hashset - nhibernate Iesi ISet fails to Remove() -

i have 2 class'es handled nhibernate : assetgroup , asset assetgroup has iset _assets collection. constructor of assetgroup say

_assets = new hashset<asset>(); 

i have operation add , remove asset in assetgroup

    public abstract class entity<tid> {     public virtual tid id { get; protected set; }      public override bool equals(object obj)     {         return equals(obj entity<tid>);     }      public static bool istransient(entity<tid> obj)     {         return obj != null && equals(obj.id, default(tid));     }      private type getunproxiedtype()     {         return gettype();     }      public virtual bool equals(entity<tid> other)     {         if (other == null)             return false;         if (referenceequals(this, other))             return true;         if (!istransient(this) && !istransient(other) && equals(id, other.id))         {             var othertype = other.getunproxiedtype();             var thistype = getunproxiedtype();             return thistype.isassignablefrom(othertype) || othertype.isassignablefrom(thistype);         }         return false;     }      public override int gethashcode()     {         if (equals(id, default(tid)))         {             return base.gethashcode();         }         else         {             return id.gethashcode();         }     } }  ///////////////////////////////////////   public class assetgroup : entity<int> {     public assetgroup()     {         this._assets = new hashedset<asset>();     }     virtual public guid securitykey {get; set;}      virtual public string name { get; set; }      private iset<asset> _assets;     virtual public iset<asset> assets     {         { return _assets; }         protected set { _assets = value; }     }      virtual public bool addasset(asset asset)     {         if (asset != null && _assets.add(asset))         {             return true;         }         return false;     }      virtual public bool removeasset(asset asset)     {         asset target = null;         foreach (var in _assets)         {             var x = a.gethashcode();             var b = a.equals(asset);             if (a.equals(asset))                 target = a;         }         if (target == null)             return false;         if (asset != null && _assets.remove(target))         {             return true;         }         return false;     }  }  ////////////////////////////////////////  public class asset : entity<int>  {     public asset()     {         securitykey = guid.newguid();     }      public virtual guid securitykey { get; set; }      virtual public int assetgroupid { { return (assetgroup != null ? assetgroup.id : 0); } }      virtual public string name { get; set; }      virtual public assetgroup assetgroup { get; set;}      virtual public void setassetgroup(assetgroup assetgroup)     {         assetgroup prevref = assetgroup;         if (prevref == assetgroup)             return;         assetgroup = assetgroup;         if (prevref != null)             prevref.assets.remove(this);         if (assetgroup != null)             assetgroup.assets.add(this);     } } 

the removeasset fails remove asset . have foreach check if asset exists in _assets . put breakpoints trace thru , foreach loop can find asset (targe) removeasset'ed . strangely enough , when ask _assets remove target. fails remove , return false. if asks _assets.contains(target) .. return false .. if foreach loop in removeasset can find target...

the 2 nhibernate mappings are

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"                assembly="mysystem.domain"                namespace="mysystem.domain" auto-import="true"> 

can me ?

are sure actual code executing? seems me if override equals , gethashcode in malfunctioning way, find asset , target assigned object _assets, remove method should never fail when called target definitly contained in set. did short test , set behaved expected.