Accessing of Rows in Silverlight DataGrid

文章摘自：http://developers.de/blogs/damir_dobric/archive/2010/05/02/accessing-of-rows-in-silverlight-datagrid.aspx

Imagine you want to enumerate (enlist) all rows (DataGridRow) of Silverlight Grid (DataGrid). By design this is not very simple tasks.
For example, you want to do something like this:

            foreach (DataGridRow rowItem in grid.Rows)
            {
                   . . .
             }

This very important and very frequent requirement is just an issue. You will notice that this is almost impossible and will start to research in internet. Good luck. So, I decided to post the code of extension class which makes this possible:

            foreach (DataGridRow rowItem in grid.GetRows())
            {
                   . . .
             }

Here is the whole code:

    /// <summary>
    /// Extends the DataGrid.
    /// </summary>
    public static class DataGridExtensions
    {
        /// <summary>
        /// Gets the list of DataGridRow objects.
        /// </summary>
        /// <param name="grid">The grid wirhrows.</param>
        /// <returns>List of rows of the grid.</returns>
        public static ICollection<DataGridRow> GetRows(this DataGrid grid)
        {
            List<DataGridRow> rows = new List<DataGridRow>();

            foreach (var rowItem in grid.ItemsSource)
            {
                // Ensures that all rows are loaded.
                grid.ScrollIntoView(rowItem, grid.Columns.Last());

                // Get the content of the cell.
                FrameworkElement el = grid.Columns.Last().GetCellContent(rowItem);

                // Retrieve the row which is parent of given element.
                DataGridRow row = DataGridRow.GetRowContainingElement(el.Parent as FrameworkElement);

                // Sometimes some rows for some reason can be null.
                if (row != null)
                    rows.Add(row);
            }

            return rows;
        }
    }

The code above shows theoretically the idea of accessing of rows. Unfortunately this will work only if the whole grid result can be placed at the current view. While calling of ScrollIntoView() grid will reuse instances of created cells and rows and replace with new bounded data over and over again. The result of so called row virtualization will be replacing of rows in the list.
To workaround this, I implemented the right extension method

public static IEnumerator<DataGridRow> GetRowsEnumerator(this DataGrid grid)
{
    return new GridRowEnumerator(grid);
}

And here is the implementation of enumerator:

  public class GridRowEnumerator : IEnumerator<DataGridRow>
    {
        private DataGrid m_Grid;

        private IEnumerator m_Enumerator;

        public GridRowEnumerator(DataGrid grid)
        {
            m_Grid = grid;

            m_Enumerator = m_Grid.ItemsSource.GetEnumerator();
        }

        #region IEnumerator<DataGridRow> Members

        public DataGridRow Current
        {
            get
            {
                var rowItem = m_Enumerator.Current;

                // Ensures that all rows are loaded.
                m_Grid.ScrollIntoView(rowItem, m_Grid.Columns.Last());

                // Get the content of the cell.
                FrameworkElement el = m_Grid.Columns.Last().GetCellContent(rowItem);

                // Retrieve the row which is parent of given element.
                //DataGridRow row = DataGridRow.GetRowContainingElement(el);
                DataGridRow row = DataGridRow.GetRowContainingElement(el.Parent as FrameworkElement);

                return row;
            }
        }

        #endregion

        #region IDisposable Members

        public void Dispose()
        {
           
        }

        #endregion

        #region IEnumerator Members

        object IEnumerator.Current
        {
            get
            {
                return this.Current;
            }
        }

        public bool MoveNext()
        {
            return m_Enumerator.MoveNext();
        }

        public void Reset()
        {
            m_Enumerator.Reset();
        }

        #endregion
    }

…

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