c# - Generic extension method is slower than non-generic extension method -

i wrote extension method lists finds index of given value (or next bigger value) in sorted list.

public static int linearsearch(this list<int> list, int startindex, int value) {     (int = startindex; < list.count; i++)         if (list[i].compareto(value) >= 0)             return i;      return -1; }  public static int linearsearch<t>(this list<t> list, int startindex, t value) t : icomparable {     (int = startindex; < list.count; i++)         if (list[i].compareto(value) >= 0)             return i;      return -1; } 

as see wrote once generic once integers. if comment out int-specific version code runs approximately slower if prove both (given work on int-lists).

how can make generic version fast non-generic one? don't want copy , paste code performance ints , longs.

the test runs 10,000,000 random queries on sorted list of 1,000 integers.

linearsearch took 9823 ms // generic linearsearch took 1553 ms // int-specific 

test-code performance-measurements

class program {     const int count = 1000;     const int runs = 10_000_000;     static list<int> list = new list<int>();     static list<int> queries = new list<int>();      static void main(string[] args)     {         measureruntime(createtestdata);         measureruntime(linearsearch);     }      private static void linearsearch()     {         foreach (int query in queries)             list.linearsearch(query);     }      private static void createtestdata()     {         random random = new random(0);         list.add(0);         (int = 0; < count; i++) list.add(list[list.count - 1] + random.next(0, 10));         (int = 0; < runs; i++) queries.add(random.next(0, list.count - 1));     }      private static void measureruntime(action action)     {         stopwatch stopwatch = new stopwatch();         stopwatch.start();         action();         stopwatch.stop();         console.writeline($"{action.getmethodinfo().name} took {stopwatch.elapsedmilliseconds} ms");     } } 

the problem used non-generic version icomparable instead of icomparable<t> caused performance-degregation. now, using icomparable<t> generic version runs fast type-specific one.

public static int linearsearch<t>(this list<t> list, int startindex, t value)      t : icomparable<t> {     (int = startindex; < list.count; i++)         if (list[i].compareto(value) >= 0)             return i;      return -1; }