Setting Session Variable in JavaScript returns assigned variable in WebMethod

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QamarMo-8446 asked Mar 3, '22 LanHuang-MSFT commented Mar 4, '22

Setting Session Variable in JavaScript returns assigned variable in WebMethod

How do I get the value of a Session Variable set in JavaScript in a WebMethod?

JavaScript:
var img = new Image();
img.src = obj.imageData;
'<%Session["ImgSrc1"] = "' + img.src+'"; %>';

var canvas = document.getElementById("cnv");
var imgX = canvas.toDataURL("image/png");
<%Session["ImgSrc2"] = "'+ imgX +'";%> ;

WebMethod:
string sImage1 = HttpContext.Current.Session["ImgSrc1"].ToString(); // values[10];
string sImage2 = HttpContext.Current.Session["ImgSrc2"].ToString(); // values[10];

sImage1 returns '+ img.src+'
sImage2 returns '+ imgX +'

dotnet-aspnet-general dotnet-aspnet-webforms dotnet-aspnet-webpages

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AgaveJoe · Mar 03 at 10:54 AM

How do I get the value of a Session Variable set in JavaScript in a WebMethod?

JavaScript cannot set a Session variable directly. JavaScript runs in the browser while Session exists on the server. Use AJAX to sent an HTTP request to set Session on the server.

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QamarMo-8446 AgaveJoe · Mar 03 at 01:02 PM

I can set a Sessions variable as the following and it works fine in WebMethod:
'<%Session["CurrentDate"] = txtFirstName.Value; %>';

But, the same won't work if I assign a variable to txtFirstName.Value and pass it to the Session.

Do you have a sample code or reference to try AJAX to send an HTTP request to set Session on the server?

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Answer 1 · 2022-03-03T08:46:26.193Z

LanHuang-MSFT answered Mar 3, '22 LanHuang-MSFT edited Mar 4, '22

Hi @QamarMo-8446,
In the JavaScript function, use XmlHt tpRe quest to make an AJ AX call to the SetSe ssion WebMethod and send the values to the WebMethod.
The WebMethod then returns a string, which is displayed using a JavaSc ript al ert message box.
Here is the example.179622-345.txt
EDIT
179925-front.txt
code behind

  public static void UploadImage(string imageData)
         {          
             byte[] data = Convert.FromBase64String(imageData);
             Document pdfDoc = new Document();         
             var output = new FileStream(HttpContext.Current.Server.MapPath("2.pdf"), FileMode.Create);
             PdfWriter writer = PdfWriter.GetInstance(pdfDoc, output);
             pdfDoc.Open();
             iTextSharp.text.Image img = iTextSharp.text.Image.GetInstance(data);
              pdfDoc.Add(img);
              pdfDoc.Close();           
         }    
         protected void Button1_Click1(object sender, EventArgs e)
         {
             Process.Start(Server.MapPath("2.pdf"));
         }

Best regards,
Lan Huang

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1.jpg (119.9 KiB)

1.jpg (99.7 KiB)

345.txt (1.3 KiB)

front.txt (2.1 KiB)

8.gif (142.6 KiB)

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QamarMo-8446 · Mar 03 at 01:37 PM

Hi,
I already have the code that you provided and that part works for my other Input (type=text) controls.
But, I have not been able to figure out how to pass an image object obj.imageData to request.send()

var img = new Image();
img.src = obj.imageData;

Basically, I have a page with several textbox controls and a Canvas control that already has a signature in it.
I can create a pdf all labels and textbox control values but I have not been able to get the signature from the Canvas
The has signature in it - This part works fine.
Now, I want to add signature to the pdf

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AgaveJoe QamarMo-8446 · Mar 03 at 02:07 PM

If I understand, this question has nothing to do with Session??? You want to upload an image using AJAX???

https://stackoverflow.com/questions/13198131/how-to-save-an-html5-canvas-as-an-image-on-a-server

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Answer 2 · 2022-03-03T13:25:45.823Z

AgaveJoe answered Mar 3, '22

I can set a Sessions variable as the following and it works fine in WebMethod:
'<%Session["CurrentDate"] = txtFirstName.Value; %>';

Correct it's also not possible to set Session from a text input value from Web method. ASPX Web Method are static and therefore cannot reference instance members and ASMX web services do not have a UI.

Do you have a sample code or reference to try AJAX to send an HTTP request to set Session on the server?

You did not tell us if you are working with an ASPX Web Method or ASMX Web Method. I'll assume ASPX. With either you must enable Session as Session is not turned on by default.

 [WebMethod(EnableSession = true)]
 public static string MyFunction(string jstring)
 {
     HttpContext.Current.Session["jstring"] = jstring;
     return "You send " + jstring;
 }

AJAX has the following pattern.

capture.png (21.9 KiB)

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Answer 3 · 2022-03-03T14:25:00.367Z

QamarMo-8446 answered Mar 3, '22 LanHuang-MSFT commented Mar 4, '22

I am using aspx.
I have been able to move a bit forward and now I can save the Canvas signature in WebMethod.
string imageData = values[10];
string fileNameWitPath = @"C:\temp\" + DateTime.Now.ToString().Replace("/", "-").Replace(" ", "- ").Replace(":", "") + ".png";
using (FileStream fs = new FileStream(fileNameWitPath, FileMode.Create))
{
using (BinaryWriter bw = new BinaryWriter(fs))

             {
                 byte[] data = Convert.FromBase64StringimageData 
                 //byte[] data = Convert.FromBase64String(imageData);
                 bw.Write(data);
                 bw.Close();
             }
         }

Now, I need to figure out how to use byte[] data to add to pdf

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AgaveJoe · Mar 03 at 04:22 PM

Now, I need to figure out how to use byte[] data to add to pdf

You'll need to read the documentation for the PDF library you are using.

Keep in mind, you've asked three different question in this thread. Organize your thoughts and create a new posts with all the information a forum member needs to debug your code.

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LanHuang-MSFT · Mar 04 at 04:41 AM

Hi @QamarMo-8446,
I've modified my answer for your new needs, you can check it out.
If you have a new question, please open a new post.
Best regards,
Lan Huang

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Answer 4 · 2022-03-03T16:57:39.157Z

QamarMo-8446 answered Mar 3, '22 AgaveJoe commented Mar 3, '22

You are right but
It has been very difficult to post these questions; I get Permission Denied error. In fact, I posted a question on this error and asked why I was getting the error but no one responded.

Now I it allows me to post but ONLY sometimes and without using the option "Code Sample"

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AgaveJoe · Mar 03 at 09:29 PM

While I realize not being able to post JavaScript is painful it does not stop you from following the advice given and posting a screenshot of the JavaScript or a text file. Sharing incomplete and poorly formatted code forces the community to guess how your code works.

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