Change default column header while importing data

I have a gridview which has 4 columns in total now the first column name i am importing from an excel sheet which is named as "FileName".the gridview is taking columnheader name by default as F1 instead of filename.i need that f1 to be replaced with my column header name which is "filename"

shared the image please check : https://snag.gy/Y0V8CZ.jpg

by this function

public DataTable ReadExcel(string fileName, string fileExt)
{
string conn = string.Empty;
DataTable dtexcel = new DataTable();
if (fileExt.CompareTo(".xls") == 0)
conn = @"provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + fileName + ";Extended Properties='Excel 8.0;HRD=Yes;IMEX=1';"; //for below excel 2007
else
conn = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + fileName + ";Extended Properties='Excel 12.0;HDR=NO';"; //for above excel 2007
using (OleDbConnection con = new OleDbConnection(conn))
{
try
{
OleDbDataAdapter oleAdpt = new OleDbDataAdapter("select * from [Sheet$]", con); //here we read data from sheet1
oleAdpt.Fill(dtexcel); //fill excel data into dataTable

}
catch { }
}
return dtexcel;
}

for both extensions xls and xlsx on a button click i am comparing both extensions

private void btnimport_Click(object sender, EventArgs e)
{

string filePath = string.Empty;
string fileExt = string.Empty;
OpenFileDialog file = new OpenFileDialog(); //open dialog to choose file
if (file.ShowDialog() == DialogResult.OK) //if there is a file choosen by the user
{
filePath = file.FileName; //get the path of the file
fileExt = Path.GetExtension(filePath); //get the file extension
if (fileExt.CompareTo(".xls") == 0 || fileExt.CompareTo(".xlsx") == 0)
{
try
{
DataTable dtExcel = new DataTable();
dtExcel = ReadExcel(filePath, fileExt); //readexcel file
dataGridView1.Visible = true;
dtExcel.Columns.Add("Delete");
dtExcel.Columns.Add("Delay");
dtExcel.Columns.Add("Sequence");

this.dataGridView1.DataSource = dtExcel;

}
catch (Exception ex)
{
MessageBox.Show(ex.Message.ToString());
}
}
else
{
MessageBox.Show("Please choose .xls or .xlsx file only.", "Warning", MessageBoxButtons.OK, MessageBoxIcon.Error); //custom messageBox to show error
}
}
}

code was never the issue karthik issue is with the default header value which my grid is taking please check this image https://snag.gy/Y0V8CZ.jpg
i need that f1 removed and in that place filename column name to be added just that.

https://snag.gy/VrefXO.jpg here is the excel data which i am importing and just programmatically adding 3 other columns mentioned in code. while importing that F1 column header is assumed by grid and then all excel data is shown. i just need that assumption to be removed and replaced by my custom name thats all

no richard that is the connection string for importing excel below 2007 and works just fine please check https://snag.gy/Y0V8CZ.jpg for the actual problem..in this image i need that f1 removed and in that place filename column name to be added just that.

yes that was a typo thanks.have you checked that image i provided link for ?any suggestions how to remove that particular default value and replace it with my desired column name? just the name not the data

ya all the header names appearing auto except that first column which i need to change as filename or is there any alternative solution ?

name of files which i am importing that is why i need it renamed as filename instead of that F1