How do you catch exceptions from a Web Service that is returning a custom object?
I've seen this post but it doesn't seem to show how to get the exception that was thrown by the service.
I can pull the SOAP Exception, but I want to be able to get the original exception that the web service returned. I've looked at the variables that are set at this time and can't seem to see the exception anywhere, I just see:
"Server was unable to process request. ---> Exception of type
'RestoreCommon.ConsignmentNotFoundException' was thrown."
try
{
Consignment cons = WebServiceRequest.Instance.Service
.getConsignmentDetails(txtConsignmentNumber.Text);
lblReceiverName.Text = cons.Receiver.Name;
}
catch (ConsignmentNotFoundException)
{
MessageBox.Show("Consignment could not be found!");
}
Is this possible?
In short, no.
Web services will always throw SOAP fault. In your code,
MessageBox meant to be used in Windows forms and nowhere else.
You can throw this exception and in the client application, you will have to handle a SOAP fault.
Edit: If you do not want to send exceptions across to the client, this what you could do:
class BaseResponse
{
public bool HasErrors
{
get;
set;
}
public Collection<String> Errors
{
get;
set;
}
}
Each WebMethod response must inherit from this class. Now, this is how your WebMethod blocks would look like:
public ConcreteResponse SomeWebMethod()
{
ConcreteResponse response = new ConcreteResponse();
try
{
// Processing here
}
catch (Exception exception)
{
// Log the actual exception details somewhere
// Replace the exception with user friendly message
response.HasErrors = true;
response.Errors = new Collection<string>();
response.Errors[0] = exception.Message;
}
finally
{
// Clean ups here
}
return response;
}
This is just an example. You may need to write proper exception handling code rather than simply using generic catch block.
Note: This will take care of exceptions occurring in your application only. Any exceptions occurring during communication between client and service, will still be thrown to the client application.
Related
I'm using RestSharp to communicate with a REST-Server and wrote a small wrapper function for the call
private T Get<T>(string restAdress) where T : new()
{
try
{
// throw new Exception(); // This one is caught
IRestClient restClient = new RestClient(settings.Value.HostToConnect).UseSerializer(new JsonNetSerializer()); // (1)
RestRequest restRequest = new RestRequest(restAdress);
IRestResponse<T> result = restClient.Get<T>(restRequest); // (2)
return result.Data;
}
catch (Exception e) // debugger wont stop here
{
// debugger wont stop here too
// code within this block is not executed
}
return null; // (3)
}
Since I want to use the Newtonsoft-Attributes I give in a custom (de)serializer (1).
public class JsonNetSerializer : IRestSerializer
{
public string Serialize(object obj) =>
JsonConvert.SerializeObject(obj);
public string Serialize(RestSharp.Parameter bodyParameter) =>
JsonConvert.SerializeObject(bodyParameter.Value);
public T Deserialize<T>(IRestResponse response) =>
JsonConvert.DeserializeObject<T>(response.Content); // (4)
public string[] SupportedContentTypes { get; } =
{
"application/json", "text/json", "text/x-json", "text/javascript", "*+json"
};
public string ContentType { get; set; } = "application/json";
public DataFormat DataFormat { get; } = DataFormat.Json;
}
When calling the REST service and trying to get the result (2) an Exception is thrown if the deserialization fails (4). But the Exception is not caught by the try-catch block. I tried to debug but after throwing the debugger goes on in line (3), the catch and the logging withing the catch is never executed. The debugger won't even stop at the catch (Exception e) it goes straight from (4) to (3).
(Sorry for not english, the title of the window says "Exception User-Unhandled")
Can anyone explain this behaviour to me?
Whats happening here is an interesting setting of the debugger, another example would be this closed bug report. When the debugger reaches the point the exception is thrown it will break, causing the behaviour you experienced.
If you uncheck the exception setting "Break when this exception type is user-unhandled" in the dialog, you should be able to reach your catch block, as the debugger no longer breaks the execution as soon as the specified exception is thrown.
In your case you find that option under "Ausnahmeeinstellungen".
I am maintaining RestSharp, so I hope I can answer this.
RestSharp doesn't throw on deserialisation by default. If you look at the code, deserialisation happens in the private IRestResponse<T> Deserialize<T>(IRestRequest request, IRestResponse raw) method of RestClient.
When RestSharp can't deserialise the response, it creates an error response. You get the response status set to Error and the exception is put into the ErrorException property of the response object, along with the exception message that gets to the ErrorMessage of the response.
It is still possible to tell RestSharp to throw on deserialisation if you assign the FailOnDeserialization property of the RestClient instance to true.
How property handle errors in Dropbox C# SDK?
I want to use common method for handling errors from different API calls. This method should be used on top app level and in serevals API calls. For most clouds API (like Microsoft OneDrive and Google Drive API) I can do it because there is strictly defined list (enum will all error codes) and only one exception class for error handling.
But in Dropbox C# SDK everything is contrariwise! There's no any error code list but there are dozen exception class (one exception template Dropbox.Api.ApiException<T> and great amount of errors object for T template parameter). Look for example on count of error classes for files operation - http://dropbox.github.io/dropbox-sdk-dotnet/html/N_Dropbox_Api_Files.htm
What the hell! How handle all of them ? Write giant catch() block ?
And worse, most of them use the same errors types!
For example, class Dropbox.Api.Files.LookupError that describes errors like "Not found", "Malformed Path" and so on is part of 21! others errors classes. For handling the simple "Not found" error I must be able to catch two dozen exceptions! Is it normal?
So, how property handle errors in Dropbox C# SDK?
If you want to catch any arbitrary Dropbox exception, instead of handling specific ones, you can catch the parent type DropboxException, like this:
try {
var account = await this.client.Users.GetCurrentAccountAsync();
// use account
} catch (DropboxException ex) {
// inspect and handle ex as desired
}
try {
var list = await client.Files.ListFolderAsync(string.Empty);
// use list
} catch (DropboxException ex) {
// inspect and handle ex as desired
}
try {
var download = await client.Files.DownloadAsync(path);
// use download
} catch (DropboxException ex) {
// inspect and handle ex as desired
}
Here's a more complete example showing how to catch a specific exception, and also how to inspect an exception caught generally:
try {
var list = await client.Files.ListFolderAsync(string.Empty);
// use list
} catch (ApiException<Dropbox.Api.Files.ListFolderError> ex) {
// handle ListFolder-specific error
} catch (DropboxException ex) {
// inspect and handle ex as desired
if (ex is AuthException) {
// handle AuthException, which can happen on any call
if (((AuthException)ex).ErrorResponse.IsInvalidAccessToken) {
// handle invalid access token case
}
} else if (ex is HttpException) {
// handle HttpException, which can happen on any call
}
}
I'm using C# to build a service operation. When something goes wrong, I want to throw an exception that could be catch client side.
However, when an exception is thrown the client is only able to get a generic error like "400: bad request" and the exception message is not accessible.
In my service operation, I have enabled verbose errors with this:
[ServiceBehavior(IncludeExceptionDetailInFaults = true)]
and
config.useVerboseErrors = true;
I also unpack the TargetInvocationException and instead return a DataServiceException with this function:
protected override void HandleException(HandleExceptionArgs args)
{
// Handle exceptions raised in service operations.
if (args.Exception.GetType() == typeof(TargetInvocationException)
&& args.Exception.InnerException != null)
{
if (args.Exception.InnerException.GetType() == typeof(DataServiceException))
{
// Unpack the DataServiceException.
args.UseVerboseErrors = true;
args.Exception = args.Exception.InnerException as DataServiceException;
}
else
{
// Return a new DataServiceException as "400: bad request."
args.UseVerboseErrors = true;
args.Exception = new DataServiceException(400, args.Exception.InnerException.Message);
}
}
}
When I use the browser, I can see the verbose exception message, but when I try programmatically, the inner exception is null and I only see the generic error message "400: bad request".
Strangely, if I return a code 200 instead of 400, I can see the exception message in the answer body. But obviously I don't want to do this.
So, is there a way to get the exception message client side, when you throw an exception from a service operation?
Have you had a look at end to end tracing? Furthermore, this MSDN page isn't as daunting as it may first seem, and i think the "Provide Additional Information When an Exception Occurs" section would be useful to you. Have a lovely read.
An exception occurs on line
ModifyProfileResp resp = BFGlobal.modifyProfile(req);
INTERNAL_ERROR, SoapHeaderException was unhandled
Error: System.Exception._COMPlusExceptionCode -532462766,
This code basically updates the users information on a web service through a call I made.
public ModifyProfileResp ModifyProfile(string n_homeTelephone)
{
try
{
// Get Login Resp
LoginResp loginResp = LoginToBetfair("username", "password");
// Make a BFGS instance
BFGlobal = new BFGlobalService();
// Set up the request in [req]
ModifyProfileReq req = new ModifyProfileReq();
req.header = new APIRequestHeader();
req.header.sessionToken = loginResp.header.sessionToken;
req.homeTelephone = n_homeTelephone;
// Set up the response in [resp]
// Here is where Im getting thrown an exception..
ModifyProfileResp resp = BFGlobal.modifyProfile(req); // <-- Here Im getting thrown an exception
// return [resp] - which is the response from the call
// Just trying to print out errror codes
string mec = resp.minorErrorCode.ToString();
string ec = resp.errorCode.ToString();
return resp;
}
catch (Exception)
{
throw;
}
Pretty straightforward, make the request header, call the response, pass in the req and I should get some data back, but I keep getting thrown a exception on this line.
Any ideas on how to go about this?
First,
don't do this:
catch (Exception)
{
throw;
}
It's pointless. If you don't have the catch the exception will automatically get thrown up a level, which is what you're doing with throw. Further, if you can't do something with the exception (like retry the request) you're probably better off letting the exception bubble up.
Second, try something like this:
catch (SoapHeaderException ex)
{
Debug.WriteLine(ex.Message);
}
This will catch the specific exception that you're dealing with. Further, set a breakpoint here on the Debug statement. You can then browse the details of the exception. You'll be able to see the stacktrace, inner exceptions and any other data that the thrower of the SoapHeaderException might want you to see.
This information can often be useful when you're debugging, for example, it could say "You forgot to initialize the flux capacitor."
You're seeing an exception from the remote web service.
SoapHeaderException Class
The exception that is thrown when an XML Web service method is called over SOAP and an exception occurs during processing of the SOAP header.
Likely you're not setting up your headers as the remote service requires. Try to acquire help from the remote side.
Try viewing the .InnerException for more details.
I have a server-side WCF RIA Service that is intentionally throwing an exception because the user entered an invalid value. This exception comes across the wire, however, I can't figure out how to catch it. I currently have the following code:
try
{
DomainContext.CalculateRequest(OnCalculateCompleted, null);
}
catch (Exception ex)
{
MessageBox.Show("here");
}
...
private void OnCalculateCompleted(InvokeOperation response)
{
try
{
if (response.HasError == false)
{
// Do stuff with result
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
How do I handle exceptions thrown by a server-side operation on the client side? None of my catch statements are being triggered. Thank you!
On the client side the InvokeOperation.HasErrors will be true and you can get the Exception object from the InvokeOperation.Error. Note, if you handled the error you should also call MarkErrorAsHandled().
Your OnCalculateCompleted might looks something like this.
private void OnCalculateCompleted(InvokeOperation response)
{
if (response.HasError == false)
{
// Do stuff with result
}
else
{
MessageBox.Show(response.Error.Message);
response.MarkErrorAsHandled();
}
}
Yes, because in the callback (OnCalculateCompleted), exception will not be marshalled. The exception will reside in the response.Error property.
But take care, because your server-side thrown exception will NOT be found in the response.Error!
You should override your DomainService's OnError method, package your server-side exception via errorcodes or something, and on the client (SL) side, you have to unpack it again.