Ajax - 500 Internal Server Error

Question

I am trying to learn AJAX for this project at work  I have a site that loads medications that a patient is taking   I call this AJAX function up recursively so that it will append a new table containing a single medication and 7 days worth of history  I am having issues getting the code to execute in FF and IE  Works perfectly fine in chrome  I had alerts displaying the xmlhttp status and this is what I got      xmlhttp status  500  internal server   error     I commented out all of my recursion so it is narrowed down to this tid bit of code    x keeps track of the number of meds so i know when to stop    function LoadMeds       if   x    MaxMedCount             document getElementById  the day   value   parseInt document getElementById  the day   value  7         if   x     MaxMedCount - 1              document getElementById  x   value   x   1        show          else             if  window XMLHttpRequest            code for IE7   Firefox  Chrome  Opera  Safari           xmlhttp new XMLHttpRequest                  else           code for IE6  IE5           xmlhttp new ActiveXObject  Microsoft XMLHTTP                  xmlhttp onreadystatechange function                     try                                  if  xmlhttp readyState  4  amp  amp  xmlhttp status  200                                         var div   document createElement  div                      div innerHTML  xmlhttp responseText                    document getElementById  MedTable   appendChild div                     document getElementById  the med    value   the med                                           catch e                            alert  Error                                xmlhttp open  GET   URL with variables passed  true         xmlhttp send               document getElementById  x   value   x   1         if more code is needed just let me know

User · Answer

One must use behavior  JsonRequestBehavior AllowGet in Post Json Return in C

User · Answer

I had the same error  It turns out that the cause was that the back end method was expecting different json data  In my Ajax call i had something like this     ajax           async  false          type   POST           url   http   13 82 13 196 api aspx PostAjax           data     url   test             contentType   application json  charset utf-8           dataType   json             Now in my WebMethod  inside my C  backend code i had declared my endpoint like this   public static string PostAjax AjaxSettings settings    Where AjaxSettings was declared   public class AjaxSettings       public string url   get  set        The problem then was that the mapping between my ajax call and my back-end endpoint was not the same  As soon as i changed my ajax call to the following  it all worked well   var data     url   test           ajax       async  false      type   POST       url   http   13 82 13 196 api aspx PostAjax       data     settings    data          contentType   application json  charset utf-8       dataType   json        I had to change the data variable inside the Ajax call in order to match the method signature exactly

User · Answer

Had the very same problem  then I remembered that for security reasons ASP doesn t expose the entire error or stack trace when accessing your site service remotely  same as not being able to test a  asmx web service remotely  so I remoted into the sever and monitored my dev tools  and only then did I get the notorious message  Could not load file or assembly  Newtonsoft Json  Version 3 5 0 0  Culture neutral  PublicKeyToken 30ad4fe6b2a6aeed  or one of its dep       So log on the server and debug from there

User · Answer

I fixed an error like this changing the places of the routes in routes php  for example i had something like this   Route  resource  Mensajes    MensajeriaController    Route  get  Mensajes modificar    MensajeriaController modificarEstado      and then I put it like this   Route  get  Mensajes modificar    MensajeriaController modificarEstado    Route  resource  Mensajes    MensajeriaController

User · Answer

The 500  internal server error  means something went wrong on the server s side   It could be several things  but I would start by verifying that the URL and parameters are correct   Also  make sure that whatever handles the request is expecting the request as a GET and not a POST   One useful way to learn more about what s going on is to use a tool like Fiddler which will let you watch all HTTP requests and responses so you can see exactly what you re sending and the server is responding with   If you don t have a compelling reason to write your own Ajax code  you would be far better off using a library that handles the Ajax interactions for you   jQuery is one option

User · Answer

Uncomment the following line    System Web Script Services ScriptService   Service will start working fine          WebService Namespace    http   tempuri org           WebServiceBinding ConformsTo   WsiProfiles BasicProfile1 1          To allow this Web Service to be called from script  using ASP NET   AJAX   uncomment the following line     System Web Script Services ScriptService   public class WebService   System Web Services WebService

User · Answer

This may be an incorrect parameter to your SOAP call  look at the format of the parameter s  in the  data   json section - this is the payload you are passing over - parameter and data wrapped in JSON format   Google Chrome s debugging toolbar has some good tools to verify parameters and look at error messages - for example  start with the Console tab and click on the URL which errors or click on the network tab   You will want to view the message s headers  response etc

User · Answer

I think your return string data is very long  so the JSON format has been corrupted  You should change the max size for JSON data in this way    Open the Web Config file and paste these lines into the configuration section   lt system web extensions gt     lt scripting gt       lt webServices gt         lt jsonSerialization maxJsonLength  50000000   gt       lt  webServices gt     lt  scripting gt   lt  system web extensions gt

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