add matrix data and stored it in 2-dimensional array in c#

Question

hi, i need help on to receive input from user and stored it in array. i already tru to code  but it does not return result, and display result. can someone help me. thank you.

input: 3,4

          8,2

          6,7

listbox2 : place to insert input matrix

listbox1 : to display input matrix

btnAdd : to add input matrix and stored in nums array

btnCompute : to compute the average , variance result

here is my code;

 using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace Mahalanobis_Distance
{
  public partial class Form1 : Form
  {
    private int[,] nums;
    private int _count = 0;
    int x, y;   
    

    public Form1()
    {
      InitializeComponent();
    }

    private void listBox2_KeyPress(object sender, KeyPressEventArgs e)
    {
      if (!Char.IsDigit(e.KeyChar) && e.KeyChar != Char.Parse(","))
        e.Handled = true;
    }


    // Compute and display result
    private void btnCompute_Click(object sender, EventArgs e)
    {
     
      meanX1.Text = AverageX(nums).ToString();
      variance.Text = varianceX(nums).ToString();
     // stdDev.Text = stdDeviationOfX;
    }
        
         
   // Calculate standard Deviation Value
   private double stdDeviation (double varianceX)
   {
    
    double stdDevX = Math.Sqrt(varianceX);
    return stdDevX;   

   }


    // Calculate Variance Value
    private double varianceX(int[,] nums)

    { 
      int NumMatrix =0;
      double varX =0;
      double sumSquare=0;
     

      // Get the Means@Average of X values  
      double avgX = AverageX(nums);
      // Declare the total Matrix
      NumMatrix = nums.Length;
      
      // Calculate the variance   
       
      for (int i = 0; i <= NumMatrix; i++)
        {
          sumSquare += Math.Pow((double)nums[i, 0]- avgX, 2);
        }
          varX= sumSquare/NumMatrix;
          return varX;    
        
    }

    
    // Average value of X matrik
    private double AverageX(int[,] nums)
    {

    double avgValueX = 0;
    double sumValueX = 0;
    

    for (int i = 0; i <=nums.GetUpperBound(0); i++) 
        {
         // Total Value Matrix X
          sumValueX += (double)nums[i, 0];
             
        }
                   
           avgValueX = sumValueX / (nums.GetUpperBound(0) + 1);
           return avgValueX;

     }
  
   
  
    // insert input matrix example (7,8) in listBox and stored in 2-dimensional array

    private void btnAdd_Click(object sender, EventArgs e)
    {
      nums = new int[listBox2.Items.Count, 2];
      
      for (int i = 0; i < this.listBox2.Items.Count; i++)
      {
        if (_count < 20 && this.listBox2.Items[i].ToString() != "" && this.listBox2.Items[i].ToString().Contains(","))
        {
          string t = this.listBox2.Items[i].ToString();

          string sx = t.Substring(0, t.IndexOf(","));
          Int32.TryParse(sx, out x);

          t = t.Substring(t.IndexOf(",") + 1);
          Int32.TryParse(t, out y);


          this.nums[_count, 0] = x;
          this.nums[_count, 1] = y;

          _count++;
                   
        }
      }
      
    }

    

    // Show input matrix in ListBox2
    private void showMatrixList(int[,] nums)
    {    
      for (int i = 0; i < listBox2.Items.Count; i++)
      {
        this.listBox1.Items.Add("X:" + x.ToString() + "; Y:" + y.ToString());
      }
    }
   


  }
}

really appreciate for the help