Converting LINQ query to Dynamic Linq

I have a function that looks like this:

public void GetAvailableResourcesByLocationChart(List<DateTime> dates, List<ChartResourceModel> data)
{
    var totals = (from r in data
                  group new { Dates = r.Dates } by r.Location into g
                  select new
                  {
                      Location = g.Key,
                      Dates = dates.Select(d => new
                      {
                          Date = d,
                          Available = g.SelectMany(x => x.Dates.Where(y => y.Date == d)).Count(x => x.Available)
                      })
                      .OrderBy(x => x.Date)
                      .ToList()
                  })
                 .OrderBy(x => x.Location)
                 .ToList();
 }

This example groups the data based on Location. But I want to be able to pass in a string that specifies what it should group on. I was thinking DynamicLinq would be the right way to go about this but I'm having trouble reproducing it.

I started off doing this, but am getting stuck reproducing the SelectMany inside the select:

public void GetAvailableResourcesByLocationChart(List<DateTime> dates, List<ChartResourceModel> data, string grouping)
{
    var totals = data.GroupBy(grouping, "it").Select("new (it.Key as Group, it as Dates)").Cast<dynamic>();
}

Any ideas on what I need to do next?