Extension method for UPDATE in Linq to Objects

问题:

In the following scenario, I am querying a List object and for the matching predicate I want to update some values:

var updatedList = MyList
                 .Where (c => c.listItem1 != "someValue")  
                 .Update (m => {m.someProperty = false;});

The only issue is there is no Update extension method. How to go about this?

My objective is update only those items in my list which match the condition leaving the other items intact.

回答1:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            var people = new List<Person> {
                new Person{Name="aaa", Salary=15000, isHip=false}
                ,new Person{Name="aaa", Salary=15000, isHip=false}
                ,new Person{Name="bbb", Salary=20000, isHip=false}
                ,new Person{Name="ccc", Salary=25000, isHip=false}
                ,new Person{Name="ddd", Salary=30000, isHip=false}
                ,new Person{Name="eee", Salary=35000, isHip=false}
            };


            people.Where(p => p.Salary < 25000).Update(p => p.isHip = true);

            foreach (var p in people)
            {
                Console.WriteLine("{0} - {1}", p.Name, p.isHip);
            }


        }
    }

    class Person
    {

        public string Name { get; set; }
        public double Salary { get; set; }
        public bool isHip { get; set; }
    }


    public static class LinqUpdates
    {

        public static void Update<T>(this IEnumerable<T> source, Action<T> action)
        {
            foreach (var item in source)
                action(item);
        }

    }


}

回答2:

Or you could use an extension method that comes with the .Net framework:

var updatedList = MyList
                 .Where (c => c.listItem1 != "someValue")  
                 .ForEach(m => m.someProperty = false);

回答3:

foreach(var item in MyList.Where(c => c.listItem1 != "someValue"))
{
    item.someProperty = false;
}