2007年9月小记

1、GridView导出Excel

StringWriter sw = new StringWriter();

HtmlTextWriter hw = new HtmlTextWriter(sw);

this.grvColumnLogList.RenderControl(hw);

Response.Clear();

Response.ContentType = "application/vnd.ms-excel";

Response.Charset = "utf-8";

Page.EnableViewState = false;

Response.AppendHeader("Content-Disposition", "attachment;filename=MyExcel.xls");

Response.Write("<html><head><meta http-equiv=Content-Type content=\"text/html; charset=utf-8\"><title>Copyright by CJB</title></head><body><center>");

Response.Write(sw.ToString());

Response.Write("</center></body></html>");

Response.End();

需要添加以下override

public override void VerifyRenderingInServerForm(Control control)

{

}

http://www.cnblogs.com/stswordman/archive/2006/08/24/485641.html
http://www.cnblogs.com/powerlc/archive/2005/08/27/223989.html

2、CheckBoxList的全选。

function doSelectThis(cbl)

{

var flag = true;

var iterms = cbl.getElementsByTagName('input');

for(i=0; i<iterms.length;i++)

{

if(!iterms[i].checked)

{

flag = false;

}

var cb = $get('<%= chbAllSelected.ClientID %>');

cb.checked = flag ? true : false;

}

function doSelectAll(obj)

{

var cbl = $get('<%= cblColumns.ClientID %>');

var iterms = cbl.getElementsByTagName('input');

for(i=0; i<iterms.length;i++)

{

if(iterms[i].getAttribute('type') == 'checkbox')

{

iterms[i].checked = obj.checked ? true : false;

}

</script>

<asp:CheckBoxList ID="cblColumns" runat="server" RepeatColumns="5" RepeatDirection="Horizontal" onclick="doSelectThis(this)" ></asp:CheckBoxList>

<asp:CheckBox ID="chbAllSelected" runat="server" Text="全选" onclick="doSelectAll(this);" />

3、固定form的action，避免在多段URL重写的无刷新分页中出现404错误

Sys.Application.add_load(function()

{

var form = Sys.WebForms.PageRequestManager.getInstance()._form;

var href = window.location.href;

form._initialAction = href;

form.action = href;

});

4、302与301对搜索引擎的影响。
301 redirect: 301代表永久性转移(Permanently Moved)，301重定向是网页更改地址后对搜索引擎友好的最好方法，只要不是暂时搬移的情况,都建议使用301来做转址。
302 redirect: 302代表暂时性转移(Temporarily Moved )，在前些年，不少Black Hat SEO曾广泛应用这项技术作弊，目前，各大主要搜索引擎均加强了打击力度，象Google前些年对Business.com以及近来对BMW德国网站的惩罚。即使网站客观上不是spam，也很容易被搜寻引擎容易误判为spam而遭到惩罚。
而Response.Redirect方法返回的正是302，如果对于永久性移除的URL，并且希望它在SEC的记录转移到新的URL中，需要改为301重写向
例如：

protected void Page_Load(object sender, EventArgs e)

{

RedirectPermanently("Page1.aspx");

}

public void RedirectPermanently(string url)

{

HttpContext context = HttpContext.Current;

context.Response.Status = "301 Moved Permanently";

context.Response.AddHeader("Location", ResolveUrl(url));

context.Response.End();

}

5、如何利用客户端缓存对网站进行优化?

protected void Page_Load(object sender, EventArgs e)

{

int secondsTime = 10;

if (Request.Headers["If-Modified-Since"] != null &&

TimeSpan.FromTicks(DateTime.Now.Ticks - DateTime.Parse(Request.Headers["If-Modified-Since"]).Ticks).Seconds < secondsTime)

{

Response.Write(DateTime.Now);

Response.StatusCode = 304;

//Response.Headers.Add("Content-Encoding", "gzip");

Response.StatusDescription = "Not Modified";

}

else

{

Response.Write(DateTime.Now);

SetClientCaching(Response, DateTime.Now);

}

private void SetClientCaching(HttpResponse response, DateTime lastModified)

{

response.Cache.SetETag(lastModified.Ticks.ToString());

response.Cache.SetLastModified(lastModified);

response.Cache.SetCacheability(HttpCacheability.Public);

response.Cache.SetMaxAge(new TimeSpan(7, 0, 0, 0));

response.Cache.SetSlidingExpiration(true);

}

private void SetFileCaching(HttpResponse response, string fileName)

{

response.AddFileDependency(fileName);

response.Cache.SetETagFromFileDependencies();

response.Cache.SetLastModifiedFromFileDependencies();

response.Cache.SetCacheability(HttpCacheability.Public);

response.Cache.SetMaxAge(new TimeSpan(7, 0, 0, 0));

response.Cache.SetSlidingExpiration(true);

}

7、在SQL2005里如何清空事务日志文件？
先把数据库属性改成“简单”，然后收缩日志文件

8、获取随机记录
select * from table order by newid()