我要评论一、示例代码
using system;
using system.collections.generic;
using system.linq;
public class program
{
public static void main()
{
// 创建一些示例实体对象
var people = new list<person>
{
new person { name = "alice", age = 30, city = "new york" },
new person { name = "bob", age = 25, city = "los angeles" },
new person { name = "alice", age = 30, city = "new york" },//重复的
new person { name = "charlie", age = 35, city = "chicago" },
new person { name = "alice", age = 28, city = "san francisco" }
};
// 1. 单字段去重
var uniquenamefields = people.distinctby(p =>p.name).tolist();
console.writeline("指定字段（name）去重结果,重复则保留第一条:");
foreach (var person in uniquenamefields)
{
console.writeline($"name: {person.name}, age: {person.age}, city: {person.city}");
}
// 2. 多字段去重
var uniquenameagefields = people.distinctby(p => new { p.name, p.age }).tolist();
console.writeline("\n指定字段（name, age）去重结果,重复则保留第一条:");
foreach (var person in uniquenameagefields)
{
console.writeline($"name: {person.name}, age: {person.age}, city: {person.city}");
}
//3.全字段去重
// 通过 groupby 按 name 和 age 字段去重
var uniquepeople = people.distinctby(p => new { p.name, p.age, p.city }).tolist();
console.writeline("\n全字段去重:");
foreach (var person in uniquepeople)
{
console.writeline($"name: {person.name}, age: {person.age}, city: {person.city}");
}
}
}
public class person
{
public string name { get; set; }
public int age { get; set; }
public string city { get; set; }
}二、示例输出
指定字段（name）去重结果,重复则保留第一条:
name: alice, age: 30, city: new york
name: bob, age: 25, city: los angeles
name: charlie, age: 35, city: chicago
指定字段（name, age）去重结果,重复则保留第一条:
name: alice, age: 30, city: new york
name: bob, age: 25, city: los angeles
name: charlie, age: 35, city: chicago
name: alice, age: 28, city: san francisco
全字段去重:
name: alice, age: 30, city: new york
name: bob, age: 25, city: los angeles
name: charlie, age: 35, city: chicago
name: alice, age: 28, city: san francisco
三、注意雷点
以下代码不能完成全字段去重，因为people是引用类型，distinct() 一般用于list<string>,list<int>这些值类型去重，而不涉及引用类型的字段比较。
people.distinct().tolist()
若需要全字段去重：1.使用dinstinctby语法，加上所有字段。2.使用标题四的封装方法（反射实现全字段去重）。
四、全字段去重封装方法
1.封装
/// <summary>
/// 通用的全字段去重方法
/// </summary>
/// <returns></returns>
public static ienumerable<t> distinctbyallfields<t>(ienumerable<t> items)
{
// 获取 t 类型的所有字段值
var properties = typeof(t).getproperties(bindingflags.public | bindingflags.instance);
return items
.groupby(item => string.join(",", properties.select(p => p.getvalue(item)))) // 按所有字段值连接生成唯一标识符
.select(group => group.first()); // 取每组的第一个元素
}2.示例
using system;
using system.collections.generic;
using system.linq;
using system.reflection;
public class program
{
public static void main()
{
// 创建一些示例实体对象
var people = new list<person>
{
new person { name = "alice", age = 30, city = "new york" },
new person { name = "bob", age = 25, city = "los angeles" },
new person { name = "alice", age = 30, city = "new york" },
new person { name = "charlie", age = 35, city = "chicago" },
new person { name = "alice", age = 28, city = "san francisco" }
};
// 调用封装的去重方法
var uniquepeople = distinctbyallfields(people).tolist();
console.writeline("根据所有字段去重的结果:");
foreach (var person in uniquepeople)
{
console.writeline($"name: {person.name}, age: {person.age}, city: {person.city}");
}
}
/// <summary>
/// 通用的全字段去重方法
/// </summary>
/// <returns></returns>
public static ienumerable<t> distinctbyallfields<t>(ienumerable<t> items)
{
// 获取 t 类型的所有字段值
var properties = typeof(t).getproperties(bindingflags.public | bindingflags.instance);
return items
.groupby(item => string.join(",", properties.select(p => p.getvalue(item)))) // 按所有字段值连接生成唯一标识符
.select(group => group.first()); // 取每组的第一个元素
}
}
public class person
{
public string name { get; set; }
public int age { get; set; }
public string city { get; set; }
}以上就是c#使用linq实现简单去重处理的详细内容，更多关于c# linq去重的资料请关注代码网其它相关文章！
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