class DataGridSettings
    {
        public DataGrid Grid { get; set; }        

        public DataGridState Value
        {
            get
            {
                int columnIndex = 0;
                return new DataGridState()
                {
                    Columns = Grid
                        .Columns
                        .Where(v => v.DisplayIndex >= 0)
                        .Select(v =>
                        {
                            var result = new DataGridColumnState()
                            {
                                Index = columnIndex,
                                DisplayIndex = v.DisplayIndex,
                                Visibility = v.Visibility,
                                Width = v.ActualWidth
                            };
                            columnIndex++;
                            return result;
                        })
                        .ToArray()
                };
            }
            set
            {
                if (value == null || value.Columns.Length != Grid.Columns.Count)
                    return;

                foreach (var columnState in value.Columns.OrderBy(v => v.DisplayIndex))
                {
                    var column = Grid.Columns[columnState.Index];

                    if (columnState.DisplayIndex >= 0)
                        column.DisplayIndex = columnState.DisplayIndex;

                    column.Visibility = columnState.Visibility;
                    column.Width = columnState.Width;
                }
            }
        }
    }

    public class DataGridState
    {
        public DataGridColumnState[] Columns { get; set; }
    }

    public class DataGridColumnState
    {
        public int Index { get; set; }
        public int DisplayIndex { get; set; }
        public Visibility Visibility { get; set; }
        public double Width { get; set; }
    }