read from excel file to datatable asp.net - asp.net

Question

I got this code to read from a excel file after uploading
public static DataTable getDataTableFromExcel(string path)
{
using (var pck = new OfficeOpenXml.ExcelPackage())
{
using (var stream = File.OpenRead(path))
{
pck.Load(stream);
}
var ws = pck.Workbook.Worksheets.First();
DataTable tbl = new DataTable();
bool hasHeader = true; // adjust it accordingly( i've mentioned that this is a simple approach)
foreach (var firstRowCell in ws.Cells[1, 1, 1, ws.Dimension.End.Column])
{
tbl.Columns.Add(hasHeader ? firstRowCell.Text : string.Format("Column {0}", firstRowCell.Start.Column));
}
var startRow = hasHeader ? 2 : 1;
for (var rowNum = startRow; rowNum <= ws.Dimension.End.Row; rowNum++)
{
var wsRow = ws.Cells[rowNum, 1, rowNum, ws.Dimension.End.Column];
var row = tbl.NewRow();
foreach (var cell in wsRow)
{
row[cell.Start.Column - 1] = cell.Text;
}
tbl.Rows.Add(row);
}
return tbl;
}
}
protected void Button1_Click(object sender, EventArgs e)
{
try
{
string filename = Path.GetFileName(FileUpload1.FileName);
FileUpload1.SaveAs(Server.MapPath("~/Uploader/") + filename);
err.Text = "Upload status: File uploaded!";
DataTable dt = getDataTableFromExcel(Server.MapPath("~/Uploader/") + filename);
GridView1.DataSource = dt;
GridView1.DataBind();
err.Text = dt.Rows[1].ToString();
}
catch (Exception ex)
{
err.Text = "Upload status: The file could not be uploaded. The following error occured: " + ex.Message;
}
}
but i cannot understand it well ... if you could give me a little description about it ?
and how to read specific column
I need to read just the first and third and fifth column not all ... how to do that ?