C# List 、 HashSet类去重

 

一、HashSet去重

1、对简单类型的去重

HashSet<int> ints = new HashSet<int>() { 1,2,3,4,5,6,7,8,9,8,7,6,5,4,3,2,1};

foreach (var item in ints)
{
    Console.WriteLine(item);
}

 

 2、对象集合去重

class person
{
    public string name { get; set; }
    public string   sex { get; set; }
    public byte age { get; set; }

    public override bool Equals(object? obj)
    {
        var o=obj as person;
        return this.name == o.name;
    }
    public override int GetHashCode()
    {
        return this.name.GetHashCode();
    }
    public override string ToString()
    {
        return $"{name}:{age}:{sex}";
    }
}

HashSet<person> p = new HashSet<person>();
p.Add(new person { name = "张三", age = 11, sex = "男" });
p.Add(new person { name = "李四", age = 11, sex = "男" });
p.Add(new person { name = "王五", age = 11, sex = "女" });
p.Add(new person { name = "张三", age = 11, sex = "男" });
p.Add(new person { name = "王五", age = 11, sex = "男" });
foreach (var item in p)
{
    Console.WriteLine(item);
}

 

二、List去重

 

List<person> p = new List<person>();
p.Add(new person { name = "张三", age = 11, sex = "男" });
p.Add(new person { name = "李四", age = 11, sex = "男" });
p.Add(new person { name = "王五", age = 11, sex = "女" });
p.Add(new person { name = "张三", age = 11, sex = "男" });
p.Add(new person { name = "王五", age = 11, sex = "男" });
foreach (var item in p.DistinctBy(x=>x.name))
{
    Console.WriteLine(item);
}