DataGrid - how to make Column sorting dynamic, to cater for when bound data changes?

I'm using a DataGrid in a VS2010 WPF C# project. I have bound the DataGrid to an ObservableCollection. When you click on a column heading it sorts the data at that point in time.

Question - How would I arrange such that the sorting in the DataGrid is dynamic, so that when data changes (within the ObservableCollection) the sorting keeps working.

Notes: Binding approach is via DataGrid

private ObservableCollection<SummaryItem> _summaryData = new ObservableCollection<SummaryItem>();
SummaryDataGrid.ItemsSource = _summaryData;

SummaryDataGrid.AutoGeneratingColumn += (s, e) =>
{
    //if (e.Column.Header.ToString() == "ProcessName")
    //    e.Column.Width = new DataGridLength(1, DataGridLengthUnitType.Star);
    e.Column.Width = new DataGridLength(1, DataGridLengthUnitType.Star);
};

public class SummaryItem : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    private string _processName;
    public string ProcessName
    {
        get { return _processName; }
        set
        {
            _processName = value;
            NotifyPropertyChanged("ProcessName");
        }
    }

    private long _total;
    public long Total
    {
        get { return _total; }
        set
        {
            _total = value;
            Noti开发者_Go百科fyPropertyChanged("Total");
        }
    }

    private long _average;
    public long Average
    {
        get { return _average; }
        set
        {
            _average = value;
            NotifyPropertyChanged("Average");
        }
    }

    private void NotifyPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs((propertyName)));
        }
    }

    public static SummaryItem ObservableCollectionSearch(ObservableCollection<SummaryItem> oc, string procName)
    {
        foreach (var summaryItem in oc)
        {
            if (summaryItem.ProcessName == procName) return summaryItem;
        }
        return null;
    }
}

You can use CollectionViewSource in code behind as well as in XAML, whose source is your datagrid's itemsource, then you can add the SortDescription/s to it. This will keep the data sorted all the time.