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  • Migrating from OCS 2007 R2 to Lync: Part 2

    In the story so far, Johan has described how to check that the migration from your OCS to Lync is supported and how to determine the requirements for the new installation This was followed by a walk-through of the preparation the Active Directory and installation of the first Lync Front End Server with a Mediation Server co-located. Now Johan tackles the merging the OCS configuration, and connection to the outsode world, followed by testing, performing and then validating the migration.

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  • Pidgin to pidgin, what protocol to chose?

    - by Johan
    Hi I and a friend need to start to use some instant messaging and it seem like pidgin is a nice program to use. However it supports quite a lot of different protocols. So my question is witch to choose? Since both parties can use the same program we don't have to use the same protocol as "all the rest", but can focus on what is best to use. As a side note both parties will be using Ubuntu based computers. Thanks Johan

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  • How do I read old star office 5.x spreadcheet documents today? (*.sdc)

    - by Johan
    Hi I found a couple of old spreadsheet documents that I created a couple of years ago that I would like to read again. I think I used the old Star Office 5.2 to create those Spreadsheets. They all have names like *.sdc I have tried to use Open Office to open them, but he can't recognise what it is. Does anybody have any idea how I can open those documents? Thanks Johan

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  • GAE Django template and swedish characters

    - by fredrik
    Hi, I'm trying to render templates of an html-page that contains swedish characters "åäö" but when it renders in the web browser it ends up with "?". The page renders in UTF-8. Is there any way to workaround this or do I need to write the chars as html-code? Also any pointers to the best support for multi-lang site? ..fredrik

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  • Use a JSON array with objects with javascript

    - by Fredrik Johansson
    Hi, I have a function that will get a JSON array with objects. In the function I will be able to loop through the array, access a property and use that property. Like this: Variable that I will pass to the function will look like this: [{"id":28,"Title":"Sweden"}, {"id":56,"Title":"USA"}, {"id":89,"Title":"England"}] function test(myJSON) { // maybe parse my the JSON variable? // and then I want to loop through it and access my IDs and my titles } Any suggestions how I can solve it? Regards, Fredrik

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  • What software can I use to read png metadata?

    - by Johan
    I know that I can create a simple little Qt based application that adds and read png metadata, using the QImage.setText(...) and QImage.text(...). That metadata can then be read with a linux command called pngmeta. But what other image software can I use to read out the png metadata? Please note that I'm seeking image programs for the common platforms, so please specify if your application is for Windows or Linux. To make the question clearer I attached a img with some test metadata attached to it. Thanks Johan Links: http://en.wikipedia.org/wiki/Portable_Network_Graphics - png http://en.wikipedia.org/wiki/Extensible_Metadata_Platform - xmp metadata

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  • How to get started with tcp/ip v6?

    - by Johan
    Hi Now and then there is "news" about that the ip numbers will run out in X years, and we must change to tcp/ip v6... And even thou this crisis never really happens it has waken a question, how do you get started with tcp/ip v6? What can I do at home and is this a good or bad idea? Can you use IPv4 and IPv6 in the same cables in the same LAN, or do you need to physically separate them? Can you have some translation box so you can reach the "normal" internet from the IPv6 connected devices? (Just like a NAT-Router) Can someone please clarify the situation a little bit? Thanks Johan

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  • [xUbuntu] Move a window back into the visible area?

    - by Johan
    Hi I have this annoying little problem on my laptop that sometimes after I have used a external monitor (with higher resolution) some applications place them self outside the visible area of my desktop. So the question is how do I move them back into the visible area? (please note that no part of the window is visible so I can't use the mouse) Is there some app that can give me focus to move a application to the mouse pointer or something like that? Please note that I'm running xUbuntu (xfce) on this laptop. Thanks Johan

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  • iBatis.Net SQL Server Compact Edition 3.5

    - by Johan
    Hi I want to migrate one of our databasis from SQL Server Express to SQL Server Compact 3.5. I'm using iBatis.Net but do not know what the providers.config must look like for me to be able to access SQL CE 3.5. Can anyone help me out with this? Thanks Johan

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  • DirectFB on a Beagleboard

    - by Johan
    Hi I'm thinking about playing with DirectFB on my Beagleboard. Does anybody have some practical pointers on how to get this up and running? What is a good starting point? Thanks Johan

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  • GNU make: should -j equal number the number of CPU cores in a system?

    - by Johan
    Hi What is you experience with the make -j flag? There seem to be some controversial if the jobs are supposed to be equal to the numbers of cores, or if you can maximize the build by adding one extra job that can be cued up while the others "work". The question is if it is better to use -j4 or -j5? And have you seen (or done) any benchmarking that support one or the other? Thanks Johan

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  • z-Index overlay in google maps version 3

    - by fredrik
    Hi, I'm trying to get an overlay in google maps api v3 to appear above all markers. But it seems that the google api always put my overlay with lowest z-index priority. Only solution i've found is to iterate up through the DOM tree and manually set z-index to a higher value. Poor solution. I'm adding my a new div to my overlay with: onclick : function (e) { var index = $(e.target).index(), lngLatXYposition = $.view.overlay.getProjection().fromLatLngToDivPixel(this.getPosition()); icon = this.getIcon(), x = lngLatXYposition.x - icon.anchor.x, y = lngLatXYposition.y - icon.anchor.y $('<div>test</div>').css({ left: x, position: 'absolute', top: y + 'px', zIndex: 1000 }).appendTo('.overlay'); } I've tried every property I could think of while creating my overlay. zIndex, zPriority etc. I'm adding my overlay with: $.view.overlay = new GmapOverlay( { map: view.map.gmap }); And GmapOverlay inherits from new google.maps.OverlayView. Any ideas? ..fredrik

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  • Using memcache to store obj's in google app engine.

    - by fredrik
    Hi, I'm trying to use memcache to cache data retrevied from the datastore. Storing stings works fine. But can't one store an object? I get an error "TypeError: 'str' object is not callable" when trying to store with this: pageData = PageType(page) memcache.add(memcacheid, pageData, 60) I've read in the documentation that it requires "The value type can be any value supported by the Python pickle module for serializing values." But don't really understand what that is. Or how to convert pageData to it. Any ideas? ..fredrik

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  • Why does Visual Studio 2008 change namespace characters in a generated file?

    - by Fredrik
    Hello, I am working on a asp.net 3.5 project in sweden, where some of the namespaces include swedish characters, such as 'å', 'ä' and 'ö'. When building the project and generating the design-file, visual studio replaces these characters with some other strange characters. This only happens when the characters occur in a namespace or class name. If a field or variable contain a swedish character, everything works fine. To clarify, the strange character occur in the design file when a namespace and/or control contain swedish characters. Does anyone know why this happens and if there is a solution for the problem that doesn't mean changing the names of the namespaces? Sincerely, Fredrik

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  • How do I setup FitNesse for use with .NET?

    - by Fredrik
    I'm trying to get started with FitNesse for .NET on Windows Vista. In all tutorials I find on the web I'm told to execute the run.bat file, but all i get when downloading the latest release is a .jar-file. When i run this, the filestructure is unpacked and I can reach the fitnesse server by browsing to http://localhost. Now, when I'm trying to set up a test project, according to all documentation I find I'm supposed define the path to fitsharp.dll but I can't find this file anywhere in the filestructure that was set up from the .jar-file. What am I doing wrong? Sincerely, Fredrik

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  • Error on windows using session from appengine-utilities

    - by fredrik
    Hi, I ran across an odd problem while trying to transfer a project to a windows machine. In my project I use a session handler (http://gaeutilities.appspot.com/session) it works fine on my mac but on windows I get: Traceback (most recent call last): File "C:\Program Files (x86)\Google\google_appengine\google\appengine\ext\webapp_init_.py", line 510, in call handler.get(*groups) File "C:\Development\Byggmax.Affiliate\bmaffiliate\admin.py", line 29, in get session = Session() File "C:\Development\Byggmax.Affiliate\bmaffiliate\appengine_utilities\sessions.py", line 547, in init self.cookie.load(string_cookie) File "C:\Python26\lib\Cookie.py", line 628, in load for k, v in rawdata.items(): AttributeError: 'unicode' object has no attribute 'items' Anyone familiar with the Session Handler that knows anything of this? All help are welcome! ..fredrik

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  • zoom_changed only triggers once in google maps api version 3 using MVC

    - by fredrik
    Hi, I'm trying to use the MVC objects in google maps version 3. What I can't seem to figure out is why my zoom_changed method is only invoked once. When I first load the map the zoom_changed method is invoked. But not when I zoom on the map. function MarkerWidget (options) { this.setValues(options); this.set('zoom', this.map.zoom); var marker = new google.maps.Marker({ icon : this.icon, mouseOverIcon : this.mouseOverIcon, orgIcon : this.orgIcon }); marker.bindTo('map', this); marker.bindTo('position', this); google.maps.event.addListener(marker, 'mouseover', this.onmouseover); google.maps.event.addListener(marker, 'mouseout', this.onmouseout); } MarkerWidget.prototype = new google.maps.MVCObject(); MarkerWidget.prototype.zoom_changed = function () { $.log(this, new Date()); } Shouldn't the map object fire the zoom event and notify all object's that has "this.set('zoom', this.map.zoom)" ? ..fredrik

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  • Using sub filters/queries in Google App Engine

    - by fredrik
    Hi, I'm trying to use figure out how to sub query a query that uses a filter. From what I've figured out so far while using .filter() it changes the original query, that leads to a second .filter() would also have to match the first filter. I would like to make something like this: modules = data.Modules.all().filter('page = ', page.key()) modules.filter('name = ', 'Test') modules.filter('name = ', 'Test2') I can't get the "Test2" filter to work. The only solution I have at the moment is to make all new queries. data.Modules.all().filter('page = ', page.key()).filter('name = ', "Test").get() data.Modules.all().filter('page = ', page.key()).filter('name = ', "Test2").get() Or write the same as an GQL. But for me it seams quite stupid way to go. I've looked at using ancestors, but I don't quite understand it and honestly don't know if that's the way to go. Any ideas? ..fredrik

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  • Python utf-8, howto align printout

    - by Fredrik
    Hi, I have a array containing japanese caracters as well as "normal". How do I align the printout of these? #!/usr/bin/python # coding=utf-8 a1=['??', '???', 'trazan', '??', '????'] a2=['dipsy', 'laa-laa', 'banarne', 'po', 'tinky winky'] for i,j in zip(a1,a2): print i.ljust(12),':',j print '-'*8 for i,j in zip(a1,a2): print i,len(i) print j,len(j) Output: ?? : dipsy ??? : laa-laa trazan : banarne ?? : po ???? : tinky winky -------- ?? 6 dipsy 5 ??? 9 laa-laa 7 trazan 6 banarne 7 ?? 6 po 2 ???? 12 tinky winky 11 thanks, //Fredrik

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  • Redirecting domain (not google apps) to appengine

    - by fredrik
    Hi, I'm building a application that supports different domains. A small CMS that supports different domains. But what I can't figure out is how to redirect other domains that's outside google apps. I have a domain at google apps, that work's perfectly. When I create a cname that points at either my appid.appspot.com or www.appsdomain.com it just goes to google.com. What do I need to do so the other domains point to my appengine application. ..fredrik

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  • Django/Python best practice template_dict

    - by fredrik
    Hi, After just been coding for about 6-9 months. I probably changed my coding style a number of times after reading some code or read best practices. But one thing I haven't yet come a cross is a good why to populate the template_dict. As of now I pass the template_dict across a number of methods (that changes/modifies it) and returns is. The result is that every methods takes template_dict as first argument and the returns it and this in my eyes doesn't seems to be the best solution. An idea is to have a method that handles all the changes. But I'm curios if there's a best practice for this? Or is it "do what you feel like"-type of thing? The 2 things I think is pretty ugly is to send as an argument and return it in all methods. And the just the var name is written xxx number of times in the code :) ..fredrik

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  • Debian, How to convert filesystem from ISO-8859-1 into UTF-8?

    - by Johan
    I have a old pc that is running Debian stable, that is in need of a upgrade. The problem is that it is using latin1 (ISO-8859-1) for everything, and since the rest of the world has moved to UTF-8 I plan to convert this computer as well. And for this question I will focus in on the files that are served with Samba, and some has some latin1 characters in the filenames (like åäö). Now my plan is to move all data of this old computer onto and a brand new one that is running Debian stable (but with UTF-8). Does anybody have a good idea? Thanks Johan Note: later I plan to use iconv to convert the content of some files with something like this: iconv --from-code=ISO-8859-1 --to-code=UTF-8 iso.txt > utf.txt However I don't know of a good way to convert the filesystem it self. Note: Normally I usaly just scp from one computer to the next, but then I end up with latin1 characters in the utf-8 filesystem... Update: Did a small test round with a hand full of files (with funny chars) in the filenames, and that seemed like it could work. convmv -r -f ISO-8859-1 -t UTF-8 * So it was only to execute with the --notest convmv -r -f ISO-8859-1 -t UTF-8 --notest * Nothing more to it.

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  • Datastore performance, my code or the datastore latency

    - by fredrik
    I had for the last month a bit of a problem with a quite basic datastore query. It involves 2 db.Models with one referring to the other with a db.ReferenceProperty. The problem is that according to the admin logs the request takes about 2-4 seconds to complete. I strip it down to a bare form and a list to display the results. The put works fine, but the get accumulates (in my opinion) way to much cpu time. #The get look like this: outputData['items'] = {} labelsData = Label.all() for label in labelsData: labelItem = label.item.name if labelItem not in outputData['items']: outputData['items'][labelItem] = { 'item' : labelItem, 'labels' : [] } outputData['items'][labelItem]['labels'].append(label.text) path = os.path.join(os.path.dirname(__file__), 'index.html') self.response.out.write(template.render(path, outputData)) #And the models: class Item(db.Model): name = db.StringProperty() class Label(db.Model): text = db.StringProperty() lang = db.StringProperty() item = db.ReferenceProperty(Item) I've tried to make it a number of different way ie. instead of ReferenceProperty storing all Label keys in the Item Model as a db.ListProperty. My test data is just 10 rows in Item and 40 in Label. So my questions: Is it a fools errand to try to optimize this since the high cpu usage is due to the problems with the datastore or have I just screwed up somewhere in the code? ..fredrik

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  • ASP.NET Web API Exception Handling

    - by Fredrik N
    When I talk about exceptions in my product team I often talk about two kind of exceptions, business and critical exceptions. Business exceptions are exceptions thrown based on “business rules”, for example if you aren’t allowed to do a purchase. Business exceptions in most case aren’t important to log into a log file, they can directly be shown to the user. An example of a business exception could be "DeniedToPurchaseException”, or some validation exceptions such as “FirstNameIsMissingException” etc. Critical Exceptions are all other kind of exceptions such as the SQL server is down etc. Those kind of exception message need to be logged and should not reach the user, because they can contain information that can be harmful if it reach out to wrong kind of users. I often distinguish business exceptions from critical exceptions by creating a base class called BusinessException, then in my error handling code I catch on the type BusinessException and all other exceptions will be handled as critical exceptions. This blog post will be about different ways to handle exceptions and how Business and Critical Exceptions could be handled. Web API and Exceptions the basics When an exception is thrown in a ApiController a response message will be returned with a status code set to 500 and a response formatted by the formatters based on the “Accept” or “Content-Type” HTTP header, for example JSON or XML. Here is an example:   public IEnumerable<string> Get() { throw new ApplicationException("Error!!!!!"); return new string[] { "value1", "value2" }; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The response message will be: HTTP/1.1 500 Internal Server Error Content-Length: 860 Content-Type: application/json; charset=utf-8 { "ExceptionType":"System.ApplicationException","Message":"Error!!!!!","StackTrace":" at ..."} .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   The stack trace will be returned to the client, this is because of making it easier to debug. Be careful so you don’t leak out some sensitive information to the client. So as long as you are developing your API, this is not harmful. In a production environment it can be better to log exceptions and return a user friendly exception instead of the original exception. There is a specific exception shipped with ASP.NET Web API that will not use the formatters based on the “Accept” or “Content-Type” HTTP header, it is the exception is the HttpResponseException class. Here is an example where the HttpReponseExcetpion is used: // GET api/values [ExceptionHandling] public IEnumerable<string> Get() { throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.InternalServerError)); return new string[] { "value1", "value2" }; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The response will not contain any content, only header information and the status code based on the HttpStatusCode passed as an argument to the HttpResponseMessage. Because the HttpResponsException takes a HttpResponseMessage as an argument, we can give the response a content: public IEnumerable<string> Get() { throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.InternalServerError) { Content = new StringContent("My Error Message"), ReasonPhrase = "Critical Exception" }); return new string[] { "value1", "value2" }; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   The code above will have the following response:   HTTP/1.1 500 Critical Exception Content-Length: 5 Content-Type: text/plain; charset=utf-8 My Error Message .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The Content property of the HttpResponseMessage doesn’t need to be just plain text, it can also be other formats, for example JSON, XML etc. By using the HttpResponseException we can for example catch an exception and throw a user friendly exception instead: public IEnumerable<string> Get() { try { DoSomething(); return new string[] { "value1", "value2" }; } catch (Exception e) { throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.InternalServerError) { Content = new StringContent("An error occurred, please try again or contact the administrator."), ReasonPhrase = "Critical Exception" }); } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   Adding a try catch to every ApiController methods will only end in duplication of code, by using a custom ExceptionFilterAttribute or our own custom ApiController base class we can reduce code duplicationof code and also have a more general exception handler for our ApiControllers . By creating a custom ApiController’s and override the ExecuteAsync method, we can add a try catch around the base.ExecuteAsync method, but I prefer to skip the creation of a own custom ApiController, better to use a solution that require few files to be modified. The ExceptionFilterAttribute has a OnException method that we can override and add our exception handling. Here is an example: using System; using System.Diagnostics; using System.Net; using System.Net.Http; using System.Web.Http; using System.Web.Http.Filters; public class ExceptionHandlingAttribute : ExceptionFilterAttribute { public override void OnException(HttpActionExecutedContext context) { if (context.Exception is BusinessException) { throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.InternalServerError) { Content = new StringContent(context.Exception.Message), ReasonPhrase = "Exception" }); } //Log Critical errors Debug.WriteLine(context.Exception); throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.InternalServerError) { Content = new StringContent("An error occurred, please try again or contact the administrator."), ReasonPhrase = "Critical Exception" }); } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   Note: Something to have in mind is that the ExceptionFilterAttribute will be ignored if the ApiController action method throws a HttpResponseException. The code above will always make sure a HttpResponseExceptions will be returned, it will also make sure the critical exceptions will show a more user friendly message. The OnException method can also be used to log exceptions. By using a ExceptionFilterAttribute the Get() method in the previous example can now look like this: public IEnumerable<string> Get() { DoSomething(); return new string[] { "value1", "value2" }; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } To use the an ExceptionFilterAttribute, we can for example add the ExceptionFilterAttribute to our ApiControllers methods or to the ApiController class definition, or register it globally for all ApiControllers. You can read more about is here. Note: If something goes wrong in the ExceptionFilterAttribute and an exception is thrown that is not of type HttpResponseException, a formatted exception will be thrown with stack trace etc to the client. How about using a custom IHttpActionInvoker? We can create our own IHTTPActionInvoker and add Exception handling to the invoker. The IHttpActionInvoker will be used to invoke the ApiController’s ExecuteAsync method. Here is an example where the default IHttpActionInvoker, ApiControllerActionInvoker, is used to add exception handling: public class MyApiControllerActionInvoker : ApiControllerActionInvoker { public override Task<HttpResponseMessage> InvokeActionAsync(HttpActionContext actionContext, System.Threading.CancellationToken cancellationToken) { var result = base.InvokeActionAsync(actionContext, cancellationToken); if (result.Exception != null && result.Exception.GetBaseException() != null) { var baseException = result.Exception.GetBaseException(); if (baseException is BusinessException) { return Task.Run<HttpResponseMessage>(() => new HttpResponseMessage(HttpStatusCode.InternalServerError) { Content = new StringContent(baseException.Message), ReasonPhrase = "Error" }); } else { //Log critical error Debug.WriteLine(baseException); return Task.Run<HttpResponseMessage>(() => new HttpResponseMessage(HttpStatusCode.InternalServerError) { Content = new StringContent(baseException.Message), ReasonPhrase = "Critical Error" }); } } return result; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } You can register the IHttpActionInvoker with your own IoC to resolve the MyApiContollerActionInvoker, or add it in the Global.asax: GlobalConfiguration.Configuration.Services.Remove(typeof(IHttpActionInvoker), GlobalConfiguration.Configuration.Services.GetActionInvoker()); GlobalConfiguration.Configuration.Services.Add(typeof(IHttpActionInvoker), new MyApiControllerActionInvoker()); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   How about using a Message Handler for Exception Handling? By creating a custom Message Handler, we can handle error after the ApiController and the ExceptionFilterAttribute is invoked and in that way create a global exception handler, BUT, the only thing we can take a look at is the HttpResponseMessage, we can’t add a try catch around the Message Handler’s SendAsync method. The last Message Handler that will be used in the Wep API pipe-line is the HttpControllerDispatcher and this Message Handler is added to the HttpServer in an early stage. The HttpControllerDispatcher will use the IHttpActionInvoker to invoke the ApiController method. The HttpControllerDipatcher has a try catch that will turn ALL exceptions into a HttpResponseMessage, so that is the reason why a try catch around the SendAsync in a custom Message Handler want help us. If we create our own Host for the Wep API we could create our own custom HttpControllerDispatcher and add or exception handler to that class, but that would be little tricky but is possible. We can in a Message Handler take a look at the HttpResponseMessage’s IsSuccessStatusCode property to see if the request has failed and if we throw the HttpResponseException in our ApiControllers, we could use the HttpResponseException and give it a Reason Phrase and use that to identify business exceptions or critical exceptions. I wouldn’t add an exception handler into a Message Handler, instead I should use the ExceptionFilterAttribute and register it globally for all ApiControllers. BUT, now to another interesting issue. What will happen if we have a Message Handler that throws an exception?  Those exceptions will not be catch and handled by the ExceptionFilterAttribute. I found a  bug in my previews blog post about “Log message Request and Response in ASP.NET WebAPI” in the MessageHandler I use to log incoming and outgoing messages. Here is the code from my blog before I fixed the bug:   public abstract class MessageHandler : DelegatingHandler { protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) { var corrId = string.Format("{0}{1}", DateTime.Now.Ticks, Thread.CurrentThread.ManagedThreadId); var requestInfo = string.Format("{0} {1}", request.Method, request.RequestUri); var requestMessage = await request.Content.ReadAsByteArrayAsync(); await IncommingMessageAsync(corrId, requestInfo, requestMessage); var response = await base.SendAsync(request, cancellationToken); var responseMessage = await response.Content.ReadAsByteArrayAsync(); await OutgoingMessageAsync(corrId, requestInfo, responseMessage); return response; } protected abstract Task IncommingMessageAsync(string correlationId, string requestInfo, byte[] message); protected abstract Task OutgoingMessageAsync(string correlationId, string requestInfo, byte[] message); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   If a ApiController throws a HttpResponseException, the Content property of the HttpResponseMessage from the SendAsync will be NULL. So a null reference exception is thrown within the MessageHandler. The yellow screen of death will be returned to the client, and the content is HTML and the Http status code is 500. The bug in the MessageHandler was solved by adding a check against the HttpResponseMessage’s IsSuccessStatusCode property: public abstract class MessageHandler : DelegatingHandler { protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) { var corrId = string.Format("{0}{1}", DateTime.Now.Ticks, Thread.CurrentThread.ManagedThreadId); var requestInfo = string.Format("{0} {1}", request.Method, request.RequestUri); var requestMessage = await request.Content.ReadAsByteArrayAsync(); await IncommingMessageAsync(corrId, requestInfo, requestMessage); var response = await base.SendAsync(request, cancellationToken); byte[] responseMessage; if (response.IsSuccessStatusCode) responseMessage = await response.Content.ReadAsByteArrayAsync(); else responseMessage = Encoding.UTF8.GetBytes(response.ReasonPhrase); await OutgoingMessageAsync(corrId, requestInfo, responseMessage); return response; } protected abstract Task IncommingMessageAsync(string correlationId, string requestInfo, byte[] message); protected abstract Task OutgoingMessageAsync(string correlationId, string requestInfo, byte[] message); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } If we don’t handle the exceptions that can occur in a custom Message Handler, we can have a hard time to find the problem causing the exception. The savior in this case is the Global.asax’s Application_Error: protected void Application_Error() { var exception = Server.GetLastError(); Debug.WriteLine(exception); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } I would recommend you to add the Application_Error to the Global.asax and log all exceptions to make sure all kind of exception is handled. Summary There are different ways we could add Exception Handling to the Wep API, we can use a custom ApiController, ExceptionFilterAttribute, IHttpActionInvoker or Message Handler. The ExceptionFilterAttribute would be a good place to add a global exception handling, require very few modification, just register it globally for all ApiControllers, even the IHttpActionInvoker can be used to minimize the modifications of files. Adding the Application_Error to the global.asax is a good way to catch all unhandled exception that can occur, for example exception thrown in a Message Handler.   If you want to know when I have posted a blog post, you can follow me on twitter @fredrikn

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