page collection view not updating datagtidgrid ui after updating an item in obserbationcolletion

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C#

Silverlight

Hi,
I am binding a datagrid from pagecollectionview with grouping. Its working fine, but when I am updating a record in datagrid then datagrid UI is not getting refreshed.
But when I am checking, the updated record exist in consoleCollection.
Please help.

if (grdConsole.ItemsSource == null)
{
      ConsoleCollection = e.Result.Response;
      grdConsole.ItemsSource = GetGroupedCollection(ConsoleCollection, CurrentGroupByColumn);              
}
else
{
      foreach (Task data in e.Result.Response.OrderBy(item =>item.TaskID))
      {
            var existingData = (from con in this.ConsoleCollection
                                where con.TaskID == data.TaskID
                                select con).FirstOrDefault();
            if (existingData != null)
            {
                  this.ConsoleCollection.Remove(existingData);
            }

            this.ConsoleCollection.Add(data);
       }

}