Send byte array from code behind to ajax call

Question

I have a web method in which I convert a HTML to PDF and then save it to a local folder, I want the user to download that file without making a post back, so I'm trying to make an AJAX POST call into a web method to get the byte array and then convert it into a PDF, the problem is that I get an error 500:

{Message: "There was an error processing the request.", StackTrace: "", ExceptionType: ""}

Although I know the web method triggers, because when placing a breakpoints it stops there and I can actually see the binary array before the return as well as the created file on the folder, I still get the error massage, here is my code:

C#:

[WebMethod]
public static byte[] getfile(string one, string two)
{
    HttpContext context = HttpContext.Current;
    HtmlToPdf converter = new HtmlToPdf();

    converter.Options.MinPageLoadTime = 10;
    converter.Options.MaxPageLoadTime = 30;

    PdfDocument doc = converter.ConvertUrl("http://localhost/dashboard_pdf.aspx?one=" + one+ "&" + "two=" + two);

    string appPath = HttpContext.Current.Request.ApplicationPath;
    Random rnd = new Random();
    int num = rnd.Next(1, 1000000);
    string path = context.Server.MapPath(appPath + "/Web/" + num + ".pdf");

    doc.Save(path);   
    doc.Close();

    FileStream stream = File.OpenRead(path);
    byte[] fileBytes = new byte[stream.Length];

    stream.Read(fileBytes, 0, fileBytes.Length);
    stream.Close();

    byte[] b1 = System.IO.File.ReadAllBytes(path);

    return fileBytes;
}

JS:

$.ajax({
    type: "POST",
    url: "dashboard.aspx/getfile",
    contentType: "application/json; charset=utf-8",
    data: "{'one':\"" + one+ "\", 'two':\"" + two + "\" }",
    dataType: "json",
    processData: false,
    success: function (data) {
        data = data.d;

        var byteArray = new Uint8Array(data);
        var a = window.document.createElement('a');

        a.href = window.URL.createObjectURL(new Blob([byteArray], { type: 'application/pdf' }));

        a.download = "Dashboard";

        document.body.appendChild(a)
        a.click();
        document.body.removeChild(a)
    }
});

Any ideas?

Thanks.

dataType shouldn't be "json" and I don't think it supports bytes. You probably want to use a different api. — Crowcoder
– Crowcoder, Commented Oct 8, 2018 at 20:57
I know for sure that this method should work, because this is practically a copy paste from a method that I have converting a word file into a byte array, the difference is that in this case the file is located in a folder, my other method has the file in the DB, that's why I don't know why this in particular doesn't work. — elunap
– elunap, Commented Oct 8, 2018 at 21:03

elunap · Accepted Answer · 2018-10-08 21:28:40Z

1

I solve this by adding this into my web.config:

 <system.web.extensions>
    <scripting>
      <webServices>
        <!-- Update this value to change the value to a larger value that can accommodate your JSON Strings -->
        <jsonSerialization maxJsonLength="86753090" />
      </webServices>
    </scripting>
  </system.web.extensions>

answered Oct 8, 2018 at 21:28

elunap

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befree2j · Accepted Answer · 2020-10-12 08:46:36Z

0

 var jsonResult = Json(model, JsonRequestBehavior.AllowGet);
            jsonResult.MaxJsonLength = int.MaxValue;
            return jsonResult;

In this way you return the maximum byte array and can be able to convert to PDF and download

answered Oct 12, 2020 at 8:46

befree2j

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