Lambda expression is slower than foreach statement?

Question

I did a small experiment to test whether lamdba expression can retrieve faster results than foreach statement. but, Lambda failed

System.Diagnostics.Stopwatch st = new System.Diagnostics.Stopwatch();
        st.Start();
        List<int> lst = new List<int>();
        foreach (GridViewRow item in GridView1.Rows)
        {
            if (((CheckBox)item.FindControl("Check")).Checked)
            {
                lst.Add(Convert.ToInt32(((Label)item.FindControl("Id")).Text));
            }
        }
        st.Stop();
        Response.Write(st.Elapsed.ToString());
        Response.Write("<br/><br/><br/>");
        st.Reset();
        st.Start();
        List<int> lstRank = GridView1.Rows.OfType<GridViewRow>().Where(s => ((CheckBox)s.FindControl("Check")).Checked)
                                                                     .Select(s => Convert.ToInt32(((Label)s.FindControl("Id")).Text)).ToList();
        st.Stop();
        Response.Write(st.Elapsed.ToString());
        int i = 0;


output
00:00:00.0000249


00:00:00.0002464 

why lambda is slower than foreach. This may be a drawback of lambda expression

Answer 1

Technically your 2 approaches are not identical. There are a few differences such as the use of "OfType" which is filtering the collection before continuing. You'd be better using "Cast<GridViewRow>()" as you know each element is of type GridViewRow.

Also, do you really need the expense of the ToList() at the end of the Linq statement as your linq query is now ready to iterate over and execute rather than having to convert back to a list?