Object reference not set to an instance of an object on GetLenght() [duplicate]

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What is a NullReferenceException, and how do I fix it? (26 answers)

Closed 9 years ago.

I have a app that reads data from Excel xlsx file to 2D array. Now I would like to sum all values in every row on a button click. First I am trying to get length of each dimension of that array. On this point I am getting error:

 Object reference not set to an instance of an object

Can you suggest what to do to avoid this error? 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;
  using Excel = Microsoft.Office.Interop.Excel;
  using System.Reflection;

  namespace WindowsFormsApplication2
  {
    public partial class Form1 : Form, IDisposable
  {
     public Form1()
     {
       InitializeComponent();
     }

    string[,] tsReqs;

    private void button1_Click(object sender, EventArgs e)
     {
        Excel.Application xlApp = new Excel.Application();
        Excel.Workbook xlWorkbook = xlApp.Workbooks.Open(@"C:/test.xlsx");
        Excel._Worksheet xlWorksheet = xlWorkbook.Sheets[1];
        Excel.Range xlRange = xlWorksheet.UsedRange;

        int rowCount = xlRange.Rows.Count;
        int colCount = xlRange.Columns.Count;


        string[,] tsReqs = new string[rowCount, colCount];
        for (int i = 1; i <= rowCount; i++)
        {
            for (int j = 1; j <= colCount; j++)
            {
                string str = xlRange.Cells[i, j].Text;
                tsReqs[i - 1, j - 1] = str;
            }
        }

    }

    private void button3_Click(object sender, EventArgs e)
    {
        int riadky = tsReqs.GetLength(0);
        int stlpce = tsReqs.GetLength(1);
        double sucet = 0;

        for (int i = 1; i <= riadky; i++)
        {
            for (int j = 1; j <= stlpce; j++)
            {
                double hodnota = Convert.ToDouble(tsReqs[i, j]);
                sucet = sucet + hodnota;
            }

            richTextBox1.Text = sucet.ToString()+"\n";
             }
         }
     }
 }

Answer 1

You have global variable: string[,] tsReqs;

and have local variable:

 private void button1_Click(object sender, EventArgs e)
 {
   .....

    //This is NOT global variable initilization!!!!!!
    string[,] tsReqs = new string[rowCount, colCount];
    //.....
    for (int i = 1; i <= rowCount; i++)
    {...
    }

}

So on your button1 click you initialize local variable, but on button3 click you refer to global variable.