Getting Error: 500 Internal server error when using AJAX POST to C# Webmethod

Question

var image = document.getElementById("capture").toDataURL("image/png");
image = image.replace('data:image/png;base64,', '');

alert(image);

        $.ajax({
            type: 'POST',
            url: 'Info.aspx/testingPOST',
            data: '{ "imageData" : "' + image + '" }',
            contentType: 'application/json; charset=utf-8',
            dataType: 'json',
            success: function(response, textStatus, jqXHR) {
                alert("File Saved");
            },
            error: function (jqXHR, exception) {
    var msg = 'error';
    if (jqXHR.status === 0) {
        msg = 'Not connect.\n Verify Network.';
    } else if (jqXHR.status == 404) {
        msg = 'Requested page not found. [404]';
    } else if (jqXHR.status == 500) {
        msg = 'Internal Server Error [500].';
    } else if (exception === 'parsererror') {
        msg = 'Requested JSON parse failed.';
    } else if (exception === 'timeout') {
        msg = 'Time out error.';
    } else if (exception === 'abort') {
        msg = 'Ajax request aborted.';
    } else {
        msg = 'Uncaught Error.\n' + jqXHR.responseText;
    }
    alert("error:" + msg);
    }
            })
        }

Using the above to post my canvas image to the Webmethod and then just a simple check in c# below. I am getting error 500. I have looked on various posts and can't seem to find any tweak that gets this working, I have turned off the auto-redirect in app_start and various other suggestions. But still nothing.

[WebMethod]
    public static bool testingPOST(string value)
    {
        
        return true;
    }

To start, you need to configure your server app to report the full details of the error so you have a better idea of what's wrong. — Jasen
– Jasen, Commented Nov 30, 2021 at 0:23
try to change data: '{ "imageData" : "' + image + '" }' to data: { value : image }, — cura
– cura, Commented Nov 30, 2021 at 0:29
The 500 error details are hidden by default for security reasons. It should be disabled for production servers. The details on how to do this varies depending on the app technology -- so you really need to search for a specific setup (and sometimes version). — Jasen
– Jasen, Commented Nov 30, 2021 at 0:34
I am currently using in the webconfig <httpErrors errorMode="Detailed" /> <asp scriptErrorSentToBrowser="true"/> but only getting 500 error in the details in the browser — n00ms
– n00ms, Commented Nov 30, 2021 at 10:00

n00ms · Accepted Answer · 2021-11-30 15:38:42Z

1

I used the developer tools in Google Chrome, and clicked on the error, then on preview.. it showed me that the json string length was too long.

I edited the webconfig with the following and it now works!

<system.web.extensions> 
<scripting> 
<webServices> 
<jsonSerialization maxJsonLength="500000000"/>
 </webServices> 
</scripting> 
</system.web.extensions>

answered Nov 30, 2021 at 15:38

n00ms

211 silver badge4 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

CorrieJanse · Accepted Answer · 2021-11-30 00:29:06Z

0

WebMethod tells the applicaiton it is accessed through and XML WebService request. if you want to access it through POST you will need the ScriptMethod attribute:

[ScriptMethod]
public static bool testingPOST(string value)
{
    return true;
}

See this answer for more info:

what is web method attribute in web service?

answered Nov 30, 2021 at 0:29

CorrieJanse

2,5981 gold badge10 silver badges31 bronze badges

2 Comments

n00ms Over a year ago

Still getting the 500 error using this change.

n00ms Over a year ago

[Webmethod] was required, when I changed it to [Scriptmethod] I would get an error that there was a missing web method

Collectives™ on Stack Overflow

Getting Error: 500 Internal server error when using AJAX POST to C# Webmethod

2 Answers 2

Comments

2 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related