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  • List<>中Find的用法

    I've been looking for help on how to find objects in Generics with List.Find() method .... and ... take a look what I have found.
    In the follow example, I created a simple class:

    public class Person
    {
           private int _id;
           private string _name;

           public int ID {  get{ return _id;} set{ _id = value;}}
           public int Name {  get{ return _name;} set{ _name= value;}}

           public Person(int id, string name)
           {
                 _id = id;
                 _name = name;
           }
    }

    In the example, there's a simple class with two private attributes. Now we're going to create a typed List of this object and take advantage of the Find() method

    public void CreateAndSearchList()
    {
          //create and fill the collection
          List<Person> myList = new List<Person>();
          myList.Add(new Person(1, "AndreySanches"));
          myList.Add(new Person(2, "AlexandreTarifa"));
          myList.Add(new Person(3, "EmersonFacunte"));

         //find a specific object
         Person myLocatedObject = myList.Find(delegate(Person p) {return p.ID == 1; });
    }

    备注:在list和array集合中搜索元素经常使用该方法,主要技术是泛型委托

    list用法注意:如果增加一个对象,必须重新new一个对象,看下面的例子:

    person p=new pewson();
    for(int i=0;i<5;i++)
    {
    p.ID=i;
    p.Name="xxxx";
    list.add(p);
    }

    for(int i=0;i<5;i++)
    {
    person p=new person();
    p.ID=i;
    p.Name="xxxx";
    list.add(p);
    }

    上 面有区别吗?在输出list的值是有区别了,第一个list里面存放的都是一样的,结果和最后一个一样,都是同一个人对象,第二个list达到预期的效 果,存储不同的人对象。这是为什么?原因很简单,一个list对象中存储的都是对一个共有的对象进行引用,所以以最后改变的值为准。

    对象的排序:本文主要阐述对存储datatable的list进行按TableName排序

    1、新建一个sort类

    public class SceneSort:IComparer<DataTable>
        {
           public int Compare(DataTable obj1, DataTable obj2)
           {
               int tableNameLength1;
               int tableNameLength2;
               if (obj1 == null)
               {
                   if (obj2 == null)
                       return 0;
                   else
                       return -1;
               }
               else
               {
                   if (obj2 == null)
                       return 1;
                   else
                   {
                       tableNameLength1=obj1.TableName.Length;
                       tableNameLength2=obj2.TableName.Length;
                       if (Convert.ToInt32(obj1.TableName.Substring(2,tableNameLength1-2))>Convert.ToInt32(obj2.TableName.Substring(2,tableNameLength2-2)))
                           return 1;                            //大于返回1
                       else if (Convert.ToInt32(obj1.TableName.Substring(2,tableNameLength1-2))<Convert.ToInt32(obj2.TableName.Substring(2,tableNameLength2-2)))
                           return -1;                           //小于返回-1
                       else
                           return 0;                            //相等返回0
                   }
               }

           }
    2 排序:
    List<DataTable> ldt = new List<DataTable>();
    SceneSort ss=new SceneSort ();
    tablelist.sort(ss);即可对list进行排序;

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  • 原文地址:https://www.cnblogs.com/zhangchenliang/p/2050353.html
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