The following lines of code will do the trick:
private void Form1_Load(object sender, EventArgs e)
{
DataTable dtExcel = GetDataFromExcel();
System.IO.File.Delete("C:\\my\\Book1.xls");
}
public DataTable GetDataFromExcel()
{
DataTable dt = new DataTable();
con.ConnectionString = connectionString;
cmd.Connection = con;
OleDbDataAdapter dap = new OleDbDataAdapter();
dap.SelectCommand = cmd;
dap.Fill(dt);
return dt;
}