Exporting the excel file to gridview

protected void btnimport_Click(object sender, EventArgs e)
{
import();
}

private void import()
{
        string Filename;
        LblFileName.Text = "";
        Filename = fileupload.FileName;
        if (Filename == "")
        {
            //return "File is not selected";
        }

        LblFileName.Text = "File Name :  " + Filename.ToString();
        string path = Filename.ToString();
        GvSch.DataSource = ImportExcelXLS(path, false);
        GvSch.DataBind();
}

public static DataSet ImportExcelXLS(string FileName, bool hasHeaders)
{
string HDR = hasHeaders ? "Yes" : "No";
string strConn;
if (FileName.Substring(FileName.LastIndexOf('.')).ToLower() == ".xlsx")
strConn = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + FileName + ";Extended Properties=\"Excel 12.0;HDR=" + HDR + ";IMEX=0\"";
else
strConn = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + FileName + ";Extended Properties=\"Excel 8.0;HDR=" + HDR + ";IMEX=0\"";
 
DataSet output = new DataSet();
 
using (OleDbConnection conn = new OleDbConnection(strConn))
{
conn.Open();
 
DataTable schemaTable = conn.GetOleDbSchemaTable(
OleDbSchemaGuid.Tables, new object[] { null, null, null, "TABLE" });
 
foreach (DataRow schemaRow in schemaTable.Rows)
{
string sheet = schemaRow["TABLE_NAME"].ToString();
 
if (!sheet.EndsWith("_"))
{
try
{
OleDbCommand cmd = new OleDbCommand("SELECT * FROM [" + sheet + "]", conn);
cmd.CommandType = CommandType.Text;
 
DataTable outputTable = new DataTable(sheet);
output.Tables.Add(outputTable);
new OleDbDataAdapter(cmd).Fill(outputTable);
 
DataTable table = new DataTable();
table.Columns.Add("Date", typeof(string));
table.Columns.Add("Course", typeof(string));
table.Columns.Add("Session", typeof(string));
table.Columns.Add("Subject", typeof(string));
table.Columns.Add("Faculty", typeof(string));
 
int irow = 0;
foreach (DataRow row in outputTable.Rows)
{
if (row[1].ToString() != "Course" && row[1].ToString() != "" && row[1].ToString() != null)
{
DataRow row1 = table.NewRow();



if(row[3].ToString().Contains("+"))
                               
                                row1["Date"] = datevalue;
                                row1["Course"] = row[1].ToString();
                                row1["Session"] = "1";
                                row1["Subject"] = row[2].ToString();
                                row1["Faculty"] = row[3].ToString();

                                if (row[2].ToString().Trim() != "" && row[3].ToString().Trim() != "" && row[2].ToString().Trim() != null && row[3].ToString().Trim() != null)
                                    table.Rows.Add(row1);
                                row1 = table.NewRow();

                                if (row[5].ToString().Contains("+"))
                                    row1["Date"] = datevalue;
                                    row1["Course"] = row[1].ToString();
                                    row1["Session"] = "2";
                                    row1["Subject"] = row[2].ToString();
                                    row1["Faculty"] = row[5].ToString();
                              
  if (row[4].ToString().Trim() != "" && row[5].ToString().Trim() != "" && row[4].ToString().Trim() != null && row[5].ToString().Trim() != null)
                                    table.Rows.Add(row1);
table.Rows.Add(row1);
}
irow++;
}
output.Tables.Clear();
output.Tables.Add(table);
}
catch (Exception ex)
{
throw new Exception(ex.Message + string.Format("Sheet:{0}.File:F{1}", sheet, FileName), ex);
}
finally
{
 
}
}
}
}
return output;
}