List<>中Find的用法小結(jié)

2020-01-24 02:51:11

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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:

復(fù)制代碼代碼如下:

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

復(fù)制代碼代碼如下:

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; });
}

備注：在list和array集合中搜索元素經(jīng)常使用該方法，主要技術(shù)是泛型委托

list用法注意：如果增加一個(gè)對(duì)象，必須重新new一個(gè)對(duì)象，看下面的例子：

復(fù)制代碼代碼如下:

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);
}

上面有區(qū)別嗎？在輸出list的值是有區(qū)別了，第一個(gè)list里面存放的都是一樣的，結(jié)果和最后一個(gè)一樣，都是同一個(gè)人對(duì)象，第二個(gè)list達(dá)到預(yù)期的效果，存儲(chǔ)不同的人對(duì)象。這是為什么？原因很簡(jiǎn)單，一個(gè)list對(duì)象中存儲(chǔ)的都是對(duì)一個(gè)共有的對(duì)象進(jìn)行引用，所以以最后改變的值為準(zhǔn)。

對(duì)象的排序：本文主要闡述對(duì)存儲(chǔ)datatable的list進(jìn)行按TableName排序

1、新建一個(gè)sort類

復(fù)制代碼代碼如下:

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);即可對(duì)list進(jìn)行排序；

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