); return m_data[y * m_width + x];  }
			set { SanityCheck(x, y); m_data[y * m_width + x] = value; }
		}

		private void SanityCheck(int p_x, int p_y)
		{
#if DEBUG
			if (p_x < 0 || p_x >= m_width || 
			    p_y < 0 || p_y >= m_height)
			{
				throw new IndexOutOfRangeException();
			}
#endif
		}
	}
}

Array3D.cs

using System;

namespace ArrayND
{
	public class Array3D<T>
	{
		private int m_width;
		private int m_height;
		private int m_depth;
		private T[] m_data;

		public int Width  { get { return m_width;  } }
		public int Height { get { return m_height; } }
		public int Depth  { get { return m_depth;  } }

		public Array3D(int p_width, int p_height, int p_depth)
		{
			m_width  = p_width;
			m_height = p_height;
			m_depth  = p_depth;
			m_data   = new T[p_width * p_height * p_depth];
		}

		public T this[int x, int y, int z]
		{
			get { SanityCheck(x, y, z); return m_data[(z * m_height + y) * m_width + x]; }
			set { SanityCheck(x, y, z); m_data[(z * m_height + y) * m_width + x] = value; }
		}

		private void SanityCheck(int p_x, int p_y, int p_z)
		{
			if (p_x < 0 || p_x >= m_width  ||
			    p_y < 0 || p_y >= m_height ||
			    p_z < 0 || p_z >= m_depth)
			{
				throw new IndexOutOfRangeException();
			}
		}
	}
}