C#/MVVM: Enable/Disable Buttons based on another control's property -

say have tab control displays data of various types, eg editortabviewmodel, previewtabviewmodel both inheriting tabviewmodel. implementation similar tutorial on msdn

i want enable buttons depending on active tab, whether editortabviewmodel or previewtabviewmodel. how can achieve this?

update

public icommand editorcommand {         {         if (_editorcommand == null) {             _editorcommand = new relaycommand(() =>             {                 messagebox.show("editor");             }, () =>             {                 var enabled = true;                 var viewsource = collectionviewsource.getdefaultview(tabs);                 viewsource.currentchanged += (o, e) =>                 {                     if (viewsource.currentitem editortabviewmodel)                     {                         enabled = false;                     }                 };                 return enabled;             });         }         return _editorcommand;     } } 

update 2

public icommand previewcommand {         {         if (_previewcommand == null) {             _previewcommand = new relaycommand(() =>             {                 messagebox.show("preview");             }, () =>             {                 var viewsource = collectionviewsource.getdefaultview(tabs);                 var enabled = viewsource.currentitem editortabviewmodel;                 viewsource.currentchanged += (o, e) =>                 {                     commandmanager.invalidaterequerysuggested();                 };                 return enabled;             });         }         return _previewcommand;     } } 

i suggest create icommand implementation constructs on icollectionview contains 2 tab controls. command can react currentchanged event collection view determine whether or not should enabled, , raise canexecutechanged event indicate change.

class mycommand : icommand {     private bool _isenabled = true;      public mycommand(mytoplevelviewmodel viewmodel)     {         var viewsource = collectionviewsource.getdefaultview(viewmodel.tabs);         viewsource.currentchanged += (o,e) =>             {                 _isenabled = (viewsource.currentitem editortabviewmodel); //or want decide                  if (this.canexecutechanged != null)                       this.canexecutechanged(this, eventargs.empty);              };     }      public void execute(object parameter) { /*...*/ }      public bool canexecute(object parameter) { return _isenabled; }      public event eventhandler canexecutechanged; } 

note: need set issyncronizedwithcurrentitem property on tab control:

<tabcontrol issynchronizedwithcurrentitem="true" />