- 如果是list中存储的是string,int等基本数据类型，直接使用Distinct方法
List<string> lst = new List<string>() {"A","B","C","A" };
var result = lst.Distinct().ToList();
2.如果存储的是类，你需要设定两个类之间重复的标准。
- 实现 IEquatable<T> 接口。
class Program
{
static void Main(string[] args)
{
List<Student> stuLst = new List<Student>() {
new Student(){ Id =1,Name = "A",Age = 10},
new Student(){ Id =2,Name = "B",Age = 12},
new Student(){ Id =3,Name = "C",Age = 13},
new Student(){ Id =1,Name = "A",Age = 11}
};
var results = stuLst.Distinct().ToList();
foreach (var result in results)
Console.WriteLine(result.Id + " " + result.Name + " " + result.Age);
Console.ReadLine();
}
}
class Student : IEquatable<Student>
{
public int Id { get; set; }
public string Name { get; set; }
public int Age { get; set; }
/// <summary>
/// Standard: If one class's Id and Name is the same as antoher class, then they are duplicate.
/// </summary>
public bool Equals(Student other)
{
if (Object.ReferenceEquals(other, null)) return false;
if (Object.ReferenceEquals(this, other)) return true;
return Id.Equals(other.Id) && Name.Equals(other.Name);
}
// If Equals() returns true for a pair of objects
// then GetHashCode() must return the same value for these objects.
public override int GetHashCode()
{
return Id.GetHashCode() ^ Name.GetHashCode();
}
}
- 实现 IEqualityComparer<T> 接口
class Program
{
static void Main(string[] args)
{
List<Student> stuLst = new List<Student>() {
new Student(){ Id =1,Name = "A",Age = 10},
new Student(){ Id =2,Name = "B",Age = 12},
new Student(){ Id =3,Name = "C",Age = 13},
new Student(){ Id =1,Name = "A",Age = 11}
};
var results = stuLst.Distinct(new StudentComparer()).ToList();
foreach (var result in results)
Console.WriteLine(result.Id + " " + result.Name + " " + result.Age);
Console.ReadLine();
}
}
class Student
{
public int Id { get; set; }
public string Name { get; set; }
public int Age { get; set; }
}
class StudentComparer : IEqualityComparer<Student>
{
/// <summary>
/// Standard: If one class's Id and Name is the same as antoher class, then they are duplicate.
/// </summary>
public bool Equals(Student x, Student y)
{
if (Object.ReferenceEquals(x, y)) return true;
if (Object.ReferenceEquals(x, null) || Object.ReferenceEquals(y, null))
return false;
return x.Id == y.Id && x.Name == y.Name;
}
public int GetHashCode(Student student)
{
if (Object.ReferenceEquals(student, null)) return 0;
return student.Id.GetHashCode() ^ student.Name.GetHashCode();
}
}
