Read Data from Excel Sheet in C#, .NET

Question

Excel Data reader read data from Excel sheet in order compare it with the UI dropdown values and see if they exists

I am trying to read data from excel sheet using below code

// methods to read data and parse the data into populate collection

using ExcelDataReader;
using System;
using System.Collections.Generic;
using System.Data;
using System.IO;
using System.Linq;

namespace GorillaUITests.PageObjects
{
    public class ExcelRead
    {
        public static List<Datacollection> dataCol = new List<Datacollection>();

        public static DataTable ExcelToDataTable(string fileName)
        {
            using (var stream = File.Open(fileName, FileMode.Open, FileAccess.Read))
            {
                using (var reader = ExcelReaderFactory.CreateReader(stream))
                {
                    var result = reader.AsDataSet(new ExcelDataSetConfiguration()

                    {
                        UseColumnDataType = true,

                        ConfigureDataTable = (data) => new ExcelDataTableConfiguration()
                        {
                            UseHeaderRow = true
                        }
                    });

                    //Get all the Tables
                    DataTableCollection table = result.Tables;
                    //Store it in DataTable
                    DataTable resultTable = table["Sheet1"];
                    //return
                    return resultTable;
                }
            }
        }
        public static void PopulateInCollection(string fileName)
        {
            DataTable table = ExcelToDataTable(fileName);

            //Iterate through the rows and columns of the Table
            for (int row = 1; row <= table.Rows.Count; row++)
            {
                for (int col = 0; col < table.Columns.Count; col++)
                {
                    Datacollection dtTable = new Datacollection()
                    {
                        rowNumber = row,
                        colName = table.Columns[col].ColumnName,
                        colValue = table.Rows[row - 1][col].ToString()
                    };
                    //Add all the details for each row
                    dataCol.Add(dtTable);
                }
            }
        }

        /// <summary>
        /// Read data from Collection
        /// </summary>
        /// <param name="rowNumber"></param>
        /// <param name="columnName"></param>
        /// <returns></returns>
        public static string ReadData(int rowNumber, string columnName)
        {
            try
            {
                //Retriving Data using LINQ to reduce much of iterations
                string data = (from colData in dataCol
                               where colData.colName == columnName && colData.rowNumber == rowNumber
                               select colData.colValue).SingleOrDefault();

                //var datas = dataCol.Where(x => x.colName == columnName && x.rowNumber == rowNumber).SingleOrDefault().colValue;
                return data.ToString();
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
                return null;
            }
        }


    }

    public class Datacollection
    {
        public int rowNumber { get; set; }
        public string colName { get; set; }

        public string colValue { get; set; }
    }
}

// Test to see if we are able to read data

public void ReadDataFromExcel(string user, string pass)
        {
            // populate data in collection

            try
            {
                ExcelRead.PopulateInCollection(@"C:\Users\username\Documents\GorillaUITests\GorillaUITests\Tests\Data\ReadDataTest.xlsx");

                Debug.WriteLine("UserName:" + ExcelRead.ReadData(1, "UserName"));
                Debug.WriteLine("Email:" + ExcelRead.ReadData(1, "Email"));
                Debug.WriteLine("***********");
                Debug.WriteLine("UserName:" + ExcelRead.ReadData(2, "UserName"));
                Debug.WriteLine("Email:" + ExcelRead.ReadData(2, "Email"));
                Debug.WriteLine("***********");
                Debug.WriteLine("Username:" + ExcelRead.ReadData(2, "UserName"));
                Debug.WriteLine("Email:" + ExcelRead.ReadData(2, "Email"));
                Debug.WriteLine("***********");
                           
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
            }

And I see this error below

“Object reference not set to an instance of an object.”

Not sure what I am missing, Any inputs would be appreciated