/// <summary>
/// build headers expressions
/// </summary>
/// <param name="columns"></param>
private void BuildColumnExpressions(IList <PivotColumn <T> > columns)
{
var EntityType = typeof(T);
var listParameterExpression = Expression.Parameter(EntityType, "obj");
PivotColumn <T> previousColumn = null;
foreach (var column in columns)
{
if (previousColumn != null)
{
previousColumn.LowerColumn = column;
column.HigherColumn = previousColumn;
}
previousColumn = column;
if (column.ValueGetter == null)
{
var propertyExpression = Expression.Property(listParameterExpression, column.PropertyName);
column.ValueGetter = Expression.Lambda <Func <T, dynamic> >(
Expression.Convert(propertyExpression, typeof(object)),
listParameterExpression).Compile();
}
if (column.TitleGetter == null)
{
column.TitleGetter = (obj) => Convert.ToString(column.ValueGetter(obj));
}
}
}
/// <summary>
/// Build Header Cell recursively
/// </summary>
/// <param name="source"></param>
/// <param name="column"></param>
/// <param name="parent"></param>
private void BuildHeaderCells(IEnumerable <T> source, PivotColumn <T> column, PivotHeaderCell <T> parent = null)
{
var list = column.Order == PivotOrder.Ascending
? source.GroupBy(column.KeySelector).OrderBy(grp => grp.Key)
: source.GroupBy(column.KeySelector).OrderByDescending(grp => grp.Key);
foreach (var group in list)
{
var cell = new PivotHeaderCell <T>(group.First(), column);
column.Cells.Add(cell);
if (parent != null)
{
parent.__Children.Add(cell);
}
cell.Parent = parent;
if (column.LowerColumn != null)
{
BuildHeaderCells(group, column.LowerColumn, cell);
}
}
}
internal PivotHeaderCell(T leadObjet, PivotColumn <T> column)
{
LeadObject = leadObjet;
Column = column;
}