服务器不能在发送了c# excel内联的HTTP标头后追加标头
本文关键字:HTTP 追加 excel 不能 服务器 | 更新日期: 2023-09-27 17:53:27
我有这个问题,试图返回一个excel内联响应。
我搜索了所有的帮助编码页面的答案,不能找到一些工作。
我在下面做了一个简单的例子。这个问题总是会发生。
本行错误:
Line 56: Response.AddHeader("content-disposition",
背后的代码:
public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
PleaseWait();
Call();
}
protected void Call()
{
strSql = "SELECT * FROM ....... ; ";
SqlCommand cmd = new SqlCommand(strSql);
DataTable dt = GetData(cmd);
GridView GridView1 = new GridView();
GridView1.AllowPaging = false;
GridView1.DataSource = dt;
GridView1.DataBind();
Response.Clear();
Response.Buffer = true;
Response.BufferOutput = true;
Response.ClearHeaders();
Response.AddHeader("content-disposition",
"attachment;filename= "Output.xls");
Response.Charset = "";
Response.ContentType = "application/vnd.ms-excel";
StringWriter sw = new StringWriter();
HtmlTextWriter hw = new HtmlTextWriter(sw);
for (int i = 0; i < GridView1.Rows.Count; i++)
{
GridView1.Rows[i].Attributes.Add("class", "textmode");
}
GridView1.RenderControl(hw);
string style = @"<style> .textmode { mso-number-format:'@; } </style>";
Response.Write(style);
Response.Output.Write(sw.ToString());
Response.Flush();
Response.End();
}
protected void PleaseWait()
{
this.Response.Write("<meta http-equiv=X-UA-Compatible content=IE=8>");
this.Response.Write(@"<style type=text/css media=all>");
this.Response.Write(@".loading");
this.Response.Write(@"{");
this.Response.Write(@"text-align: center;");
this.Response.Write(@"padding-top: 30px;");
this.Response.Write(@"border-width: 1px solid #000;");
this.Response.Write(@"width: 300px;");
this.Response.Write(@"height: 100px;");
this.Response.Write(@"-ms-filter: alpha(opacity=90);");
this.Response.Write(@"-ms-opacity: 0.90;");
this.Response.Write(@"border-style: solid;");
this.Response.Write(@"background-color: #FFFFFF;");
this.Response.Write(@"position: absolute;");
this.Response.Write(@"font-family: Trebuchet MS;");
this.Response.Write(@"font-size: small;");
this.Response.Write(@"position: absolute;");
this.Response.Write(@"top: 0;");
this.Response.Write(@"bottom: 0;");
this.Response.Write(@"left: 0;");
this.Response.Write(@"right: 0;");
this.Response.Write(@"margin: auto;");
this.Response.Write(@"display: block;");
this.Response.Write(@"background: url('images/wait01.gif') no-repeat center;");
this.Response.Write(@"}");
this.Response.Write(@"</style>");
this.Response.Write(@"<div id=mydiv class=loading> </div>");
this.Response.Write(@"<script>mydiv.innerText = '';");
this.Response.Write(@"</script>");
this.Response.Write(@"<script language=javascript>;");
this.Response.Write(@"var dots = 0;");
this.Response.Write(@"var dotmax = 10;");
this.Response.Write(@"function ShowWait()");
this.Response.Write(@"{");
this.Response.Write(@"var output;");
this.Response.Write(@"output = 'Wait...';");
this.Response.Write(@"dots++;");
this.Response.Write(@"if(dots>=dotmax)dots=1;");
this.Response.Write(@"for(var x = 0;");
this.Response.Write(@"x < dots;x++)");
this.Response.Write(@"{");
this.Response.Write(@"output += '.';");
this.Response.Write(@"}");
this.Response.Write(@"mydiv.innerText = output;");
this.Response.Write(@"}");
this.Response.Write(@"function StartShowWait()");
this.Response.Write(@"{");
this.Response.Write(@"mydiv.style.visibility = 'visible'; ");
this.Response.Write(@"window.setInterval('ShowWait()',1500);");
this.Response.Write(@"}");
this.Response.Write(@"function HideWait()");
this.Response.Write(@"{");
this.Response.Write(@"mydiv.style.visibility = 'hidden';");
this.Response.Write(@"window.clearInterval();");
this.Response.Write(@"}");
this.Response.Write(@"StartShowWait();");
this.Response.Write(@"</script>");
this.Response.Flush();
Thread.Sleep(500);
}
private DataTable GetData(SqlCommand cmd)
{
DataTable dt = new DataTable();
String strConnString = System.Configuration.ConfigurationManager.
ConnectionStrings["conn"].ConnectionString;
SqlConnection con = new SqlConnection(strConnString);
SqlDataAdapter sda = new SqlDataAdapter();
cmd.CommandType = CommandType.Text;
cmd.Connection = con;
try
{
con.Open();
sda.SelectCommand = cmd;
sda.Fill(dt);
return dt;
}
catch (Exception ex)
{
throw ex;
}
finally
{
con.Close();
sda.Dispose();
con.Dispose();
}
}
public override void VerifyRenderingInServerForm(Control control)
{
}
}
是的,你不能那样做。在PleaseWait
方法中,你调用了Response.Flush
。它发送当前缓冲的输出以及HTTP头。HTTP报头总是在其他响应数据之前发送,所以你就不走运了。
通常的方法是有一个单独的PleaseWait
页,它做一个定时重定向到实际的文件(然后只发送文件数据与适当的头)。
基本问题是HTTP是"单个请求,单个响应"。您试图对单个请求返回两个响应,而这在纯HTTP上是不可能的(遗憾的是;有一些类似http的协议允许这样做,但浏览器并不真正支持它们——当你可以一次发送20个文件,而不是在20个单独的请求中发送时,这是一个很大的性能提升。