How to get the item before current and after current in a list with Linq / C#? -

i have list of projects , if select project give option previous , next. have add quick code example hope there better / faster way example 500 projects.

is there maybe linq option or ?

i have checked enumarator haves movenext en can't set current.

quick example:

projects dictionary

project keyvaluepair exists in dictionary

var match = false; var save = new keyvaluepair<extendedprojectlightplan, page>(); var before = new keyvaluepair<extendedprojectlightplan, page>(); var after = new keyvaluepair<extendedprojectlightplan, page>(); foreach (var p in projects) {     before = save;     save = p;      if (match)     {         after = p;         break;     }      if (p.key.id == project.key.id)     {         match = true;     }                 } 

there's nothing built linq this, write own easily... here's implementation uses tuple .net 4. return n-2 items sequence has n items - adjust if necessary.

public ienumerable<tuple<t, t, t>> withnextandprevious<t>     (this ienumerable<t> source) {     // yield "the previous two" current 1 -     // easier implement "previous , next" they're equivalent     using (ienumerator<t> iterator = source.getenumerator())     {         if (!iterator.movenext())         {             yield break;         }         t lastbutone = iterator.current;         if (!iterator.movenext())         {             yield break;         }         t previous = iterator.current;         while (iterator.movenext())         {             t current = iterator.current;             yield return tuple.create(lastbutone, previous, current);             lastbutone = previous;             previous = current;         }     }         } 

note per lukeh's answer, dictionaries unordered... above anyway.