Question

环境：.Net 3.5，jQuery 2.1.4

结果Hello, World会在回调中返回，但有没有办法让它作为附件返回？

jquery的：

function test() {
    $.ajax({
        type: "POST",
        url: "Handler1.ashx",
        contentType: "application/json; charset=utf-8",
        success: function (data) {
            $('#progressBar').hide();
            //alert(data);                
        }
    });

通用处理程序：

public class Handler1 : IHttpHandler
    {

        public void ProcessRequest(HttpContext context)
        {
            //Create and populate a memorystream with the contents of the 
            //database table 
            System.IO.MemoryStream mstream = GetData();
            //Convert the memorystream to an array of bytes. 
            byte[] byteArray = mstream.ToArray();
            //Clean up the memory stream 
            mstream.Flush();
            mstream.Close();
            // Clear all content output from the buffer stream 
            context.Response.Clear();
            // Add a HTTP header to the output stream that specifies the default filename 
            // for the browser's download dialog 
            context.Response.AddHeader("Content-Disposition", "attachment; filename=mytextfile.txt");
            // Add a HTTP header to the output stream that contains the 
            // content length(File Size). This lets the browser know how much data is being transfered 
            context.Response.AddHeader("Content-Length", byteArray.Length.ToString());
            // Set the HTTP MIME type of the output stream 
            context.Response.ContentType = "application/octet-stream";
            // Write the data out to the client. 
            context.Response.BinaryWrite(byteArray);
        }

        private MemoryStream GetData()
        {
            //Create the return memorystream object that will hold 
            //the buffered data. 
            MemoryStream ReturnStream = new MemoryStream();
            try
            {
                Thread.Sleep(5000); //Simulate some work.

                StreamWriter sw = new StreamWriter(ReturnStream);

                //Write the row of data to the Memory Stream. 
                sw.WriteLine("Hello, World");

                //Clean up the stream writer 
                sw.Flush();
                sw.Close();
            }
            catch (Exception Ex)
            {
                throw Ex;
            }
            //Return the memory Stream 
            return ReturnStream;
        }

        public bool IsReusable
        {
            get
            {
                return false;
            }
        }
    }

资源：
http://www.c-sharpcorner.com/article/downloading-data-as-a-file-from-a-memorystream-using-a-http/

Answer 1

jQuery ajax无法正确处理二进制响应（无法设置） responseType），所以最好使用普通的XMLHttpRequest调用

var xhr = new XMLHttpRequest();
xhr.open('POST', "Handler1.ashx", true);
xhr.responseType = 'arraybuffer';
xhr.onload = function ()
{
    if (this.status === 200)
    {
        var filename = "";
        var disposition = xhr.getResponseHeader('Content-Disposition');
        if (disposition && disposition.indexOf('attachment') !== -1)
        {
            var filenameRegex = /filename[^;=\n]*=((['"]).*?\2|[^;\n]*)/;
            var matches = filenameRegex.exec(disposition);
            if (matches != null && matches[1]) filename = matches[1].replace(/['"]/g, '');
        }
        var type = xhr.getResponseHeader('Content-Type');

        var blob = new Blob([this.response], { type: type });
        if (typeof window.navigator.msSaveBlob !== 'undefined')
        {
            // IE workaround for "HTML7007: One or more blob URLs were revoked by closing the blob for which they were created. These URLs will no longer resolve as the data backing the URL has been freed."
            window.navigator.msSaveBlob(blob, filename);
        }
        else
        {
            var URL = window.URL || window.webkitURL;
            var downloadUrl = URL.createObjectURL(blob);

            if (filename)
            {
                // use HTML5 a[download] attribute to specify filename
                var a = document.createElement("a");
                // safari doesn't support this yet
                if (typeof a.download === 'undefined')
                {
                    window.location = downloadUrl;
                }
                else
                {
                    a.href = downloadUrl;
                    a.download = filename;
                    document.body.appendChild(a);
                    a.click();
                }
            }
            else
            {
                window.location = downloadUrl;
            }

            setTimeout(function () { URL.revokeObjectURL(downloadUrl); }, 100); // cleanup
        }
    }
    else
    {
        // Handle Error Here
    }
};
xhr.setRequestHeader('Content-type', 'application/x-www-form-urlencoded');
xhr.send($.param($(frm).serializeArray()));
}

<强> You can get more help here :-)

使用jquery，通用处理程序和等待状态下载文件

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