title: do something before collection changes in observablecollection in wpf
body: <p>I am not sure what i am trying to achieve is actually achievable or not.</p>
  
  <p>I have an observablecollection with me and its collectionchanged event is already been handled. What i want to do is I want to make some changes in the existing list of objects in the observablecollection just before the collectionchanged event of the observablecollection gets fired. In other words i want to do something to the existing list of objects in the observablecollection before anyone adds or removes any object from the observablecollection. Something like handling the collectionchanging event but unfortunately there is not such event in observablecollection. I hope i have been clear enough.</p>