在asp.net页面中经常会出现一些ViewState的html标记，也许某些时候你会禁用ViewState，但是某些情况下你不得不使用它——因为它的便捷性，但是由于在默认情况下，ViewState的HTML标记总是在页面的最前面，而且都是一些没有意义的内容，一般的搜索引擎收录的时候 就会将这些无意义的字符串收录进去，这样就会严重影响你所制作的网页在搜索引擎的排名。有没有解决办法？答案是有的，可以将ViewState的Html标记移到底部，不影响性能，对搜索引擎更友好。这种方法就是重写页面的Render，将ViewState的Html标记移到底部。
原始页面的HTML：
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Top.aspx.cs" Inherits="Admin_Top" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>调整ViewState的位置，让你的asp.net页面对搜索引擎更友好</title>
</head>
<body>
<form id="form1" runat="server">
<div>
</div>
</form>
</body>
</html>
<head runat="server">
<title>调整ViewState的位置，让你的asp.net页面对搜索引擎更友好</title>
</head>
<body>
<form id="form1" runat="server">
<div>
</div>
</form>
</body>
</html>
这个页面后台没有任何业务cs代码的情况下，得到的HTML代码如下：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head><title>
调整ViewState的位置，让你的asp.net页面对搜索引擎更友好
</title></head>
<body>
<form name="form1" method="post" action="Top.aspx" id="form1">
<div>
<input type="hidden" name="__VIEWSTATE" id="__VIEWSTATE" value="/wEPDwUJNzgzNDMwNTMzZGTKRk3xYdpqlKIfqyg44evx9dxYpQ==" />
</div>
</div>
</form>
</body>
</html>
<head><title>
调整ViewState的位置，让你的asp.net页面对搜索引擎更友好
</title></head>
<body>
<form name="form1" method="post" action="Top.aspx" id="form1">
<div>
<input type="hidden" name="__VIEWSTATE" id="__VIEWSTATE" value="/wEPDwUJNzgzNDMwNTMzZGTKRk3xYdpqlKIfqyg44evx9dxYpQ==" />
</div>
<div>
</div>
</form>
</body>
</html>
现在不改变前台aspx代码，重写Render方法，后台cs代码如下：
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Text.RegularExpressions;
using System.Text; public partial class Admin_Top : System.Web.UI.Page
{
//ViewState的Html标记的正则表达式
private static readonly Regex viewStateRegex = new Regex(@"(<input type=""hidden"" name=""__VIEWSTATE"" id=""__VIEWSTATE"" value=""[w+//=]+"" />)", RegexOptions.Multiline | RegexOptions.Compiled);
//</form>标记的正则表达式
private static readonly Regex endFormRegex = new Regex(@"</form>", RegexOptions.Multiline | RegexOptions.Compiled);
{
System.IO.StringWriter stringWriter = new System.IO.StringWriter();
HtmlTextWriter htmlWriter = new HtmlTextWriter(stringWriter);
base.Render(htmlWriter);
Match viewStateMatch = viewStateRegex.Match(html);
string viewStateString = viewStateMatch.Captures[0].Value;//找出ViewState的Html标记
html = html.Remove(viewStateMatch.Index, viewStateMatch.Length);//替换掉ViewState的html标记
Match endFormMath = endFormRegex.Match(html, viewStateMatch.Index);
html = html.Insert(endFormMath.Index, viewStateString);//将ViewState的Html标记插入到</form>标记之前
writer.Write(html);
}
protected void Page_Load(object sender, EventArgs e)
{
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Text.RegularExpressions;
using System.Text; public partial class Admin_Top : System.Web.UI.Page
{
//ViewState的Html标记的正则表达式
private static readonly Regex viewStateRegex = new Regex(@"(<input type=""hidden"" name=""__VIEWSTATE"" id=""__VIEWSTATE"" value=""[w+//=]+"" />)", RegexOptions.Multiline | RegexOptions.Compiled);
//</form>标记的正则表达式
private static readonly Regex endFormRegex = new Regex(@"</form>", RegexOptions.Multiline | RegexOptions.Compiled);
protected override void Render(HtmlTextWriter writer)
{
System.IO.StringWriter stringWriter = new System.IO.StringWriter();
HtmlTextWriter htmlWriter = new HtmlTextWriter(stringWriter);
base.Render(htmlWriter);
string html = stringWriter.ToString();
Match viewStateMatch = viewStateRegex.Match(html);
string viewStateString = viewStateMatch.Captures[0].Value;//找出ViewState的Html标记
html = html.Remove(viewStateMatch.Index, viewStateMatch.Length);//替换掉ViewState的html标记
Match endFormMath = endFormRegex.Match(html, viewStateMatch.Index);
html = html.Insert(endFormMath.Index, viewStateString);//将ViewState的Html标记插入到</form>标记之前
writer.Write(html);
}
protected void Page_Load(object sender, EventArgs e)
{
}
}
最后生成的Html页面的代码：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head><title>
调整ViewState的位置，让你的asp.net页面对搜索引擎更友好
</title></head>
<body>
<form name="form1" method="post" action="Top.aspx" id="form1">
<div> </div>
</div>
<input type="hidden" name="__VIEWSTATE" id="__VIEWSTATE" value="/wEPDwUJNzgzNDMwNTMzZGTKRk3xYdpqlKIfqyg44evx9dxYpQ==" /></form>
</body>
</html>
<head><title>
调整ViewState的位置，让你的asp.net页面对搜索引擎更友好
</title></head>
<body>
<form name="form1" method="post" action="Top.aspx" id="form1">
<div> </div>
<div>
</div>
<input type="hidden" name="__VIEWSTATE" id="__VIEWSTATE" value="/wEPDwUJNzgzNDMwNTMzZGTKRk3xYdpqlKIfqyg44evx9dxYpQ==" /></form>
</body>
</html>
最后的结果大家也看到了，确实移动了ViewState的html标记的位置，这样对搜索引擎更友好。