Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

C# C# Collections Arrays Multidimensional Arrays

Fredrik Rönnehag
Fredrik Rönnehag
2,342 Points
Posted by Fredrik Rönnehag
Fredrik Rönnehag
2,342 Points

Looping through a 3D jagged array

Trying to follow the example for the jagged array, but I'm getting NullReferenceException for my second for loop.

            Cell[][][] threeDimensions = new Cell[100][][];

            for (int i = 0; i < threeDimensions.Length; i++)
            {
                threeDimensions[i] = new Cell[10][];

                for (int y = 0; y < threeDimensions[i].Length; y++)
                {
                    threeDimensions[i][y] = new Cell[10];

                    for (int x = 0; x < threeDimensions[x].Length; x++)
                    {
                        threeDimensions[i][y][x] = new Cell();
                    }
                }
            }
Steven Parker
Steven Parker
229,732 Points
Steven Parker
Steven Parker
229,732 Points

It would be easier to analyze the issue with the entire project. To share that, make a snapshot of your workspace and post the link to it here.

Fredrik Rönnehag
Fredrik Rönnehag
2,342 Points
Fredrik Rönnehag
Fredrik Rönnehag
2,342 Points

I did it in Visual Studios rather than workspace. I actually noticed the problem and fixed it myself, leaving the code here if someone else gets stuck :)

namespace Collections
{
    class Program
    {
        static void Main(string[] args)
        {
            Cell[][][] threeDimensions = new Cell[100][][];

            for (int i = 0; i < threeDimensions.Length; i++)
            {
                threeDimensions[i] = new Cell[10][];

                for (int y = 0; y < threeDimensions[i].Length; y++)
                {
                    threeDimensions[i][y] = new Cell[10];

                    for (int x = 0; x < threeDimensions[i][y].Length; x++)
                    {
                        threeDimensions[i][y][x] = new Cell();
                    }
                }
            }
     }

    class Cell
    {
        public string Contents { get; set; }
    }



}

1 Answer

Steven Parker
Steven Parker
229,732 Points
Steven Parker
Steven Parker
229,732 Points

For the benefit of anyone who doesn't immediately spot the difference, the innermost "for" loop is missing a dimension and has an incorrect index in the conditional clause:

                    for (int x = 0; x < threeDimensions[x].Length; x++)     // original
                    for (int x = 0; x < threeDimensions[i][y].Length; x++)  // fixed