c# - Difficulty with LINQ -

i'm having difficulty ienumerable , linq. perhaps don't understand fully.

i have data source of fake files ("plumfile"), , filters. each filter has fits(plumfile) determines if argument fits filter. each filter has enum indicating if it's "and", "or", or "not".

here how i'm trying combine filters query:

    public observablecollection<plumfile> foundfiles     {                 {             observablecollection<plumfile> searchresults = new observablecollection<plumfile>();              // data source             ienumerable<plumfile> query = plumdata.getfiles();              foreach (filterconstraint filter in filters)             {                 // debugging                 ilist<plumfile> oldquery = query.tolist();                  switch (filter.querycombiningrule)                 {                     case filterconstraint.queryrule.and:                         query = query.where(file => filter.fits(file));                         break;                     case filterconstraint.queryrule.or:                         query = query.concat(plumdata.getfiles().where(file => filter.fits(file)));                         break;                      // how want 'not'?                     case filterconstraint.queryrule.not:                         query = query.where(file => !filter.fits(file));                         break;                 }                  // debugging                 ilist<plumfile> currquery = query.tolist();              }              query = query.distinct();              foreach (plumfile file in query)             {                 searchresults.add(file);             }              return searchresults;         }     } 

i'm not sure i'm doing wrong. queries, works fine. others, fails.

if have single "and" filter, works fine. add "not" filter shouldn't filter out selected, removed. why this?

(i'm doing silverlight 4 app, don't think matters.)

update: 1 example of filter constraint:

public class namefilterconstraint : filterconstraint {     public string name { get; set; }      public override bool fits(plumfile plumfile)     {         return plumfile.name.contains(name);     }      public override string description     {                 {             return tostring();         }     }      public override string tostring()     {         return string.format("name contains '{0}'", name);     } } 

update 2: here non-linq version doesn't have bugs mentioned earlier:

public observablecollection<plumfile> foundfiles         {                         {                 observablecollection<plumfile> searchresults = new observablecollection<plumfile>(plumdata.getfiles().tolist());                  foreach (filterconstraint filter in filters)                 {                     switch (filter.querycombiningrule)                     {                         case filterconstraint.queryrule.and:                             foreach (plumfile file in searchresults.tolist())                             {                                 if (! filter.fits(file))                                 {                                     searchresults.remove(file);                                 }                             }                             break;                          case filterconstraint.queryrule.or:                             foreach (plumfile file in plumdata.getfiles())                             {                                 if (filter.fits(file))                                 {                                     searchresults.add(file);                                 }                             }                             break;                          case filterconstraint.queryrule.not:                             foreach (plumfile file in searchresults.tolist())                             {                                 if (filter.fits(file))                                 {                                     searchresults.remove(file);                                 }                             }                             break;                     }                 }                  return new observablecollection<plumfile>(searchresults.distinct());             }         } 

so, guess problem solved, although i'm still curious doing wrong linq. perhaps intentions (made clear in last example) not translated linq properly?

just guess here, wonder if capture/closure issue. try this:

    public observablecollection<plumfile> foundfiles     {                 {             observablecollection<plumfile> searchresults = new observablecollection<plumfile>();              // data source             ienumerable<plumfile> query = plumdata.getfiles();              foreach (filterconstraint filter in filters)             {                 var localfilter = filter;                 // debugging                 ilist<plumfile> oldquery = query.tolist();                  switch (filter.querycombiningrule)                 {                     case filterconstraint.queryrule.and:                         query = query.where(file => filter.fits(file));                         break;                     case filterconstraint.queryrule.or:                         query = query.concat(plumdata.getfiles().where(file => localfilter.fits(file)));                         break;                      // how want 'not'?                     case filterconstraint.queryrule.not:                         query = query.where(file => !localfilter.fits(file));                         break;                 }                  // debugging                 ilist<plumfile> currquery = query.tolist();              }              query = query.distinct();              foreach (plumfile file in query)             {                 searchresults.add(file);             }              return searchresults;         }     }