How to compare excel sheets?

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C#

Hi,

I have code to read excel file and save them into dataset.
Now I need to read 3 excel files like this and I need to compare the message ID in the 3 excel files,for the common message ID.

I am attaching a image to show how my data in dataset looks like

Is it better to convert the table of message ID to list<t> before doing it?

using System;

using System.Data;
using System.Data.OleDb;
using System.Collections.Generic;
using System.Text;


namespace Excelcalling1
{
	class Program
	{
		static void Main(string[] args)
		{
			string ConnectionString = @"Provider=Microsoft.Jet.OLEDB.4.0;
					Data Source=E:\SheetForTest.xls;Integrated Security=SSPI;
					Extended Properties=Microsoft Excel 11.0 Object Library";

			//Create the connection

			System.Data.OleDb.OleDbConnection ExcelConnection =
			new System.Data.OleDb.OleDbConnection
							 (ConnectionString);

			//create a string for the query

			string ExcelQuery;

			//Sheet1 is the sheet name
			//create the query:
			//read column with heading A from the Excel file

			ExcelQuery = "Select A from [Sheet1$]"; // from Sheet1";

			//use "Select * ... " to select the entire sheet
			//create the command

			System.Data.OleDb.OleDbCommand ExcelCommand = new System.Data.OleDb.OleDbCommand(ExcelQuery, ExcelConnection);

			//Open the connection

			//ExcelConnection.Open();
			try
			{
				ExcelConnection.Open();
			}
			catch (OleDbException e)
			{
				string errorMessages = "";

				for (int i = 0; i < e.Errors.Count; i++)
				{
					errorMessages += "Index #" + i + "\n" +
									 "Message: " + e.Errors[i].Message + "\n" +
									 "NativeError: " + e.Errors[i].NativeError + "\n" +
									 "Source: " + e.Errors[i].Source + "\n" +
									 "SQLState: " + e.Errors[i].SQLState + "\n";
				}

				System.Diagnostics.EventLog log = new System.Diagnostics.EventLog();
				log.Source = "My Application";
				log.WriteEntry(errorMessages);
				Console.WriteLine("An exception occurred. Please contact your system administrator.");
			}

			//Create a reader

			System.Data.OleDb.OleDbDataReader ExcelReader;
			ExcelReader = ExcelCommand.ExecuteReader();

			//For each row after the first
			//Message box the values in the first column i.e. column 0

			while (ExcelReader.Read())
			{
				//MessageBox.Show((ExcelReader.GetValue(0)).ToString());
				Console.WriteLine("value retrieved!!");
			}
			ExcelConnection.Close();

			
		}
	}
}

Thanks
John