C# - How to Import data from multiple CSV or Text files to an Excel sheet in C#

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data.SqlClient;
using System.IO;
using System.Data.OleDb;


namespace TechBrothersIT.com_CSharp_Tutorial
{
class Program
    {
staticvoid Main(string[] args)
        {
//the datetime and Log folder will be used for error log file in case error occured
string datetime = DateTime.Now.ToString("yyyyMMddHHmmss");
string LogFolder = @"C:\Log\";
            try
            {

                //Declare Variables
                //Provide the Source folder path where input files exist
                string SourceFolderPath = @"C:\Source\";
                //Provide the destination folder path where you like to create Excel file
                string DestinationFolderPath = @"C:\Destination\";
                // Provide the extension of input files such as .txt or .csv
                string FileExtension = ".txt";
                // Provide the file delimiter such as comma or pipe
                string FileDelimiter = ",";
                // Provide the name of Excel file you like to create
                string ExcelFileName = "TechBrothersITCourses";
                string CreateTableStatement = "";
                string ColumnList = "";
                Int16 FileCnt = 0;

                //Reading file names one by one
                string SourceDirectory = SourceFolderPath;
                string[] fileEntries = Directory.GetFiles(SourceDirectory, "*" + FileExtension);
                foreach (string fileName in fileEntries)
                {


                    //Read first line(Header) and prepare Create Statement for Excel Sheet
                    System.IO.StreamReader file = new System.IO.StreamReader(fileName);
                    string filenameonly = (((fileName.Replace(SourceDirectory, "")).Replace(FileExtension, "")).Replace("\\", ""));
                    CreateTableStatement = (" Create Table [" + ExcelFileName + "] ([" + file.ReadLine().Replace(FileDelimiter, "] Text,[")) + "] Text,[CSVFileName] Text)";
                    file.Close();

                    //Construct ConnectionString for Excel, also adding date-time
                    string connstring = "Provider=Microsoft.ACE.OLEDB.12.0;" + "Data Source=" + DestinationFolderPath + "\\" + ExcelFileName + "_" + datetime
                        + ";" + "Extended Properties=\"Excel 12.0 Xml;HDR=YES;\"";
                    OleDbConnection Excel_OLE_Con = new OleDbConnection();
                    OleDbCommand Excel_OLE_Cmd = new OleDbCommand();

                    Excel_OLE_Con.ConnectionString = connstring;
                    Excel_OLE_Con.Open();
                    Excel_OLE_Cmd.Connection = Excel_OLE_Con;

//Create Sheet if does not exists
if (FileCnt == 0)
                    {
                        Excel_OLE_Cmd.CommandText = CreateTableStatement;
                        Excel_OLE_Cmd.ExecuteNonQuery();
                    }

//Writing Data of File to Excel Sheet in Excel File
int counter = 0;
string line;

                    System.IO.StreamReader SourceFile =
new System.IO.StreamReader(fileName);
                    while ((line = SourceFile.ReadLine()) != null)
                    {
if (counter == 0)
                        {
//I am also inserting CSV file name, if you don't like remove [CSVFileName]
                            ColumnList = "[" + line.Replace(FileDelimiter, "],[") + "],[CSVFileName]";

                        }
else
                        {
string query = "Insert into [" + ExcelFileName + "] (" +
                                ColumnList + ") VALUES('" +
                                line.Replace(FileDelimiter, "','") 
//if you don't want to insert file name , then remove the filename+FileExtension part
                                + "','" + filenameonly + FileExtension + "')";

var command = query;
                            Excel_OLE_Cmd.CommandText = command;
                            Excel_OLE_Cmd.ExecuteNonQuery();

                        }
                        counter++;
                    }
                    Excel_OLE_Con.Close();
                    SourceFile.Close();
                    FileCnt += 1;

                }
            }
catch (Exception exception)
            {
// Create Log File for Errors
using (StreamWriter sw = File.CreateText(LogFolder
                    + "\\" + "ErrorLog_" + datetime + ".log"))
                {
                    sw.WriteLine(exception.ToString());

                }

            }

        }
    }
}