The ASP. Net server cannot set the content type after sending the HTTP header

Time:2021-10-9

Problems found:

Export excel with npoi, the foreground page is still ASPX, and then report the error of “failed to receive message from the server”.

Solution:

Error about “the server cannot set the content type after sending the HTTP header”:

      1. Myxls is used to export components

      2. The page adopts ASPX

3. The main contents of the page include:

<form runat="server">
 <asp:ScriptManager ID="Scriptmanager1" runat="server">
 </asp:ScriptManager>
 <asp:UpdatePanel ID="UpdatePanel1" runat="server">
  <ContentTemplate>
   < ASP: button runat = "server" id = "btnexport" text = "export to excel" cssclass = "btn_common" onclick = "btnexport_click" / >
  </ContentTemplate>
 </asp:UpdatePanel>
</form>

If it cannot be exported, the error shown in the title will be reported.

The solution is to add the ability of “global refresh” to btnexport

Add the following code between to solve the problem

<Triggers>
 <% -- < ASP: asyncpostbacktrigger controlid = "" / > -- > <% -- local refresh value refresh UpdatePanel internal --% >
 < ASP: postbacktrigger controlid = "btnexport" / > <% -- refresh all -- > <% -- on July 1, 2016, solve the error of "the server cannot set the content type after sending the HTTP header" when clicking the Export button --% >
</Triggers>

summary

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