How to use order by and group by in C#?-C#.Net Tutorial-php.cn

C#中如何使用order by、group by？

Order by is used to sort the arrays in the ascending or in the descending order

GroupBy operator belong to Grouping Operators category. This operator takes a flat sequence of items, organize that sequence into groups (IGrouping ) based on a specific key and return groups of sequence

Example

class ElectronicGoods { public int Id { get; set; } public string Name { get; set; } public string Category { get; set; } public static List GetElectronicItems() { return new List() { new ElectronicGoods { Id = 1, Name = "Mobile", Category = "Phone"}, new ElectronicGoods { Id = 2, Name = "LandLine", Category = "Phone"}, new ElectronicGoods { Id = 3, Name = "Television", Category = "TV"}, new ElectronicGoods { Id = 4, Name = "Grinder", Category = "Food"}, new ElectronicGoods { Id = 5, Name = "Mixer", Category = "Food"}, }; } } class Program { static void Main() { //Group by var res=ElectronicGoods.GetElectronicItems().GroupBy(x => x.Category).Select(x => new { Key = x.Key, electronicGoods = x.OrderBy(c => c.Name) }); foreach (var group in res) { Console.WriteLine("{0} - {1}", group.Key, group.electronicGoods.Count()); Console.WriteLine("----------"); foreach (var electronicGoods in group.electronicGoods) { Console.WriteLine(electronicGoods.Name + "\t" + electronicGoods.Category); } Console.WriteLine(); Console.WriteLine(); } Console.ReadKey(); } }

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Output

Phone - 2 ---------- LandLine Phone Mobile Phone TV - 1 ---------- Television TV Food - 2 ---------- Grinder Food Mixer Food

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Order By

的翻译为：

按顺序排列

class ElectronicGoods { public int Id { get; set; } public string Name { get; set; } public string Category { get; set; } public static List GetElectronicItems() { return new List() { new ElectronicGoods { Id = 1, Name = "Mobile", Category = "Phone"}, new ElectronicGoods { Id = 2, Name = "LandLine", Category = "Phone"}, new ElectronicGoods { Id = 3, Name = "Television", Category = "TV"}, new ElectronicGoods { Id = 4, Name = "Grinder", Category = "Food"}, new ElectronicGoods { Id = 5, Name = "Mixer", Category = "Food"}, }; } } class Program { static void Main() { //Order by var res = ElectronicGoods.GetElectronicItems().OrderBy(x => x.Category); foreach (var items in res) { Console.WriteLine(items.Name + "\t" + items.Category); } Console.ReadKey(); } }

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Output

Grinder Food Mixer Food Mobile Phone LandLine Phone Television TV

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