c#入门经典 part 6

var results = 
    from n in names
    where n.StartsWith("S")
    orderby n descending 
    select n // select new(n, ...)
    ;

var results = names.OrderBy(n => n).Where(n => n.StartsWith("S"));
var results = names.OrderByDescending(n => n.Substring(n.Length - 1)).Where(n => n.StartsWith("S")).select(n => new(n, ...)).Distinct();

results.Count();
results.Max();
results.Min();
results.Average();
results.Sum(n => (long) n);

bool res = customers.Any(c => c.Name == "Tom");
bool res = customers.All(c => c.Name == "Tom");

orderby c.Name, c.Age

var res = customers.OrderBy(c => c.Name).ThenBy(c => c.Age)...;

var res =
    from c in customers
    group c by c.Region into cg
    select new {TotalSales = cg.Sum(c => c.Sales), Region = cg.Key}
    ;

var res =
    from c in customers
    join o in orders on c.ID equals o.ID
    ;