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I am trying to allow users to download a file, and have been trying for quite a while to no avail to get this to work. The code I have been using is:

Response.ClearHeaders();
Response.Clear();
Response.BufferOutput = true;
Response.AddHeader("Content-disposition", 
                    "attachment; filename= "+ Path.GetFileName(path) + fileType);                     
Response.ContentType = "application/octet-stream";
Response.BinaryWrite(buffer);
Response.Flush();
Response.Close();
Response.End();

Unfortunately nothing happens when I try to make it run except for lots of exceptions:

A first chance exception of type 'System.Web.HttpException' occurred in System.Web.dll
A first chance exception of type 'System.Web.HttpException' occurred in System.Web.Mvc.dll
A first chance exception of type 'System.Web.HttpException' occurred in System.Web.Mvc.dll
A first chance exception of type 'System.NullReferenceException' occurred in WebDev.WebHost40.dll

(etc)

Changing my debugging settings I discovered that the exception I was getting was

"Server cannot set content type after HTTP headers have been sent."

I have searched through Google and attempted many solutions but nothing have worked so far. This is the only time Response has been used as far as I know - unless there is some background processes occurring (if so, how do I change this?). Please note that I am using Asp.NET MVC.

Any ideas?

Edit: Here is some context, which might help to resolve the problem:

The code is inside a Webmethod that has been called via Ajax, the reason being that I needed to call the server side via the client side (bad practice, but it was needed in the time provided) and I also needed to pass through a parameter.

Here is the ajax call:

$("#Button").each(function() { 
                this.submitting = false; //To prevent double-clicking problems
            }).on("click", function (e) {
                if (e.preventDefault) e.preventDefault();
                $.ajaxSetup({ cache: false });
                e.preventDefault();
                 if (!this.submitting) 
                { 
                    this.submitting = true; 
                    var self = this; 
                    $.ajax({
                        url: 'Controller/retrieveFile',
                        type: 'POST',
                        data: { SystemNumber: $("#Button").val() },
                        dataType: 'json',
                        success: function (data) {
                            self.submitting = false; 
                        },
                        error:  function() { 
                            self.submitting = false; 
                        } 
                    });
                }
            });

Is this, perhaps, a problem with the return value? Currently I am returning 

Json(true, JsonRequestBehavior.AllowGet);
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1 に答える 1

0

HttpContext.Response.AppendHeader("Content-disposition", ....) を使用して、Response.ClearHeaders(); を削除してみてください。および Response.Clear(); 行。

また、メソッドの戻り値の型として FileContentResult を使用することを検討する必要があります。

于 2012-12-05T12:18:54.933 に答える