Statistik GetStatistik()
{
 return new Statistik()
 {
  Min = DataContext.Messungen.Min(m => m.Wert),
  Max = DataContext.Messungen.Max(m => m.Wert),
  Avg = DataContext.Messungen.Average(m => m.Wert),
  Cnt = DataContext.Messungen.Count(),
 };
}

var stats = dc.ExecuteQuery<double>(
     "SELECT MAX(Wert), MIN(Wert), AVG(Wert) " +
     "FROM Messungen");

var stats = from m in messungen
            group m by 1 into grp
            select new
            {
                        Max = grp.Max(g => g),
   Min = grp.Min(g => g),
   Avg = grp.Average(g => g)
            };