c# - Why my second ObservableCollection is getting update? -

i have two observablecollections filled items (that items observablecollecions filled other types of object) of same type.

_treeviewbase - first observablecollection 'base' data.

_tvdata - second observablecollection should store 'needed' items, have treeview itemsource binded tvdata.

function fillaliastreeview used fill _treeviewbase data not paste code here.

when @ begining of program assign _treeviewbase _tvdata in loadsidebar() function ok. both of observablecollection storing data.

but when search ( , tvdata modified in searchbox_textchanged() ) it's seems _treeviewbase modified.

how possible? did made major mistake in code?

my class ( full code ) :

public partial class sidebar : page, inotifypropertychanged {     private observablecollection<connectionmodel> _treeviewbase;     private observablecollection<connectionmodel> _tvdata ;        public sidebar()     {         treeviewbase = new observablecollection<connectionmodel>( connectionutilities.loadobservableconnections() ) ;         tvdata       = new observablecollection<connectionmodel>();          initializecomponent();           datacontext = this;          var loadsidebar = task.factory.startnew( async () => { await loadsidebar();   } );         loadsidebar.wait();          onpropertychanged("tvdata");     }       public async task loadsidebar()     {         // function used fill _treeviewbase           await fillaliastreeview();          tvdata = treeviewbase;         onpropertychanged("tvdata");      }       private async void searchbox_textchanged(object sender, textchangedeventargs e)     {         string newsearchtext = searchbox.text;          if ( (newsearchtext == "" || newsearchtext == "search..." || newsearchtext.length < 3  )  )          {              tvdata.clear();             tvdata = null;              messagebox.show( (tvdata == null).tostring() + " " + treeviewbase.count.tostring());               tvdata = new observablecollection<connectionmodel>( treeviewbase );              aliastree.itemssource = tvdata ;              aliastree.updatelayout();              return;         }          searchtext = searchbox.text;           if (tvdata != null)         {             await dispatcher.invokeasync(             () =>             {                 foreach (connectionmodel cm in tvdata.tolist<connectionmodel>())                 {                     foreach (schemamodel sm in cm.schemas.tolist<schemamodel>())                     {                         foreach (schemacollection sc in sm.schema_collections.tolist<schemacollection>())                         {                             try                             {                                 observablecollection<tablemodel> octm = (observablecollection<tablemodel>)sc.collection;                                  (int = 0; < octm.count; i++)                                 {                                     if (!(sc.collection observablecollection<tablemodel>)[i].table_name.contains(searchtext))                                     {                                         (sc.collection observablecollection<tablemodel>).removeat(i);                                         = - 1;                                     }                                     dispatcher.invokeasync( () => onpropertychanged("tables") ) ;                                 }                                 dispatcher.invokeasync(() => onpropertychanged("collection") );                             }                             catch (exception exc) { }                         }                         dispatcher.invokeasync(() => onpropertychanged("schemas") );                     }                     dispatcher.invokeasync(() => onpropertychanged("tvdata"));                 }                 dispatcher.invokeasync(() => onpropertychanged("tvdata"));             });              await dispatcher.invokeasync(() => expandall(aliastree));         }     }       private void expandall( itemscontrol root )     {         if ( root != null )         {             foreach (var subitem in root.items)             {                 if (subitem != null)                 {                     expandall( (treeviewitem)root.itemcontainergenerator.containerfromitem(subitem) );                     try                     {                         if (((treeviewitem)root.itemcontainergenerator.containerfromitem(subitem) treeviewitem) != null )                             ((treeviewitem)root.itemcontainergenerator.containerfromitem(subitem) treeviewitem).isexpanded = true;                     }                     catch (exception exc) { };                 }             }              aliastree.updatelayout();         }     } 

thank suggestions.

in constructor, set tvdata , treeviewbase 2 different instances of observablecollection<>. line:

tvdata = treeviewbase; 

makes them refer same instance. old tvdata observable collection discarded, , both of variables refer same observable collection.

this how reference types work.