How to catch every exception thrown in a webmethod but without those exceptions interrupting the execution of the program - asp.net

Is there any way I can make that every exception thrown inside a webmethod go straight to the jQuery Ajax error callback function?
$.ajax({
type: "POST",
contentType: "application/json; charset=utf-8",
url: "MantenimientoNotasCapacidades.aspx/SaveViaWebService",
data: JSON.stringify(params),
dataType: "json",
async: true,
success: function (data) {
},
error: function (request, status, error) {
var response = JSON.parse(request.responseText).d;
var error = JSON.parse(response);
alert(JSON.parse(request.responseText).error.message);
}
});
I know that using JSON.parse(request.responseText).Message should be enough to show the information for that error but all I've got now is that every time an exception is raised the code stops right there , being necessary to keep pressing F10 or F5 to finally be able to see the alert.
I already tried enclosing my code in a 'try' block but I don't see much point in doing that since I can't do much in the 'catch' block as I'd do in a visual basic application where I could use the 'catch' block to show the exception message in a MsgBox.
Is there any way to catch in the error callback function all the exceptions thrown in a webmethod but without them stopping the execution of the code?
Any help would be much appreciated.
P.S. Happy new year!!

Following #cmd.promt's advice, I changed the Response.StatusCode to 500 and created and object(myError) containing the description for the exception that was thrown, then the only thing left to do was to serialize the object and send it back to the client (Here I tried to use Response..Write("{""message"": ""action failed!""}") but for some reason I always ended up getting the same error : "JSON.parse: unexpected non-whitespace character after JSON data" so in the end I decided to go with json.net and forget all about response.Write)
<WebMethod()> _
Public Shared Function SaveViaWebService(lst As List(Of Students)) As String
Try
Catch ex As Exception
Dim httpResponse = HttpContext.Current.Response
httpResponse.Clear()
httpResponse.StatusCode = 500
'I thought that .StatusDescription would be useful but it turned out it didn't
'httpResponse.StatusDescription = ex.Message
Dim myError= New With {.message = ex.Message, .source = ex.Source}
Return JsonConvert.SerializeObject(myError)
End Try
End Function
And with that, the error is correctly sent to the error callback , where the only thing I had to do was to play with firebug and see how the error has been sent
$.ajax({
type: "POST",
contentType: "application/json; charset=utf-8",
url: "MantenimientoNotasCapacidades.aspx/SaveViaWebService",
data: JSON.stringify(params),
dataType: "json",
async: true,
success: function (data) {
},
error: function (request, status, error) {
var response = JSON.parse(request.responseText).d;
var error = JSON.parse(response);
alert(JSON.parse(request.responseText).error.message);
}
});
Thus far, everything is as I as wanted it , except for the exceptions that keep on interrupting the execution of the program. Is that their normal behaviour ?? Aren't they all supposed to go directly to the 'catch' block??

Related

ASP.Net, jQuery, Ajax and a parseError

I have tried to see if there is anything on this great site for this (and there probably is), so I am sorry if I have missed it.
Anyway, I am calling a WCF endpoint using jQuery Ajax under ASP.Net.
The Web service call is working fine in Fiddler and returns the following data:
{"d": {"__type":"ProcessedTotals:#","DailyError":"0","DailyProcessed":"0","TotalError":"48","TotalProcessed":"70"}}
This is my code
function GetData() {
alert('Ajax Start');
$.ajax({
dataType: "jsonp",
data: "{}",
contentType: "json",
url: "http://localhost/abc123/WebManagement.svc/ReturnTotals",
success: (function (data) {
alert(data[0].TotalProcessed);
//$("#TotRecs").html(data.d.TotalProcessed);
//$("#TotErr").html(data.d.TotalError);
//$("#DayTot").html(data.d.DailyProcessed);
//$("#DayErr").html(data.d.DailyError);
}),
error: function (xhr, status, error) {
alert("FAILED:" + status);
}
})
alert('Ajax End');
}
Whilst debugging in Firefox the line that causes the error is SUCCESS:
I know that it is using JSONP, as I am having to access the data from a different website.
Thanks
Paul
$.ajax({
dataType: "jsonp",
url: "http://localhost/abc123/WebManagement.svc/ReturnTotals",
success: (function (data) {
console.log(data);
})
});
You were doing some weird stuff there. Trying to send an empty object literal along with the call, which doesn't make any sense. Also, your error callback won't work with a jsonp request. Try the above, it should work fine. If not, please mention the error that you're getting.

How to process msg returned from jquery.ajax()

I would like to know what are the properties of msg object from jquery.ajax(). I am throwing an exception inside asp.net static function, but I am unable to cast it in javascript.
Thanks for help
You can read the response from your .Net page e.g.
$(function(){
$.ajax({
type: 'POST',
url: "test.aspx",
data: "ref=test",
success: function(r) { },
error: function(r) { alert(r.toString()); }
});
});
You can then read the error message and do the necessary steps..
If you have exception in the Server-Side, then JavaScript couldn't catch the Exception cause JavaScript is in the Client-Side.
You can catch the exception by yourself in Server-Side and send a custom error message to Ajax "success function" to handle the error(Exception) you thrown

In ASP.NET with JQuery, how would you define and handle exceptional conditions

I use $.ajax to call a .asmx to get JSON data back. The server side process will meet some exceptional conditions which will give back to client error response for displaying error message.
How would you design the error hanlding mechanism? I mean what would you make server side retrun and let client handle the error?
Thanks.
If it's just an error message (a string), then you can just return that string and set the status to 500 so jQuery recognizes it's not a successful request. Then just use your error handler (or a global .ajaxError() handler for all requests) to do what you want with that message.
For example a simple way to handle all errors like this (instead of per-$.ajax() call) would be:
$(document).ajaxError(function(e, xhr) {
alert("There was an error, server responded with: " + xhr.responseText);
});
ther's an error handler in jquery just like the success function, you need to handle it:
function CallWebService(ParentPage) {
$.ajax({
type: "POST",
url: "../Admission/AdmissionService.asmx/LoadLocations",
data: "{'ParentPage':'" + ParentPage + "'}",
contentType: "application/json; charset=utf-8",
dataType: "json",
success: function (data) {
$('.innerHospitalCensusdiv').html(data.d);
BindSelectLocation();
},**error: function(ex){
//handle error here
}**
});
}

why does the 'error' function of $.ajax execute even when the request to invoke a webmethod succeeds?

I am using jquery ajax method to invoke a webmethod upon clicking a 'span'.This is webmethod is in one of my aspx pages and I am invoking it from the master page using the following code.
$(document).ready(function(){
$("#btn").click(function() {
$.ajax({
type: "POST",
url: "Default.aspx/removedata",
data:"{}",
contentType: "application/json; charset=utf-8",
dataType: "json",
success:function(msg) {
$("li#search").removeClass('current');
$("li#search").addClass('hide');
$("#tabnew").addClass('hide');
window.location="Result.aspx";
},
error:function(xhr, status, error) {
alert("error");
//var err = eval("(" + xhr.responseText + ")");
// Display the specific error raised by the server
//alert(err.Message);
console.log(xhr.statusText);
}
});
});
});
when I click the span I can see the webmethod getting invoked(by debugging ),but even before the webmethod starts executing I get the alert 'error' and I see (an empty string) message being logged into the firebug console.
As far as I know the 'error' function gets executed only if the ajax request fails.But I can see the webmethod getting executed.I do not understand why the error function is executing even then.
Could someone please help me with this.
Thanks
The error handler is executed if the server side script returns an error code different than 200. You could use FireBug to inspect what exactly is happening under the covers.

Simple AJAX not working

I have this AJAX code, but it doesn't seem to throw the 'alert' method. Instead, nothing happens. I looked at it with Fiddler and got this error message:
{"Message":"There was an error processing the request.","StackTrace":"","ExceptionType":""}
I'm trying to call a web method in the code-behind called MyWebMethod:
$.ajax({ type: "POST",
url: "Test.aspx/MyWebMethod",
data: "{" + username + "}",
contentType: "application/json; charset=utf-8",
dataType: "json",
success: function() {
alert("success");
},
fail: function() {
alert("Fail");
}
});
The web method worked fine when I had a script manager on the page, but I want to remove the script manager and thought that using AJAX would be the best way.
Thanks
You have custom errors enabled in the web.config. Therefore, the exception returned will be generic (mostly blank) and the same every time. This makes it difficult to debug.
To see the real exception, temporarily disable custom errors. Here is how to do that for web services only, if you need that granularity.
I think if you change fail to error, you'll get the second alert box.
[Edit] I think if you then change
data: "{" + username + "}"
to
data: "{ 'username': '" + username + "' }"
you'll get the first alert, although it's hard to know that without seeing the service you're calling.

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