Make a C# function?

First, ask your teacher why you'd want an average function to return an integer. That seems like a poor decision. Rarely would you end up with an average that worked out to a whole number. Wouldn't you'd want it to be:

double AvgAoA(int [][]array);

Anyway, I'll work on that premise that your average shouldn't be an integer. On to the function itself. Simply use the SelectMany to make the 2D array elements into a 1D one, and average that:

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

using System.Windows.Forms;

namespace _2DAverage

{

public partial class Form1 : Form

{

public Form1()

{

InitializeComponent();

}

private void button1_Click(object sender, EventArgs e)

{

int[][] a = { new[] { 1, 2 }, new[] { 5 }, new[] { 9, 8, 7, 6 } };

MessageBox.Show(AvgAoA(a).ToString());

}

double AvgAoA(int[][] array)

{

int[] flattenedArray = array.SelectMany(a => a).ToArray();

return flattenedArray.Average();

}

}

}