今日在Code Review 同事的Code 時候發現了一個有趣的寫法
他想做的是 Return 一個Distinct 左既 List Of Object
好直接既想法是使用 Distinct
List.Distinct();
之後發現Distinct 是不能 Distinct Object的
同事的寫法是用了 List 加 GroupBy 和Select First()
List.GrounBy(x=> x.key).Select(x => x.First())
之後發現.. 原來我們可以使用 GroupBy 加 First 來做到 Distinct Object的效果
以下是我的 Code Sample
void Main()
{
var list = new List<Example>();
list.Add(new Example() {Id=1, Name="Example 1", Comment="Comment 1" });
list.Add(new Example() {Id=1, Name="Example 1", Comment="Comment 1" });
list.Add(new Example() {Id=1, Name="ExamplE 1", Comment="Comment 2" });
list.Add(new Example() {Id=2, Name="Example 2", Comment="Comment 3" });
list.Add(new Example() { Id = 2, Name = "example 2", Comment = "Comment 3" });
list.Add(new Example() { Id = 3, Name = "Example 3", Comment = "Comment 3" });
list.Add(new Example() { Id = 4, Name = "Example 4", Comment = "Comment 3" });
list.Add(new Example() { Id = 5, Name = "Example 5", Comment = "Comment 3" });
Console.WriteLine("Use List.Distinct()");
list.Distinct().Dump();
Console.WriteLine("Use Group By Fields");
list.GroupBy(x => new {x.Id, Name=x.Name}).Select(x =>x.First()).Dump();
Console.WriteLine("Use Group By and make it ignore case");
list.GroupBy(x => new {x.Id, Name=x.Name.ToLower()}).Select(x =>x.First()).Dump();
}
public class Example
{
public int Id { get; set; }
public string Name { get; set; }
public string Comment {get;set;}
}
Output:
