坚持学asp.net——(十二)
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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