How to send querystring value via Ajax call to Handler page

Question

I want to pass querystring value obtained from current page to Handler.ashx page via Ajax call using script below? At present it is passing nothing value to handler.
<script>
var counter;

     function UploadFile() {  

     
         var files = $("#<%=imageUpload.ClientID%>").get(0).files;  
        counter = 0;  
        // Loop through files  
        for (var i = 0; i < files.length ; i++) {  
            var file = files[i];  
            var formdata = new FormData();  
            formdata.append("file1", file);  
            var ajax = new XMLHttpRequest();  
       

            ajax.upload.addEventListener("progress", progressHandler, false);  
            ajax.addEventListener("load", completeHandler, false);  
            ajax.addEventListener("error", errorHandler, false);  
            ajax.addEventListener("abort", abortHandler, false);  
            **ajax.open("POST", "FileUploadHandler.ashx?ID='" + <%=Request.QueryString.Get("PK_ID")%> + "'" );**  
              
            ajax.send(formdata);  
           

Public Class FileUploadHandler : Implements IHttpHandler

Public Sub ProcessRequest(ByVal context As HttpContext) Implements IHttpHandler.ProcessRequest  
      
    Dim test As String = context.Request.Params("PK_ID")

Answer 1

Hi @peter liles ,
The first is the problem of the ID not matching the PK_ID parameters, and also to confirm whether <% = Request.QueryString.Get( " PK_ID " ) % > has a value
I suggest you to break the point to check the problem, you can refer to my example below:

Sub ProcessRequest(ByVal context As HttpContext) Implements IHttpHandler.ProcessRequest  
  
        context.Response.ContentType = "text/plain"  
        Dim file As String = context.Request.Params("ID")  
        context.Response.Write(file)  
  
    End Sub  

---

Public PK_ID As String = "1"  
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load  
  
    End Sub  

---

Best regards,
Lan Huang

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Answer 2

After reading your example and testing i came to the understanding that my querystring was incorrect in the handler! i converted it to integer as i normal do. But in this instance it would not accept only in string format?
I scrapped the idea of utilizing javascript to upload files. Mainly because a requirement was to also update images in gridview.
Only reason i decided to try Javascript was because it came with a progress meter example and i discovered was not possible with a UpdatePanel approach?
I stumbled across a solution to that problem using scriptmanager handler!