c# - Foreach substitute in Linq -

i have query want substitue foreach linq because foreach slow how can write codein 1 query code:

    ret = new list<reportdata>();     foreach (var item in number)     {         string = item.substring(0, 11);         string b = item.substring(14, 2);         string c = item.substring(19, 11);         string d = item.substring(33);         ret1 = (from in report                 a.a == && a.b == b && a.c == c && a.d == d && filter.type.contains(a.y)                  select new reportdata                 {                     x = a.x,                     y = a.y,                 });        if (ret1 != null && ret1.tolist().count > 0)           {              ret.addrange(ret1);           }        } 

as mentioned in comments, linq not make foreach faster; if have iterate entire collection, foreach faster linq.

there no need check null or if results exists in inner linq statement; add range since linq query return enumerable.empty<reportdata> if nothing returned query.

if (ret1 != null && ret1.tolist().count > 0) {   ret.addrange(ret1); }    // becomes ret.addrange(ret1); 

assumming number collection of string, make sure there no duplicates:

foreach (string item in number.distinct()) 

if number large list, thousands of items or more, consider using parallel.foreach.