<TextBox x:Name="tbSeach" Height="25" Width="60" HorizontalAlignment="Center" VerticalAlignment="Top"  TextChanged="tbSeach_TextChanged"/>

               private void tbSeach_TextChanged(object sender, TextChangedEventArgs e)
        {
            _seachfooList = new List<FooViewModel>();
            foreach (FooViewModel model in treeGoods.Items)
            {
                foreach (FooViewModel foo in findNode(model, tbSeach.Text.Trim()))
                {
                    foo.IsChecked = true;
                };
            }
        }

        //模糊查询算法
        private List<FooViewModel> findNode(FooViewModel tnParent, string strValue)
        {
            if (tnParent == null) return null;
            if (tnParent.Name.IndexOf(strValue) > -1 && !string.IsNullOrEmpty(strValue))
            {
                _seachfooList.Add(tnParent);
            }
            foreach (FooViewModel foo in tnParent.Children)
            {
                foo.IsChecked = false;
                findNode(foo, strValue);
            }
            return _seachfooList;
        }