有关动态声明对象问题!(微软专家和各位大侠请进:))在线相候......

申明一个新对象???if(userName=="")
{yourClassname ttttt=new yourClassname();}
elseif
{yourClassname bbbbb=new yourClassname();}
elseif
{yourClassname ddddd=new yourClassname();}

解决方案 »

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是动态的做如下声明：
Public MyLabel As System.Web.UI.WebControls.Label根据需要Public不同的服务器端控件，如何实现？
这是典型的Fatcory模式，请看：
NameFactory.cs
using System;namespace Factory
{
public class Namer{
protected string last;
protected string first;

public string getFirst(){
return first;
}

public string getLast(){
return last;
}
}

public class FirstFirst: Namer{

public FirstFirst(string s){
int i = s.LastIndexOf(" ");
if(i > 0){
first = s.Substring(0,i).Trim();
last  = s.Substring(i+1).Trim();
}
else{
first = "";
last  = s;
}
}
} public class LastFirst: Namer{
public LastFirst(string s){
int i = s.IndexOf(",");
if(i > 0){
last  = s.Substring(0,i).Trim();
first = s.Substring(i+1).Trim();
}
else{
last  = s;
first = "";
}
}
}

public class NameFactory{
public Namer getNamer(string entry){
int i = entry.IndexOf(",");
if(i>0){
return new LastFirst(entry);
}
else{
return new FirstFirst(entry);
}
}
}
}FactoryClient.cs
using System;
using Factory;public class FactoryClient{ public static void Main(string[] Args)
{
string name = "";
while((name.Trim()).Length == 0){
name = Console.ReadLine();
} NameFactory nf = new NameFactory();
Namer n = nf.getNamer(name);

Console.WriteLine(n.getFirst() + " " + n.getLast());
}
}
文件名:datagrid.aspx<%@ Page Language="vb" AutoEventWireup="false" Codebehind="datagrid.aspx.vb" Inherits="eg_lesson.datagrid"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
<HEAD>
<title>datagrid</title>
<meta content="Microsoft Visual Studio .NET 7.0" name="GENERATOR">
<meta content="Visual Basic 7.0" name="CODE_LANGUAGE">
<meta content="JavaScript" name="vs_defaultClientScript">
<meta content="http://schemas.microsoft.com/intellisense/ie5" name="vs_targetSchema">
</HEAD>
<body MS_POSITIONING="GridLayout">
<form id="Form1" method="post" runat="server">
<FONT face="宋体"></FONT>
<DIV id="disply" style="Z-INDEX: 102; LEFT: 232px; WIDTH: 208px; POSITION: absolute; TOP: 32px; HEIGHT: 144px" runat="server"></DIV>
<FONT face="宋体"></FONT><FONT face="宋体"></FONT><FONT face="宋体"></FONT><FONT face="宋体">
</FONT>
</form>
</body>
</HTML>=============================================
'datagrid.aspx.vbImports System.Web.UI.HtmlControls
Imports System.Data
Imports System.Data.SqlClient
Public Class datagrid
    Inherits System.Web.UI.Page
    ' Protected WithEvents disply As System.Web.UI.HtmlControls.HtmlGenericControl#Region " Web 窗体设计器生成的代码 "    '该调用是 Web 窗体设计器所必需的。
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()    End Sub    Private Sub Page_Init(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Init
        'CODEGEN: 此方法调用是 Web 窗体设计器所必需的
        '不要使用代码编辑器修改它。
        InitializeComponent()
    End Sub#End Region    Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        '在此处放置初始化页的用户代码
        Dim disply As System.Web.UI.HtmlControls.HtmlGenericControl
        Dim DataGrid1 As New System.Web.UI.WebControls.DataGrid()
        disply.Controls.Add(DataGrid1)  '将DataGrid控件动态加入到Div元素中
        Dim conn As New SqlConnection()
        '连接数据库字符串
        conn.ConnectionString = "data source=(local);initial catalog=ga;password=lovesong;user id=sa"
        conn.Open()
        Dim strSel As String
        strSel = "select * from tbl_pcs"
        'SqlDataAdapter是在DataSet与关系数据库间起桥梁作用
        Dim objDataAdapter As New SqlDataAdapter(strSel, conn)
        Dim objDataSet As New DataSet()
        objDataAdapter.Fill(objDataSet, "pcs")
        DataGrid1.DataSource = objDataSet.Tables("pcs").DefaultView  '为DataGrid控件指定数据源
        DataGrid1.AllowPaging = True    '是否允许分页属性
        DataGrid1.PageSize = "10"       '每页的数量
        ' DataGrid1.PagerStyle.Mode = PagerMode.NumericPages   '确定分页用数字表示页码
        '指定用一个自定义格式作为前后页跳转
        DataGrid1.PagerStyle.NextPageText = "Next"  '这和PagerMode.NumericPages属性只能选择其一
        DataGrid1.PagerStyle.PrevPageText = "Prev"
        Response.Write(DataGrid1.PageCount)        '写出DataGrid总共有多少页
        ' DataGrid1.Columns[0].HeaderText = "ID号"
        ' DataGrid1.Columns(0)
        AddHandler DataGrid1.PageIndexChanged, AddressOf LogGridPage  'AddHandler语句将事件进行绑定
        DataGrid1.DataBind()    End Sub
    Sub LogGridPage(ByVal sender As System.Object, ByVal e As DataGridPageChangedEventArgs)
        sender.CurrentPageIndex = e.NewPageIndex
        sender.DataBind()
    End SubEnd Class
在datagrid.aspx里有以下服务端控件
<DIV id="disply" style="Z-INDEX: 102; LEFT: 232px; WIDTH: 208px; POSITION: absolute; TOP: 32px; HEIGHT: 144px" runat="server"></DIV>
我将在Public里声明的disply 注释
' Protected WithEvents disply As System.Web.UI.HtmlControls.HtmlGenericControl
放到PageLoad里
Dim disply As System.Web.UI.HtmlControls.HtmlGenericControl
然后运行会报以下错误:未将对象引用设置到对象的实例。 disply.Controls.Add(DataGrid1)  '将DataGrid控件动态加入到Div元素中
难道不可以放到子程序里定义?
to evonne_feng(evonne) :
兄弟我不理解,可否做下解释??
to  jackyhx(飞不动的侠)
我加入了以下两句报了值不能为空。参数名：child 的错.
        Dim disply As System.Web.UI.HtmlControls.HtmlGenericControl
        Me.Controls(1).Controls.Add(disply)不知是何原因????
使用 PlaceHolder 控件可能更好。
将 "<div>内容</div>"整个添加到 PlaceHolder的 Controls 中去。
to spring_ok(spring.z):
        Dim disply As System.Web.UI.HtmlControls.HtmlGenericControl
        Dim objControls As New PlaceHolder()
        objControls.Controls.Add(disply)还是报原来一样的错误
值不能为空。参数名：child
有谁能告诉我为什么吗????
跑题了吧？怎么到placeholder那了？有关系么？
to  jackyhx(飞不动的侠)：
可否解释一下Me.Controls(1).Controls.Add(disply)中的controls(1)是什么意思和起什么作用？
可否解释一下Me.Controls(1).Controls.Add(disply)中的controls(1)是什么意思和起什么作用？
this.Controls[1]  is  System.Web.UI.HtmlControls.HtmlForm
you use
Response.Write(this.Controls[1].ToString());see url
http://www.csdn.net/expert/topic/914/914057.xml?temp=.1204492
能否说说this.controls(1)中的数据是按什么顺弃来排列的呢?
按照aspx文件里控件假如的顺序，需要说明的是，有些服务端控件还包含一个
“子”控件
怎没见到微软专家呢？？？？？？？能否解决一下关于.net里.aspx页和codebhind的后头代码之间关系问题。比如说：在后台代码定义一个控件，通过了编译。在.aspx页里进行修改后不进行重新生成过程。在.aspx里的控件还会接受编译吗？