如何改善数据透视表功能

Question

我正在使用以下功能转换为行到列，但是我只能在1秒内旋转4行。这对我的应用来说太慢了

    public static DataTable ToPivotTable<T, TColumn, TRow, TData>(
this IEnumerable<T> source,
Func<T, TColumn> columnSelector,
Expression<Func<T, TRow>> rowSelector,
Func<IEnumerable<T>, TData> dataSelector)
    {
        DataTable table = new DataTable();
        var rowName = ((MemberExpression)rowSelector.Body).Member.Name;
        table.Columns.Add(new DataColumn(rowName.ToString(), typeof(DateTime)));
        var columns = source.Select(columnSelector).Distinct();

        foreach (var column in columns)
            table.Columns.Add(new DataColumn(column.ToString(), typeof(double)));

        var rows = source.GroupBy(rowSelector.Compile())
                         .Select(rowGroup => new
                         {
                             Key = rowGroup.Key,
                             Values = columns.GroupJoin(
                                 rowGroup,
                                 c => c,
                                 r => columnSelector(r),
                                 (c, columnGroup) => dataSelector(columnGroup))
                         });

        foreach (var row in rows)
        {
            var dataRow = table.NewRow();
            var items = row.Values.Cast<object>().ToList();
            items.Insert(0, row.Key);
            dataRow.ItemArray = items.ToArray();
            table.Rows.Add(dataRow);
        }

        return table;
    }

我意识到接下来的每一行需要250毫秒才能完成。这是主要问题。

 var items = row.Values.Cast<object>().ToList();

如何提高该行的效果？