.NET开发：坚持学asp.net——(十二)

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坚持学asp.net——(十二)

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对象和结构化的数据

集合

作为集合的数组：下面是一个简单的例子：
<%@Page Language="c#" %>
<script runat="server" Language="c#">
void Page_Load()
{
    string[] AnimalArray = new string[5]
                           { "Dog", "Cat", "Elephant", "Lion", "Cat"};
    MyLabel.Text = AnimalArray.GetValue(2).ToString()+"<font color=red> "+Array.IndexOf(AnimalArray,"Cat")+"</font>";
}
</script>
<html>
<asp:label id="MyLabel" runat="server" />
</html>

这个程序输出显然是：Elephant。

下面是一个对数组中某处遍历的程序：
<%@Page Language="c#" %>
<script runat="server" Language="c#">
void Page_Load()
{
    int intCounter = -1;
    string[] AnimalArray = new string[5]
                { "Dog", "Cat", "Elephant", "Lion", "Cat"};
    do
    {
      intCounter = Array.IndexOf(AnimalArray, "Cat", intCounter+1);
      MyText.InnerHtml += "AnimalArray[" + intCounter + "]<br/>";
    } while (intCounter != Array.LastIndexOf(AnimalArray, "Cat"));
}
</script>
<html>
The string "Cat" occurs in the following elements:
<br/>
<div id="MyText" runat="server" />
</html>

颠倒数组中元素的顺序：Array.Reverse(Array1);
将元素排序：Array.Sort(Array1);

使用数组：

<%@Page Language="c#" %>
<script runat="server" Language="c#">
void Page_Load()
{
    string[] AnimalArray = new string[5]
                 { "Dog", "Cat", "Elephant", "Lion", "Cat" };
    Array.Reverse(AnimalArray);
    foreach (string strAnimal in AnimalArray)
    {
      MyDropDownList.Items.Add(strAnimal);
    }
}
</script>
<html>
<form id="Form1" method="post" runat="server">
<asp:dropdownlist id="MyDropDownList" runat="server" />
</form>
</html>

数据绑定：
集合的通用功能是：添加一对语句就可以将集合指定为数据源。
如前面的程序：

MyDropDownList.DataSource=AnimalArray;
MyDropDownList.DataBind();

ArrayList

定义：ArrayLins MyArrayList=new ArrayList();
每一个新项都会自动添加到公文的末尾！
前面的程序可以修改成这样：

<%@Page Language="c#" %>
<script runat="server" Language="c#">
void Page_Load()
{
    ArrayList AnimalArrayList = new ArrayList();
    AnimalArrayList.Add("Dog");
    AnimalArrayList.Add("Cat");
    AnimalArrayList.Add("Elephant");
    AnimalArrayList.Add("Lion");
    AnimalArrayList.Add("Cat");
    MyDropDownList.DataSource = AnimalArrayList;
    MyDropDownList.DataBind();
}
</script>
<html>
<form id="Form1" method="post" runat="server">
<asp:dropdownlist id="MyDropDownList" runat="server" />
</form>
</html>
ArrayList的一些方法：
添加：
MyArrayList.Add(“pig“);
插入：
MyArrayList.Insert(3,“long“);
删除：
MyArrayList.RemoveAt(3);
OR
MyArrayList.Remove(“cat“);

HashTable

创建HashTable:HashTable myHashTable=new HashTable();

添加值的两种方式：
myHashTable.Add([UK],“HongKong“);
OR
myHashTable[UK]=“Hongkong“;

Hashtable.Add() 采用两个参数，一个用于键，一个用于值。两者都属于类型对象。为键传递的值是整数，因此必须将其装箱以便作为对象进行传递。为值传递的值是字符串，它是引用类型，因此不对字符串进行装箱。每答对一个得一分。

e.g.:
<%@Page Language="c#" debug="true" %>
<script runat="server" Language="c#">
void Page_Load(object source, EventArgs e)
{
    Hashtable myHashtable = new Hashtable();
    myHashtable["UK"] = "United Kingdom";
    myHashtable["US"] = "United States";
    myHashtable["DE"] = "Germany";
    if (!(Page.IsPostBack))
    {
      foreach (DictionaryEntry Item in myHashtable)
      {
        ListItem newListItem = new ListItem();
        newListItem.Text = Item.Value.ToString();
        newListItem.Value = Item.Key.ToString();
        myDropDownList.Items.Add(newListItem);
      }
    }
}
void Click(object source, EventArgs e)
{
    myLabel.Text = myDropDownList.SelectedItem.Value;
}
</script>
<html>
<form runat="server">
    <asp:dropdownlist id="myDropDownList" runat="server" />
    <asp:button id="myButton" runat="server" text="OK" Onclick="Click" />
    <br /><br />
    <asp:Label id="myLabel" runat="server" text="" />
</form>
</html>

SortedList

类似HashTable，其中的值排序按照健值排序，而不是值！
使用：
<%@Page Language="c#" debug="true" %>
<script runat="server" Language="c#">
void Page_Load(object source, EventArgs e)
{
    SortedList mySortedList = new SortedList();
    mySortedList["armadillo"]="any of a family ... small bony plates";
    mySortedList["amaryllis"]="an autumn-flowering ... Hippeastrum or Sprekelia]";
    mySortedList["zebra"]="any of several fleet ... white or buff";
    mySortedList["artichoke"]="a tall composite herb ... cooked as a vegetable";
    if (!(Page.IsPostBack))
    {
      foreach (DictionaryEntry Item in mySortedList)
      {
        ListItem newListItem = new ListItem();
        newListItem.Text = Item.Key.ToString();
        newListItem.Value = Item.Value.ToString();
        myDropDownList.Items.Add(newListItem);
      }
    }
}
void Click(object source, EventArgs e)
{
    myLabel.Text = myDropDownList.SelectedItem.Value;
}
</script>
<html>
<form runat="server">
    Pick a word from the list:
    <asp:dropdownlist id="myDropDownList" runat="server" />
    <asp:button id="myButton" runat="server" text="OK" Onclick="Click" />
    <br /><br />
    <b>Definition: </b>
    <asp:Label id="myLabel" runat="server" text="" />
</form>
</html>

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