Collection ViewSource to filter listbox by typing in textbox

Question

I have a listbox in WPF where users firstname and lastname are listed. I have a textbox, and I am trying to filter as I type by the names. Here is what I am trying: (Nothing is being filtered when I am typing in the textbox)

Here is my VM

        #region Members

        private CollectionViewSource usercvs = new CollectionViewSource();
        private string searchString;

        #endregion

        #region Properties

        public string SearchFilter
        {
            get
            {
                return this.searchString;
            }

            set
            {
                if (!string.IsNullOrEmpty(this.searchString))
                    AddFilter();

                usercvs.View.Refresh();    
                this.searchString = value;
            }
        }

        #endregion

        #region Methods

        private void AddFilter()
        {
            usercvs.Filter -= new FilterEventHandler(Filter);
            usercvs.Filter += new FilterEventHandler(Filter);

        }

        private void Filter(object sender, FilterEventArgs e)
        {
            // see Notes on Filter Methods:
            var src = e.Item as User;
            if (src == null)
                e.Accepted = false;
            else if (src.LastName != null && !src.LastName.Contains(SearchFilter))
                e.Accepted = false;
        }

        #endregion
    }
}

Answer 1

Add an additional property to your ViewModel that exposes the CollectionViewSource and bind your ListBox to that property.

public CollectionViewSource FilteredUsers{
  get {
    return usercvs.View;
  }
}

The ObservableCollection is not changed when you apply any filters to the CollectionViewSource, so that you will always see all items. The Filter gets applied to the CollectionViewSource and the filtered result can be accessed by the property View of the class.