Linq:按一列分组，但必须与其他列不同

var data = new List<Person>
{
    new Person { Name = "John", Age = 25, City = "New York" },
    new Person { Name = "Alice", Age = 30, City = "London" },
    new Person { Name = "Bob", Age = 25, City = "Paris" },
    new Person { Name = "Jane", Age = 30, City = "Berlin" }
};

var groupedData = data.GroupBy(p => new { p.Age, p.City })
                      .Select(g => new { Age = g.Key.Age, City = g.Key.City, Count = g.Count() });

foreach (var group in groupedData)
{
    Console.WriteLine($"Age: {group.Age}, City: {group.City}, Count: {group.Count}");
}