Ref:

Using SqlBulkCopy to import Excel SpreadSheet data into SQL Server in ASP.Net using C# and VB.Net

Please refer this code.

protected void Upload(object sender, EventArgs e)
{
    //Upload and save the file
    string excelPath = Server.MapPath("~/Files/") + Path.GetFileName(FileUpload1.PostedFile.FileName);
    FileUpload1.SaveAs(excelPath);

    string conString = string.Empty;
    string extension = Path.GetExtension(FileUpload1.PostedFile.FileName);
    switch (extension)
    {
        case ".xls": //Excel 97-03
            conString = ConfigurationManager.ConnectionStrings["Excel03ConString"].ConnectionString;
            break;
        case ".xlsx": //Excel 07 or higher
            conString = ConfigurationManager.ConnectionStrings["Excel07+ConString"].ConnectionString;
            break;

    }
    conString = string.Format(conString, excelPath);
    using (OleDbConnection excel_con = new OleDbConnection(conString))
    {
        excel_con.Open();
        string sheet1 = excel_con.GetOleDbSchemaTable(OleDbSchemaGuid.Tables, null).Rows[0]["TABLE_NAME"].ToString();
        DataTable dtExcelData = new DataTable();

        //[OPTIONAL]: It is recommended as otherwise the data will be considered as String by default.
        dtExcelData.Columns.AddRange(new DataColumn[3] { new DataColumn("Id", typeof(int)),
            new DataColumn("Name", typeof(string)),
            new DataColumn("Salary",typeof(decimal)) });

        using (OleDbDataAdapter oda = new OleDbDataAdapter("SELECT * FROM [" + sheet1 + "]", excel_con))
        {
            oda.Fill(dtExcelData);
        }
        excel_con.Close();

        string consString = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
        using (SqlConnection con = new SqlConnection(consString))
        {
            using (SqlBulkCopy sqlBulkCopy = new SqlBulkCopy(con))
            {
                //Set the database table name
                sqlBulkCopy.DestinationTableName = "dbo.tblPersons1";

                //[OPTIONAL]: Map the Excel columns with that of the database table
                //sqlBulkCopy.ColumnMappings.Add("Id", "PersonId");
                //Remove the not necessary column from DataTable.
                dtExcelData.Columns.RemoveAt(0);
                sqlBulkCopy.ColumnMappings.Add("Name", "Name");
                sqlBulkCopy.ColumnMappings.Add("Salary", "Salary");
                con.Open();
                    
                sqlBulkCopy.WriteToServer(dtExcelData);
                con.Close();
            }
        }
    }
}