Bug验证：.Net 4 下，貌似发现一个bug。如果是真，.Net组的员工该打屁股。

Bug 现象，点击Clear button后，操作一下UI，发现ListView的里仍然能保留第一行，太匪夷所思了。

以下是测试程序的代码：

<Window x:Class="WpfApplication37.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition />
            <RowDefinition Height="25" />
        </Grid.RowDefinitions>
        <ListView Name="WaitList">
            <ListView.View>
                <GridView>
                    <GridView.Columns>
                        <GridViewColumn Header="FirstName" DisplayMemberBinding ="{Binding Path=FirstName}" />
                        <GridViewColumn Header="LastName" DisplayMemberBinding="{Binding Path=LastName}"/>
                        <GridViewColumn Header="Age" DisplayMemberBinding="{Binding Path=Age}"/>
                    </GridView.Columns>
                </GridView>
            </ListView.View>
        </ListView>
        <StackPanel Grid.Row="1" Orientation="Horizontal" HorizontalAlignment="Center">
            <Button  Content="Load" Click="Load_Click"/>
            <Button  Content="Clear" Click="Clear_Click"/>
        </StackPanel>
    </Grid>
</Window>

------------------------------------------------------------------------------------------------------------------------------------------------------------------------

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Windows;

namespace WpfApplication37
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        List<Person> pl = new List<Person>();
        PersonComparer personComparer = new PersonComparer() { sortDirection = ListSortDirection.Ascending };

        public MainWindow()
        {
            InitializeComponent();
            WaitList.ItemsSource = pl;
        }

        private void Clear_Click(object sender, RoutedEventArgs e)
        {
            pl.Clear();
            MessageBox.Show("Cleared");
        }

        private void Load_Click(object sender, RoutedEventArgs e)
        {
            for (int i = 0; i < 40000; i++)
            {
                pl.Add(new Person(i.ToString(), "tome" + i, new Random(i).Next()));
            }

            MessageBox.Show("Loaded");
        }
    }

    public class PersonComparer : IComparer<Person>
    {
        #region IComparer<Person> Members

        public ListSortDirection sortDirection = new ListSortDirection();

        public int Compare(Person x, Person y)
        {
            return (sortDirection == ListSortDirection.Ascending ? 1 : -1) * (x.Age.CompareTo(y.Age));
        }

        #endregion
    }
}

------------------------------------------------------------------------------------------------------------------------------------------------------------------------

using System;
using System.ComponentModel;

namespace WpfApplication37
{
    public class Person : INotifyPropertyChanged
    {
        #region [ Constructor ]

        /// <summary>
        /// Initializes a new instance of the <see cref="Person"/> class.
        /// </summary>
        /// <param name="firstName">The first name.</param>
        /// <param name="lastName">The last name.</param>
        /// <param name="age">The age.</param>
        public Person(String firstName, String lastName, Int32 age)
        {
            _firstName = firstName;
            _lastName = lastName;
            _age = age;
        }

        #endregion

        #region [ Fields ]

        private String _firstName;
        private String _lastName;
        private Int32 _age;

        #endregion

        #region [ Properties ]

        /// <summary>
        /// Gets or sets the first name.
        /// </summary>
        /// <value>The first name.</value>
        public String FirstName
        {
            get { return _firstName; }
            set
            {
                if (_firstName == value) return;
                _firstName = value;
                OnPropertyChanged("FirstName");
            }

        }

        /// <summary>
        /// Gets or sets the last name.
        /// </summary>
        /// <value>The last name.</value>
        public String LastName
        {
            get { return _lastName; }
            set
            {
                if (_lastName == value) return;
                _lastName = value;
                OnPropertyChanged("LastName");
            }
        }

        /// <summary>
        /// Gets or sets the age.
        /// </summary>
        /// <value>The age.</value>
        public Int32 Age
        {
            get { return _age; }
            set
            {
                if (_age == value) return;
                _age = value;
                OnPropertyChanged("Age");
            }
        }

        #endregion

        #region [ Events ]

        public event PropertyChangedEventHandler PropertyChanged;

        #endregion

        #region [ Methods ]

        /// <summary>
        /// Called when [property changed].
        /// </summary>
        /// <param name="propertyName">Name of the property.</param>
        protected void OnPropertyChanged(String propertyName)
        {
            if (PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }

        #endregion
    }
}