BindingExpression路径错误:'在'对象'上找不到属性

我在WPFToolkit:DataGrid中使用数据绑定做了一些应用程序。当我运行应用程序时，我捕获了这个错误，例如:

System.Windows。数据错误:40:BindingExpression路径错误在"对象"ProcInfo"上找不到"ProcHandle"属性(HashCode = 61374531)"。BindingExpression:路径= ProcHandle;DataItem = ' ProcInfo ' (HashCode = 61374531);目标元素是'TextBlock'(Name = ");目标属性为"Text"(类型为"String")

在MainWindow.xaml:

<toolkit:DataGrid x:Name="DG1" ItemsSource="{Binding}" AutoGenerateColumns="False" Margin="0,47,0,0">
            <toolkit:DataGrid.Columns>
                <toolkit:DataGridTextColumn Header="Time/sec" Binding="{Binding KillTime}"/>
                <toolkit:DataGridTextColumn Header="Handle" Binding="{Binding ProcHandle}"/>
                <toolkit:DataGridTextColumn Header="Start Time" Binding="{Binding StartTime}"/>
                <toolkit:DataGridTextColumn Header="Status" Binding="{Binding ProcStatus}"/>
                <toolkit:DataGridTextColumn Header="Priority" Binding="{Binding ProcPriority}"/>
                <toolkit:DataGridTextColumn Header="End Time" Binding="{Binding EndTime}"/>
            </toolkit:DataGrid.Columns>
        </toolkit:DataGrid>

在MainWindow.xaml.cs

public partial class MainWindow : Window
    {
        private Process _firstProc;
        private DispatcherTimer _timerFirstProc;
        ProcessCollectionClass _procCollection = new ProcessCollectionClass();
        private int _firstProcTime;
public MainWindow()
        {
            InitializeComponent();
            DG1.DataContext = _procCollection.ProcCollection;
        }
        internal class ProcessCollectionClass : INotifyPropertyChanged
        {
            private ObservableCollection<ProcInfo> _procCollection = new ObservableCollection<ProcInfo>();
            public event PropertyChangedEventHandler PropertyChanged;
            public ObservableCollection<ProcInfo> ProcCollection
            {
                get { return _procCollection; }
                set
                {
                    _procCollection = value;
                    if (PropertyChanged != null)
                    {
                        PropertyChanged(this, new PropertyChangedEventArgs("ProcCollection"));
                    }
                }
            }
        }
        public class ProcInfo
        {
            public ProcInfo(string killTime, string procHandle, string startTime,
                            string procStatus, string procPriority)
            {
                KillTime = killTime;
                ProcHandle = procHandle;
                StartTime = startTime;
                ProcStatus = procStatus;
                ProcPriority = procPriority;
            }
            private string KillTime { get; set; }
            private string ProcHandle { get; set; }
            private string StartTime { get; set; }
            private string ProcStatus { get; set; }
            private string ProcPriority { get; set; }
        }
private void FirstProc_ButClick(object sender, RoutedEventArgs e)
        {
            _firstProcTime = Int32.Parse(FirstProcTime.Text);
            _firstProc = new Process();
            _firstProc.StartInfo.FileName = @"C:'Windows'System32'cmd.exe";
            _firstProc.StartInfo.UseShellExecute = true;
            _firstProc.Start();
            _firstProc.PriorityClass = ProcessPriorityClass.High;
            _timerFirstProc = new DispatcherTimer() { Interval = TimeSpan.FromSeconds(1) };
            _timerFirstProc.Start();
            _timerFirstProc.Tick += _timerFirstProc_Tick;
}
 void _timerFirstProc_Tick(object sender, EventArgs e)
        {
            --_firstProcTime;
            _firstProc.Refresh();
            _procCollection.ProcCollection.Add(new ProcInfo(
                                                   _firstProcTime.ToString(),
                                                   _firstProc.Handle.ToString(),
                                                   _firstProc.StartTime.ToString(),
                                                   _firstProc.Responding ? "Running" : "Not Responding",
                                                   _firstProc.PriorityClass.ToString()));
            if (_firstProcTime == 0)
            {
                _firstProc.Kill();
                _timerFirstProc.Stop();
            }
}

最后我在DataGrid中只看到空行。我做错了什么?很抱歉我的英语不好