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  • Nginx / uWsgi / Django site can handle more traffic with rewrite URL

    - by Ludo
    Hi there. I'm running a Django app, using uWsgi behind Nginx. I've been doing some performance tuning and load testing using ApacheBench and have discovered something unexpected which I wonder if someone could explain for me. In my Nginx config I have a rewrite directive which catches lots of different URL permutations and then forwards them to the canonical URL I wish to use, eg, it traps www.mysite.com/whatever, www.mysite.co.uk/whatever and forwards them all to http://mysite.com/whatever. If I load test against any of the URLs listed with a redirect (ie, NOT the canonical URL which it is eventually forwarded to), it can serve 15000 concurrent connections without breaking a sweat. If I load test against the canonical URL, which the above test I would have expected got forwarded to anyway, it can't handle nearly as much. It will drop about 4000 of the 15000 requests, and can only handle about 9000 reliably. This is the command line I'm using to test: ab -c15000 -n15000 http://www.mysite.com/somepath/ and ab -c15000 -n15000 http://mysite.com/somepath/ I've tried several different types - it makes no different which order I do them in. This doesn't make sense to me - I can understand why the requests involving a redirect may not handle quite so many concurrent connections, but it's happening the other way round. Can anyone explain? I'd really prefer it if the canonical URL was the one which could handle more traffic. I'll post my Nginx config below. Thanks loads for any help! server { server_name www.somesite.com somesite.net www.somesite.net somesite.co.uk www.somesite.co.uk; rewrite ^(.*) http://somesite.com$1 permanent; } server { root /home/django/domains/somesite.com/live/somesite/; server_name somesite.com somesite-live.myserver.somesite.com; access_log /home/django/domains/somesite.com/live/log/nginx.log; location / { uwsgi_pass unix:////tmp/somesite-live.sock; include uwsgi_params; } location /media { try_files $uri $uri/ /index.html; } location /site_media { try_files $uri $uri/ /index.html; } location = /favicon.ico { empty_gif; } }

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  • Is it generally better to compress content on the proxy server or the app server?

    - by Dan
    We're using an F5 for load balancing and SSL proxying. Behind it we're serving up java applications with Tomcat instances. These are fairly small applications - hundreds of concurrent users. I'd like to compress some of the content, and I'm looking for advice on choosing to configure compression on the F5, or on the tomcat instances. Any big factors in the decision, or is it 6-of-one half-dozen of the other?

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  • (Arch)Linux board with dual ethernet

    - by tekknolagi
    I am looking for a Linux board with the following requirements: 2 ethernet ports (helpful, but only 1 required) 2 USB ports SDXC support (for SD/MicroSD) WiFi (25 concurrent users ideally) HDMI or micro HDMI out I don't know of a good way to find boards. I went through and catalogued a bunch in a spreadsheet, though: https://docs.google.com/spreadsheets/d/1ZyWvg1u5jAeCq4ghpQv3fukl78nYO64utfQgzTP1r7w/edit?usp=sharing

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  • System Requirements of a write-heavy applications serving hundreds of requests per second

    - by Rolando Cruz
    NOTE: I am a self-taught PHP developer who has little to none experience managing web and database servers. I am about to write a web-based attendance system for a very large userbase. I expect around 1000 to 1500 users logged-in at the same time making at least 1 request every 10 seconds or so for a span of 30 minutes a day, 3 times a week. So it's more or less 100 requests per second, or at the very worst 1000 requests in a second (average of 16 concurrent requests? But it could be higher given the short timeframe that users will make these requests. crosses fingers to avoid 100 concurrent requests). I expect two types of transactions, a local (not referring to a local network) and a foreign transaction. local transactions basically download userdata in their locality and cache it for 1 - 2 weeks. Attendance equests will probably be two numeric strings only: userid and eventid. foreign transactions are for attendance of those do not belong in the current locality. This will pass in the following data instead: (numeric) locality_id, (string) full_name. Both requests are done in Ajax so no HTML data included, only JSON. Both type of requests expect at the very least a single numeric response from the server. I think there will be a 50-50 split on the frequency of local and foreign transactions, but there's only a few bytes of difference anyways in the sizes of these transactions. As of this moment the userid may only reach 6 digits and eventid are 4 to 5-digit integers too. I expect my users table to have at least 400k rows, and the event table to have as many as 10k rows, a locality table with at least 1500 rows, and my main attendance table to increase by 400k rows (based on the number of users in the users table) a day for 3 days a week (1.2M rows a week). For me, this sounds big. But is this really that big? Or can this be handled by a single server (not sure about the server specs yet since I'll probably avail of a VPS from ServInt or others)? I tried to read on multiple server setups Heatbeat, DRBD, master-slave setups. But I wonder if they're really necessary. the users table will add around 500 1k rows a week. If this can't be handled by a single server, then if I am to choose a MySQL replication topology, what would be the best setup for this case? Sorry, if I sound vague or the question is too wide. I just don't know what to ask or what do you want to know at this point.

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  • How can Rackspace beat DigitalOcean's Pricepoint? [on hold]

    - by Matt Jensen
    I have recently discovered Digital Ocean and I have found it to be a relatively nice experience for small staging servers, and the thought occurred to me, why am I paying $267~ for a server on Rackspace (40GB RAM, 160 GB Drive, 2 vCPUs, 400 Mb/s) when Digital Ocean offers a server for $40 (40 GB RAM, 60GB Drive [storage is not a concern of mine], 2 vCPUs, ?Mb/s)? Does Rackspace offer some kind of obvious advantages in Transfer speed/bandwidth? My applications are small startups that for the immediate future will only have about 200-300 concurrent users at once.

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  • Is anyone using Node.js as an actual web server?

    - by Jeremy
    I am trying to convince myself to pick it up and start developing with it, but I want to know if anyone has expected stability issues or anything of the sort. I understand it isn't "production" quality, like Apache or IIS. I figure for a small site, it should be fine (max of 200 concurrent connections). Should I assume this?

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  • Jenkins: Accessed denied after turning on global security. How to revert?

    - by serverFaulter
    Need help figuring this one out. How can I fix this issue? I think I enabled global security and saw this error immediately. (while accessing localhost:8080 I get the following...) A problem occurred while processing the request. Please check our bug tracker to see if a similar problem has already been reported. If it is already reported, please vote and put a comment on it to let us gauge the impact of the problem. If you think this is a new issue, please file a new issue. When you file an issue, make sure to add the entire stack trace, along with the version of Jenkins and relevant plugins. The users list might be also useful in understanding what has happened. Stack trace hudson.security.AccessDeniedException2: anonymous is missing the Overall/Read permission at hudson.security.ACL.checkPermission(ACL.java:54) at hudson.model.Node.checkPermission(Node.java:418) at jenkins.model.Jenkins.getTarget(Jenkins.java:3658) at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:656) at org.kohsuke.stapler.Stapler.invoke(Stapler.java:858) at org.kohsuke.stapler.Stapler.invoke(Stapler.java:631) at org.kohsuke.stapler.Stapler.service(Stapler.java:225) at javax.servlet.http.HttpServlet.service(HttpServlet.java:848) at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:686) at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1494) at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:96) at hudson.util.PluginServletFilter.doFilter(PluginServletFilter.java:88) at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1482) at hudson.security.csrf.CrumbFilter.doFilter(CrumbFilter.java:48) at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1482) at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:84) at hudson.security.ChainedServletFilter.doFilter(ChainedServletFilter.java:76) at hudson.security.HudsonFilter.doFilter(HudsonFilter.java:164) at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1482) at org.kohsuke.stapler.compression.CompressionFilter.doFilter(CompressionFilter.java:46) at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1482) at hudson.util.CharacterEncodingFilter.doFilter(CharacterEncodingFilter.java:81) at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1474) at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:499) at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:137) at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:533) at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:231) at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1086) at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:428) at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:193) at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1020) at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:135) at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:116) at org.eclipse.jetty.server.Server.handle(Server.java:370) at org.eclipse.jetty.server.AbstractHttpConnection.handleRequest(AbstractHttpConnection.java:489) at org.eclipse.jetty.server.AbstractHttpConnection.headerComplete(AbstractHttpConnection.java:949) at org.eclipse.jetty.server.AbstractHttpConnection$RequestHandler.headerComplete(AbstractHttpConnection.java:1011) at org.eclipse.jetty.http.HttpParser.parseNext(HttpParser.java:644) at org.eclipse.jetty.http.HttpParser.parseAvailable(HttpParser.java:235) at org.eclipse.jetty.server.AsyncHttpConnection.handle(AsyncHttpConnection.java:82) at org.eclipse.jetty.io.nio.SelectChannelEndPoint.handle(SelectChannelEndPoint.java:668) at org.eclipse.jetty.io.nio.SelectChannelEndPoint$1.run(SelectChannelEndPoint.java:52) at winstone.BoundedExecutorService$1.run(BoundedExecutorService.java:77) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:895) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:918) at java.lang.Thread.run(Thread.java:695)

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  • Windows Server 2008 Terminal Server CALs and Remote Desktop

    - by Chalkey
    Recently we have have installed Windows Server 2008 R2 on one of our development boxes at work. We have 10 Client Access Licence's for Microsoft Windows Terminal Server 2008. I'm under the impression that these licences will entitle us to have 10 concurrent connections to Remote Desktop. At the moment we are only allowed two. Can we have a RD connection per CAL? If so - how do we configure this? Thanks!

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  • Amount of RAM for a web-server user.

    - by Janis Peisenieks
    I'm curently hosting my clients web-sites on some vps servers. What I would like to know, how many visitors can use the multiple web sites concurrently, before I need to migrate each of the sites to their seperate servers? So in laymans terms, how much RAM does a web-page user take on average? For example, how many concurrent visitors can I have on my server, running an Apache server, with 512mb RAM?

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  • Linux tools to choose suitable Cisco ASA 5500

    - by linuxcore
    I have a linux webhosting server which affects a high DDOS. I want to use Cisco ASA 5500 Series Adaptive Security Appliances to protect the linux server from this DDOS. I know there are many factors should you know before you choose the suitable hardware firewall like the amount of this DDOS and pps ..etc Please suggest a linux tools to measure those factors and to help me collect the required informations ( pps - amount of DDOS - concurrent connections and other factors ) Regards,

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  • FTP passive mode with limited port range?

    - by Phil Keeling
    I am running FileZilla FTP Server with passive mode enabled, and due to firewall constraints I have to limit the passive mode port range to only 6 ports. My question is how would FileZilla handle any situation where more than 6 concurrent FTP connections are active and want to passively upload a file. Would it queue the connections and prioritise them in a first in, first out manner? I'm not too familiar with FTP so any insight would be appreciated.

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  • What is the best log rotator for Python wsgi applications ?

    - by Low Kian Seong
    I am running a wsgi based application that has concurrent users accessing it. For my logs needs I tried logrotate but found that logrotate is not too friendly to Python applications, so I tried using RotatingFileHandler and even worse found my logs all chopped up and part of it went missing! I am considering ConcurrentRotatingFileHandler, my question is, has anyone out there experienced the same thing and better yet do you have any battle tested solution for Python wsgi, concurrently accessed applications?

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  • How would I recognize the "spoon-feeding problem" on a dynamic webapp server?

    - by Don Spaulding
    The "spoon-feeding problem", as it was recently explained to me, happens when connections to your application server are tied up feeding data across slow network connections to your clients. This makes sense to me and now I understand the importance of putting a highly-concurrent proxy in front of my app servers. My question is, how did the first person to recognize this problem figure it out? What *nix tools and troubleshooting techniques would help me to recognize this problem if I hadn't had it explained to me?

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  • A Versatile Physical Server

    - by Paul
    How does one judge potential memory and processor needs for linux web servers? Specifically, given: A Debian or Ubuntu OS Running a web server (apache2), and A database (MySQL), and A DNS server (bind), and Being used by up to 100 concurrent users, at some points each downloading high-resolution (0.5 to 1 MB) images via a web app. How much should one budget in terms of RAM, type of processor(s), and number of cores? Thanks!

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  • Apache: scope for environmental variables

    - by Anonymous
    While there's documentation available on Apache environmental variables, I can not find answer to one important question. Imagine I use rewrite rules to set environmental variable RewriteRule ... ... [E=something:1] What is the scope of "something" - global Apache server (this means "something" will be available for other request transactions), this request (means that "something" is only valid for THIS http request (and its related processing - but what's about internal redirects and other internal stuff - are they considered as THIS request, or another one?), and may be set differently within another (concurrent) request?

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  • Dynamic JSON Parsing in .NET with JsonValue

    - by Rick Strahl
    So System.Json has been around for a while in Silverlight, but it's relatively new for the desktop .NET framework and now moving into the lime-light with the pending release of ASP.NET Web API which is bringing a ton of attention to server side JSON usage. The JsonValue, JsonObject and JsonArray objects are going to be pretty useful for Web API applications as they allow you dynamically create and parse JSON values without explicit .NET types to serialize from or into. But even more so I think JsonValue et al. are going to be very useful when consuming JSON APIs from various services. Yes I know C# is strongly typed, why in the world would you want to use dynamic values? So many times I've needed to retrieve a small morsel of information from a large service JSON response and rather than having to map the entire type structure of what that service returns, JsonValue actually allows me to cherry pick and only work with the values I'm interested in, without having to explicitly create everything up front. With JavaScriptSerializer or DataContractJsonSerializer you always need to have a strong type to de-serialize JSON data into. Wouldn't it be nice if no explicit type was required and you could just parse the JSON directly using a very easy to use object syntax? That's exactly what JsonValue, JsonObject and JsonArray accomplish using a JSON parser and some sweet use of dynamic sauce to make it easy to access in code. Creating JSON on the fly with JsonValue Let's start with creating JSON on the fly. It's super easy to create a dynamic object structure. JsonValue uses the dynamic  keyword extensively to make it intuitive to create object structures and turn them into JSON via dynamic object syntax. Here's an example of creating a music album structure with child songs using JsonValue:[TestMethod] public void JsonValueOutputTest() { // strong type instance var jsonObject = new JsonObject(); // dynamic expando instance you can add properties to dynamic album = jsonObject; album.AlbumName = "Dirty Deeds Done Dirt Cheap"; album.Artist = "AC/DC"; album.YearReleased = 1977; album.Songs = new JsonArray() as dynamic; dynamic song = new JsonObject(); song.SongName = "Dirty Deeds Done Dirt Cheap"; song.SongLength = "4:11"; album.Songs.Add(song); song = new JsonObject(); song.SongName = "Love at First Feel"; song.SongLength = "3:10"; album.Songs.Add(song); Console.WriteLine(album.ToString()); } This produces proper JSON just as you would expect: {"AlbumName":"Dirty Deeds Done Dirt Cheap","Artist":"AC\/DC","YearReleased":1977,"Songs":[{"SongName":"Dirty Deeds Done Dirt Cheap","SongLength":"4:11"},{"SongName":"Love at First Feel","SongLength":"3:10"}]} The important thing about this code is that there's no explicitly type that is used for holding the values to serialize to JSON. I am essentially creating this value structure on the fly by adding properties and then serialize it to JSON. This means this code can be entirely driven at runtime without compile time restraints of structure for the JSON output. Here I use JsonObject() to create a new object and immediately cast it to dynamic. JsonObject() is kind of similar in behavior to ExpandoObject in that it allows you to add properties by simply assigning to them. Internally, JsonValue/JsonObject these values are stored in pseudo collections of key value pairs that are exposed as properties through the DynamicObject functionality in .NET. The syntax gets a little tedious only if you need to create child objects or arrays that have to be explicitly defined first. Other than that the syntax looks like normal object access sytnax. Always remember though these values are dynamic - which means no Intellisense and no compiler type checking. It's up to you to ensure that the values you create are accessed consistently and without typos in your code. Note that you can also access the JsonValue instance directly and get access to the underlying type. This means you can assign properties by string, which can be useful for fully data driven JSON generation from other structures. Below you can see both styles of access next to each other:// strong type instance var jsonObject = new JsonObject(); // you can explicitly add values here jsonObject.Add("Entered", DateTime.Now); // expando style instance you can just 'use' properties dynamic album = jsonObject; album.AlbumName = "Dirty Deeds Done Dirt Cheap"; JsonValue internally stores properties keys and values in collections and you can iterate over them at runtime. You can also manipulate the collections if you need to to get the object structure to look exactly like you want. Again, if you've used ExpandoObject before JsonObject/Value are very similar in the behavior of the structure. Reading JSON strings into JsonValue The JsonValue structure supports importing JSON via the Parse() and Load() methods which can read JSON data from a string or various streams respectively. Essentially JsonValue includes the core JSON parsing to turn a JSON string into a collection of JsonValue objects that can be then referenced using familiar dynamic object syntax. Here's a simple example:[TestMethod] public void JsonValueParsingTest() { var jsonString = @"{""Name"":""Rick"",""Company"":""West Wind"",""Entered"":""2012-03-16T00:03:33.245-10:00""}"; dynamic json = JsonValue.Parse(jsonString); // values require casting string name = json.Name; string company = json.Company; DateTime entered = json.Entered; Assert.AreEqual(name, "Rick"); Assert.AreEqual(company, "West Wind"); } The JSON string represents an object with three properties which is parsed into a JsonValue object and cast to dynamic. Once cast to dynamic I can then go ahead and access the object using familiar object syntax. Note that the actual values - json.Name, json.Company, json.Entered - are actually of type JsonPrimitive and I have to assign them to their appropriate types first before I can do type comparisons. The dynamic properties will automatically cast to the right type expected as long as the compiler can resolve the type of the assignment or usage. The AreEqual() method oesn't as it expects two object instances and comparing json.Company to "West Wind" is comparing two different types (JsonPrimitive to String) which fails. So the intermediary assignment is required to make the test pass. The JSON structure can be much more complex than this simple example. Here's another example of an array of albums serialized to JSON and then parsed through with JsonValue():[TestMethod] public void JsonArrayParsingTest() { var jsonString = @"[ { ""Id"": ""b3ec4e5c"", ""AlbumName"": ""Dirty Deeds Done Dirt Cheap"", ""Artist"": ""AC/DC"", ""YearReleased"": 1977, ""Entered"": ""2012-03-16T00:13:12.2810521-10:00"", ""AlbumImageUrl"": ""http://ecx.images-amazon.com/images/I/61kTaH-uZBL._AA115_.jpg"", ""AmazonUrl"": ""http://www.amazon.com/gp/product/B00008BXJ4/ref=as_li_ss_tl?ie=UTF8&tag=westwindtechn-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=B00008BXJ4"", ""Songs"": [ { ""AlbumId"": ""b3ec4e5c"", ""SongName"": ""Dirty Deeds Done Dirt Cheap"", ""SongLength"": ""4:11"" }, { ""AlbumId"": ""b3ec4e5c"", ""SongName"": ""Love at First Feel"", ""SongLength"": ""3:10"" }, { ""AlbumId"": ""b3ec4e5c"", ""SongName"": ""Big Balls"", ""SongLength"": ""2:38"" } ] }, { ""Id"": ""67280fb8"", ""AlbumName"": ""Echoes, Silence, Patience & Grace"", ""Artist"": ""Foo Fighters"", ""YearReleased"": 2007, ""Entered"": ""2012-03-16T00:13:12.2810521-10:00"", ""AlbumImageUrl"": ""http://ecx.images-amazon.com/images/I/41mtlesQPVL._SL500_AA280_.jpg"", ""AmazonUrl"": ""http://www.amazon.com/gp/product/B000UFAURI/ref=as_li_ss_tl?ie=UTF8&tag=westwindtechn-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=B000UFAURI"", ""Songs"": [ { ""AlbumId"": ""67280fb8"", ""SongName"": ""The Pretender"", ""SongLength"": ""4:29"" }, { ""AlbumId"": ""67280fb8"", ""SongName"": ""Let it Die"", ""SongLength"": ""4:05"" }, { ""AlbumId"": ""67280fb8"", ""SongName"": ""Erase/Replay"", ""SongLength"": ""4:13"" } ] }, { ""Id"": ""7b919432"", ""AlbumName"": ""End of the Silence"", ""Artist"": ""Henry Rollins Band"", ""YearReleased"": 1992, ""Entered"": ""2012-03-16T00:13:12.2800521-10:00"", ""AlbumImageUrl"": ""http://ecx.images-amazon.com/images/I/51FO3rb1tuL._SL160_AA160_.jpg"", ""AmazonUrl"": ""http://www.amazon.com/End-Silence-Rollins-Band/dp/B0000040OX/ref=sr_1_5?ie=UTF8&qid=1302232195&sr=8-5"", ""Songs"": [ { ""AlbumId"": ""7b919432"", ""SongName"": ""Low Self Opinion"", ""SongLength"": ""5:24"" }, { ""AlbumId"": ""7b919432"", ""SongName"": ""Grip"", ""SongLength"": ""4:51"" } ] } ]"; dynamic albums = JsonValue.Parse(jsonString); foreach (dynamic album in albums) { Console.WriteLine(album.AlbumName + " (" + album.YearReleased.ToString() + ")"); foreach (dynamic song in album.Songs) { Console.WriteLine("\t" + song.SongName ); } } Console.WriteLine(albums[0].AlbumName); Console.WriteLine(albums[0].Songs[1].SongName);}   It's pretty sweet how easy it becomes to parse even complex JSON and then just run through the object using object syntax, yet without an explicit type in the mix. In fact it looks and feels a lot like if you were using JavaScript to parse through this data, doesn't it? And that's the point…© Rick Strahl, West Wind Technologies, 2005-2012Posted in .NET  Web Api  JSON   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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  • Using LINQ Distinct: With an Example on ASP.NET MVC SelectListItem

    - by Joe Mayo
    One of the things that might be surprising in the LINQ Distinct standard query operator is that it doesn’t automatically work properly on custom classes. There are reasons for this, which I’ll explain shortly. The example I’ll use in this post focuses on pulling a unique list of names to load into a drop-down list. I’ll explain the sample application, show you typical first shot at Distinct, explain why it won’t work as you expect, and then demonstrate a solution to make Distinct work with any custom class. The technologies I’m using are  LINQ to Twitter, LINQ to Objects, Telerik Extensions for ASP.NET MVC, ASP.NET MVC 2, and Visual Studio 2010. The function of the example program is to show a list of people that I follow.  In Twitter API vernacular, these people are called “Friends”; though I’ve never met most of them in real life. This is part of the ubiquitous language of social networking, and Twitter in particular, so you’ll see my objects named accordingly. Where Distinct comes into play is because I want to have a drop-down list with the names of the friends appearing in the list. Some friends are quite verbose, which means I can’t just extract names from each tweet and populate the drop-down; otherwise, I would end up with many duplicate names. Therefore, Distinct is the appropriate operator to eliminate the extra entries from my friends who tend to be enthusiastic tweeters. The sample doesn’t do anything with the drop-down list and I leave that up to imagination for what it’s practical purpose could be; perhaps a filter for the list if I only want to see a certain person’s tweets or maybe a quick list that I plan to combine with a TextBox and Button to reply to a friend. When the program runs, you’ll need to authenticate with Twitter, because I’m using OAuth (DotNetOpenAuth), for authentication, and then you’ll see the drop-down list of names above the grid with the most recent tweets from friends. Here’s what the application looks like when it runs: As you can see, there is a drop-down list above the grid. The drop-down list is where most of the focus of this article will be. There is some description of the code before we talk about the Distinct operator, but we’ll get there soon. This is an ASP.NET MVC2 application, written with VS 2010. Here’s the View that produces this screen: <%@ Page Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage<TwitterFriendsViewModel>" %> <%@ Import Namespace="DistinctSelectList.Models" %> <asp:Content ID="Content1" ContentPlaceHolderID="TitleContent" runat="server">     Home Page </asp:Content><asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">     <fieldset>         <legend>Twitter Friends</legend>         <div>             <%= Html.DropDownListFor(                     twendVM => twendVM.FriendNames,                     Model.FriendNames,                     "<All Friends>") %>         </div>         <div>             <% Html.Telerik().Grid<TweetViewModel>(Model.Tweets)                    .Name("TwitterFriendsGrid")                    .Columns(cols =>                     {                         cols.Template(col =>                             { %>                                 <img src="<%= col.ImageUrl %>"                                      alt="<%= col.ScreenName %>" />                         <% });                         cols.Bound(col => col.ScreenName);                         cols.Bound(col => col.Tweet);                     })                    .Render(); %>         </div>     </fieldset> </asp:Content> As shown above, the Grid is from Telerik’s Extensions for ASP.NET MVC. The first column is a template that renders the user’s Avatar from a URL provided by the Twitter query. Both the Grid and DropDownListFor display properties that are collections from a TwitterFriendsViewModel class, shown below: using System.Collections.Generic; using System.Web.Mvc; namespace DistinctSelectList.Models { /// /// For finding friend info on screen /// public class TwitterFriendsViewModel { /// /// Display names of friends in drop-down list /// public List FriendNames { get; set; } /// /// Display tweets in grid /// public List Tweets { get; set; } } } I created the TwitterFreindsViewModel. The two Lists are what the View consumes to populate the DropDownListFor and Grid. Notice that FriendNames is a List of SelectListItem, which is an MVC class. Another custom class I created is the TweetViewModel (the type of the Tweets List), shown below: namespace DistinctSelectList.Models { /// /// Info on friend tweets /// public class TweetViewModel { /// /// User's avatar /// public string ImageUrl { get; set; } /// /// User's Twitter name /// public string ScreenName { get; set; } /// /// Text containing user's tweet /// public string Tweet { get; set; } } } The initial Twitter query returns much more information than we need for our purposes and this a special class for displaying info in the View.  Now you know about the View and how it’s constructed. Let’s look at the controller next. The controller for this demo performs authentication, data retrieval, data manipulation, and view selection. I’ll skip the description of the authentication because it’s a normal part of using OAuth with LINQ to Twitter. Instead, we’ll drill down and focus on the Distinct operator. However, I’ll show you the entire controller, below,  so that you can see how it all fits together: using System.Linq; using System.Web.Mvc; using DistinctSelectList.Models; using LinqToTwitter; namespace DistinctSelectList.Controllers { [HandleError] public class HomeController : Controller { private MvcOAuthAuthorization auth; private TwitterContext twitterCtx; /// /// Display a list of friends current tweets /// /// public ActionResult Index() { auth = new MvcOAuthAuthorization(InMemoryTokenManager.Instance, InMemoryTokenManager.AccessToken); string accessToken = auth.CompleteAuthorize(); if (accessToken != null) { InMemoryTokenManager.AccessToken = accessToken; } if (auth.CachedCredentialsAvailable) { auth.SignOn(); } else { return auth.BeginAuthorize(); } twitterCtx = new TwitterContext(auth); var friendTweets = (from tweet in twitterCtx.Status where tweet.Type == StatusType.Friends select new TweetViewModel { ImageUrl = tweet.User.ProfileImageUrl, ScreenName = tweet.User.Identifier.ScreenName, Tweet = tweet.Text }) .ToList(); var friendNames = (from tweet in friendTweets select new SelectListItem { Text = tweet.ScreenName, Value = tweet.ScreenName }) .Distinct() .ToList(); var twendsVM = new TwitterFriendsViewModel { Tweets = friendTweets, FriendNames = friendNames }; return View(twendsVM); } public ActionResult About() { return View(); } } } The important part of the listing above are the LINQ to Twitter queries for friendTweets and friendNames. Both of these results are used in the subsequent population of the twendsVM instance that is passed to the view. Let’s dissect these two statements for clarification and focus on what is happening with Distinct. The query for friendTweets gets a list of the 20 most recent tweets (as specified by the Twitter API for friend queries) and performs a projection into the custom TweetViewModel class, repeated below for your convenience: var friendTweets = (from tweet in twitterCtx.Status where tweet.Type == StatusType.Friends select new TweetViewModel { ImageUrl = tweet.User.ProfileImageUrl, ScreenName = tweet.User.Identifier.ScreenName, Tweet = tweet.Text }) .ToList(); The LINQ to Twitter query above simplifies what we need to work with in the View and the reduces the amount of information we have to look at in subsequent queries. Given the friendTweets above, the next query performs another projection into an MVC SelectListItem, which is required for binding to the DropDownList.  This brings us to the focus of this blog post, writing a correct query that uses the Distinct operator. The query below uses LINQ to Objects, querying the friendTweets collection to get friendNames: var friendNames = (from tweet in friendTweets select new SelectListItem { Text = tweet.ScreenName, Value = tweet.ScreenName }) .Distinct() .ToList(); The above implementation of Distinct seems normal, but it is deceptively incorrect. After running the query above, by executing the application, you’ll notice that the drop-down list contains many duplicates.  This will send you back to the code scratching your head, but there’s a reason why this happens. To understand the problem, we must examine how Distinct works in LINQ to Objects. Distinct has two overloads: one without parameters, as shown above, and another that takes a parameter of type IEqualityComparer<T>.  In the case above, no parameters, Distinct will call EqualityComparer<T>.Default behind the scenes to make comparisons as it iterates through the list. You don’t have problems with the built-in types, such as string, int, DateTime, etc, because they all implement IEquatable<T>. However, many .NET Framework classes, such as SelectListItem, don’t implement IEquatable<T>. So, what happens is that EqualityComparer<T>.Default results in a call to Object.Equals, which performs reference equality on reference type objects.  You don’t have this problem with value types because the default implementation of Object.Equals is bitwise equality. However, most of your projections that use Distinct are on classes, just like the SelectListItem used in this demo application. So, the reason why Distinct didn’t produce the results we wanted was because we used a type that doesn’t define its own equality and Distinct used the default reference equality. This resulted in all objects being included in the results because they are all separate instances in memory with unique references. As you might have guessed, the solution to the problem is to use the second overload of Distinct that accepts an IEqualityComparer<T> instance. If you were projecting into your own custom type, you could make that type implement IEqualityComparer<T>, but SelectListItem belongs to the .NET Framework Class Library.  Therefore, the solution is to create a custom type to implement IEqualityComparer<T>, as in the SelectListItemComparer class, shown below: using System.Collections.Generic; using System.Web.Mvc; namespace DistinctSelectList.Models { public class SelectListItemComparer : EqualityComparer { public override bool Equals(SelectListItem x, SelectListItem y) { return x.Value.Equals(y.Value); } public override int GetHashCode(SelectListItem obj) { return obj.Value.GetHashCode(); } } } The SelectListItemComparer class above doesn’t implement IEqualityComparer<SelectListItem>, but rather derives from EqualityComparer<SelectListItem>. Microsoft recommends this approach for consistency with the behavior of generic collection classes. However, if your custom type already derives from a base class, go ahead and implement IEqualityComparer<T>, which will still work. EqualityComparer is an abstract class, that implements IEqualityComparer<T> with Equals and GetHashCode abstract methods. For the purposes of this application, the SelectListItem.Value property is sufficient to determine if two items are equal.   Since SelectListItem.Value is type string, the code delegates equality to the string class. The code also delegates the GetHashCode operation to the string class.You might have other criteria in your own object and would need to define what it means for your object to be equal. Now that we have an IEqualityComparer<SelectListItem>, let’s fix the problem. The code below modifies the query where we want distinct values: var friendNames = (from tweet in friendTweets select new SelectListItem { Text = tweet.ScreenName, Value = tweet.ScreenName }) .Distinct(new SelectListItemComparer()) .ToList(); Notice how the code above passes a new instance of SelectListItemComparer as the parameter to the Distinct operator. Now, when you run the application, the drop-down list will behave as you expect, showing only a unique set of names. In addition to Distinct, other LINQ Standard Query Operators have overloads that accept IEqualityComparer<T>’s, You can use the same techniques as shown here, with SelectListItemComparer, with those other operators as well. Now you know how to resolve problems with getting Distinct to work properly and also have a way to fix problems with other operators that require equality comparisons. @JoeMayo

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  • C#/.NET Little Wonders: Use Cast() and TypeOf() to Change Sequence Type

    - by James Michael Hare
    Once again, in this series of posts I look at the parts of the .NET Framework that may seem trivial, but can help improve your code by making it easier to write and maintain. The index of all my past little wonders posts can be found here. We’ve seen how the Select() extension method lets you project a sequence from one type to a new type which is handy for getting just parts of items, or building new items.  But what happens when the items in the sequence are already the type you want, but the sequence itself is typed to an interface or super-type instead of the sub-type you need? For example, you may have a sequence of Rectangle stored in an IEnumerable<Shape> and want to consider it an IEnumerable<Rectangle> sequence instead.  Today we’ll look at two handy extension methods, Cast<TResult>() and OfType<TResult>() which help you with this task. Cast<TResult>() – Attempt to cast all items to type TResult So, the first thing we can do would be to attempt to create a sequence of TResult from every item in the source sequence.  Typically we’d do this if we had an IEnumerable<T> where we knew that every item was actually a TResult where TResult inherits/implements T. For example, assume the typical Shape example classes: 1: // abstract base class 2: public abstract class Shape { } 3:  4: // a basic rectangle 5: public class Rectangle : Shape 6: { 7: public int Widtgh { get; set; } 8: public int Height { get; set; } 9: } And let’s assume we have a sequence of Shape where every Shape is a Rectangle… 1: var shapes = new List<Shape> 2: { 3: new Rectangle { Width = 3, Height = 5 }, 4: new Rectangle { Width = 10, Height = 13 }, 5: // ... 6: }; To get the sequence of Shape as a sequence of Rectangle, of course, we could use a Select() clause, such as: 1: // select each Shape, cast it to Rectangle 2: var rectangles = shapes 3: .Select(s => (Rectangle)s) 4: .ToList(); But that’s a bit verbose, and fortunately there is already a facility built in and ready to use in the form of the Cast<TResult>() extension method: 1: // cast each item to Rectangle and store in a List<Rectangle> 2: var rectangles = shapes 3: .Cast<Rectangle>() 4: .ToList(); However, we should note that if anything in the list cannot be cast to a Rectangle, you will get an InvalidCastException thrown at runtime.  Thus, if our Shape sequence had a Circle in it, the call to Cast<Rectangle>() would have failed.  As such, you should only do this when you are reasonably sure of what the sequence actually contains (or are willing to handle an exception if you’re wrong). Another handy use of Cast<TResult>() is using it to convert an IEnumerable to an IEnumerable<T>.  If you look at the signature, you’ll see that the Cast<TResult>() extension method actually extends the older, object-based IEnumerable interface instead of the newer, generic IEnumerable<T>.  This is your gateway method for being able to use LINQ on older, non-generic sequences.  For example, consider the following: 1: // the older, non-generic collections are sequence of object 2: var shapes = new ArrayList 3: { 4: new Rectangle { Width = 3, Height = 13 }, 5: new Rectangle { Width = 10, Height = 20 }, 6: // ... 7: }; Since this is an older, object based collection, we cannot use the LINQ extension methods on it directly.  For example, if I wanted to query the Shape sequence for only those Rectangles whose Width is > 5, I can’t do this: 1: // compiler error, Where() operates on IEnumerable<T>, not IEnumerable 2: var bigRectangles = shapes.Where(r => r.Width > 5); However, I can use Cast<Rectangle>() to treat my ArrayList as an IEnumerable<Rectangle> and then do the query! 1: // ah, that’s better! 2: var bigRectangles = shapes.Cast<Rectangle>().Where(r => r.Width > 5); Or, if you prefer, in LINQ query expression syntax: 1: var bigRectangles = from s in shapes.Cast<Rectangle>() 2: where s.Width > 5 3: select s; One quick warning: Cast<TResult>() only attempts to cast, it won’t perform a cast conversion.  That is, consider this: 1: var intList = new List<int> { 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89 }; 2:  3: // casting ints to longs, this should work, right? 4: var asLong = intList.Cast<long>().ToList(); Will the code above work?  No, you’ll get a InvalidCastException. Remember that Cast<TResult>() is an extension of IEnumerable, thus it is a sequence of object, which means that it will box every int as an object as it enumerates over it, and there is no cast conversion from object to long, and thus the cast fails.  In other words, a cast from int to long will succeed because there is a conversion from int to long.  But a cast from int to object to long will not, because you can only unbox an item by casting it to its exact type. For more information on why cast-converting boxed values doesn’t work, see this post on The Dangers of Casting Boxed Values (here). OfType<TResult>() – Filter sequence to only items of type TResult So, we’ve seen how we can use Cast<TResult>() to change the type of our sequence, when we expect all the items of the sequence to be of a specific type.  But what do we do when a sequence contains many different types, and we are only concerned with a subset of a given type? For example, what if a sequence of Shape contains Rectangle and Circle instances, and we just want to select all of the Rectangle instances?  Well, let’s say we had this sequence of Shape: 1: var shapes = new List<Shape> 2: { 3: new Rectangle { Width = 3, Height = 5 }, 4: new Rectangle { Width = 10, Height = 13 }, 5: new Circle { Radius = 10 }, 6: new Square { Side = 13 }, 7: // ... 8: }; Well, we could get the rectangles using Select(), like: 1: var onlyRectangles = shapes.Where(s => s is Rectangle).ToList(); But fortunately, an easier way has already been written for us in the form of the OfType<T>() extension method: 1: // returns only a sequence of the shapes that are Rectangles 2: var onlyRectangles = shapes.OfType<Rectangle>().ToList(); Now we have a sequence of only the Rectangles in the original sequence, we can also use this to chain other queries that depend on Rectangles, such as: 1: // select only Rectangles, then filter to only those more than 2: // 5 units wide... 3: var onlyBigRectangles = shapes.OfType<Rectangle>() 4: .Where(r => r.Width > 5) 5: .ToList(); The OfType<Rectangle>() will filter the sequence to only the items that are of type Rectangle (or a subclass of it), and that results in an IEnumerable<Rectangle>, we can then apply the other LINQ extension methods to query that list further. Just as Cast<TResult>() is an extension method on IEnumerable (and not IEnumerable<T>), the same is true for OfType<T>().  This means that you can use OfType<TResult>() on object-based collections as well. For example, given an ArrayList containing Shapes, as below: 1: // object-based collections are a sequence of object 2: var shapes = new ArrayList 3: { 4: new Rectangle { Width = 3, Height = 5 }, 5: new Rectangle { Width = 10, Height = 13 }, 6: new Circle { Radius = 10 }, 7: new Square { Side = 13 }, 8: // ... 9: }; We can use OfType<Rectangle> to filter the sequence to only Rectangle items (and subclasses), and then chain other LINQ expressions, since we will then be of type IEnumerable<Rectangle>: 1: // OfType() converts the sequence of object to a new sequence 2: // containing only Rectangle or sub-types of Rectangle. 3: var onlyBigRectangles = shapes.OfType<Rectangle>() 4: .Where(r => r.Width > 5) 5: .ToList(); Summary So now we’ve seen two different ways to get a sequence of a superclass or interface down to a more specific sequence of a subclass or implementation.  The Cast<TResult>() method casts every item in the source sequence to type TResult, and the OfType<TResult>() method selects only those items in the source sequence that are of type TResult. You can use these to downcast sequences, or adapt older types and sequences that only implement IEnumerable (such as DataTable, ArrayList, etc.). Technorati Tags: C#,CSharp,.NET,LINQ,Little Wonders,TypeOf,Cast,IEnumerable<T>

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  • Automatically create bug resolution task using the TFS 2010 API

    - by Bob Hardister
    My customer requires bug resolution to be approved and tracked.  To minimize the overhead for developers I implemented a TFS 2010 server-side plug-in to automatically create a child resolution task for the bug when the “CCB” field is set to approved. The CCB field is a custom field.  I also added the story points field to the bug WIT for sizing purposes. Redundant tasks will not be created unless the bug title is changed or the prior task is closed. The program writes an audit trail to a log file visible in the TFS Admin Console Log view. Here’s the code. BugAutoTask.cs /* SPECIFICATION * When the CCB field on the bug is set to approved, create a child task where the task: * name = Resolve bug [ID] - [Title of bug] * assigned to = same as assigned to field on the bug * same area path * same iteration path * activity = Bug Resolution * original estimate = bug points * * The source code is used to build a dll (Ows.TeamFoundation.BugAutoTaskCreation.PlugIns.dll), * which needs to be copied to * C:\Program Files\Microsoft Team Foundation Server 2010\Application Tier\Web Services\bin\Plugins * on ALL TFS application-tier servers. * * Author: Bob Hardister. */ using System; using System.Collections.Generic; using System.IO; using System.Xml; using System.Text; using System.Diagnostics; using System.Linq; using Microsoft.TeamFoundation.Common; using Microsoft.TeamFoundation.Framework.Server; using Microsoft.TeamFoundation.WorkItemTracking.Client; using Microsoft.TeamFoundation.WorkItemTracking.Server; using Microsoft.TeamFoundation.Client; using System.Collections; namespace BugAutoTaskCreation { public class BugAutoTask : ISubscriber { public EventNotificationStatus ProcessEvent(TeamFoundationRequestContext requestContext, NotificationType notificationType, object notificationEventArgs, out int statusCode, out string statusMessage, out ExceptionPropertyCollection properties) { statusCode = 0; properties = null; statusMessage = String.Empty; // Error message for for tracing last code executed and optional fields string lastStep = "No field values found or set "; try { if ((notificationType == NotificationType.Notification) && (notificationEventArgs.GetType() == typeof(WorkItemChangedEvent))) { WorkItemChangedEvent workItemChange = (WorkItemChangedEvent)notificationEventArgs; // see ConnectToTFS() method below to select which TFS instance/collection // to connect to TfsTeamProjectCollection tfs = ConnectToTFS(); WorkItemStore wiStore = tfs.GetService<WorkItemStore>(); lastStep = lastStep + ": connection to TFS successful "; // Get the work item that was just changed by the user. WorkItem witem = wiStore.GetWorkItem(workItemChange.CoreFields.IntegerFields[0].NewValue); lastStep = lastStep + ": retrieved changed work item, ID:" + witem.Id + " "; // Filter for Bug work items only if (witem.Type.Name == "Bug") { // DEBUG lastStep = lastStep + ": changed work item is a bug "; // Filter for CCB (i.e. Baseline Status) field set to approved only bool BaselineStatusChange = false; if (workItemChange.ChangedFields != null) { ProcessBugRevision(ref lastStep, workItemChange, wiStore, ref witem, ref BaselineStatusChange); } } } } catch (Exception e) { Trace.WriteLine(e.Message); Logger log = new Logger(); log.WriteLineToLog(MsgLevel.Error, "Application error: " + lastStep + " - " + e.Message + " - " + e.InnerException); } statusCode = 1; statusMessage = "Bug Auto Task Evaluation Completed"; properties = null; return EventNotificationStatus.ActionApproved; } // PRIVATE METHODS private static void ProcessBugRevision(ref string lastStep, WorkItemChangedEvent workItemChange, WorkItemStore wiStore, ref WorkItem witem, ref bool BaselineStatusChange) { foreach (StringField field in workItemChange.ChangedFields.StringFields) { // DEBUG lastStep = lastStep + ": last changed field is - " + field.Name + " "; if (field.Name == "Baseline Status") { lastStep = lastStep + ": retrieved bug baseline status field value, bug ID:" + witem.Id + " "; BaselineStatusChange = (field.NewValue != field.OldValue); if ((BaselineStatusChange) && (field.NewValue == "Approved")) { // Instanciate logger Logger log = new Logger(); // *** Create resolution task for this bug *** // ******************************************* // Get the team project and selected field values of the bug work item Project teamProject = witem.Project; int bugID = witem.Id; string bugTitle = witem.Fields["System.Title"].Value.ToString(); string bugAssignedTo = witem.Fields["System.AssignedTo"].Value.ToString(); string bugAreaPath = witem.Fields["System.AreaPath"].Value.ToString(); string bugIterationPath = witem.Fields["System.IterationPath"].Value.ToString(); string bugChangedBy = witem.Fields["System.ChangedBy"].OriginalValue.ToString(); string bugTeamProject = witem.Project.Name; lastStep = lastStep + ": all mandatory bug field values found "; // Optional fields Field bugPoints = witem.Fields["Microsoft.VSTS.Scheduling.StoryPoints"]; if (bugPoints.Value != null) { lastStep = lastStep + ": all mandatory and optional bug field values found "; } // Initialize child resolution task title string childTaskTitle = "Resolve bug " + bugID + " - " + bugTitle; // At this point I can check if a resolution task (of the same name) // for the bug already exist // If so, do not create a new resolution task bool createResolutionTask = true; WorkItem parentBug = wiStore.GetWorkItem(bugID); WorkItemLinkCollection links = parentBug.WorkItemLinks; foreach (WorkItemLink wil in links) { if (wil.LinkTypeEnd.Name == "Child") { WorkItem childTask = wiStore.GetWorkItem(wil.TargetId); if ((childTask.Title == childTaskTitle) && (childTask.State != "Closed")) { createResolutionTask = false; log.WriteLineToLog(MsgLevel.Info, "Team project " + bugTeamProject + ": " + bugChangedBy + " - set the CCB field to \"Approved\" for bug, ID: " + bugID + ". Task not created as open one of the same name already exist, ID:" + childTask.Id); } } } if (createResolutionTask) { // Define the work item type of the new work item WorkItemTypeCollection workItemTypes = wiStore.Projects[teamProject.Name].WorkItemTypes; WorkItemType wiType = workItemTypes["Task"]; // Setup the new task and assign field values witem = new WorkItem(wiType); witem.Fields["System.Title"].Value = "Resolve bug " + bugID + " - " + bugTitle; witem.Fields["System.AssignedTo"].Value = bugAssignedTo; witem.Fields["System.AreaPath"].Value = bugAreaPath; witem.Fields["System.IterationPath"].Value = bugIterationPath; witem.Fields["Microsoft.VSTS.Common.Activity"].Value = "Bug Resolution"; lastStep = lastStep + ": all mandatory task field values set "; // Optional fields if (bugPoints.Value != null) { witem.Fields["Microsoft.VSTS.Scheduling.OriginalEstimate"].Value = bugPoints.Value; lastStep = lastStep + ": all mandatory and optional task field values set "; } // Check for validation errors before saving the new task and linking it to the bug ArrayList validationErrors = witem.Validate(); if (validationErrors.Count == 0) { witem.Save(); // Link the new task (child) to the bug (parent) var linkType = wiStore.WorkItemLinkTypes[CoreLinkTypeReferenceNames.Hierarchy]; // Fetch the work items to be linked var parentWorkItem = wiStore.GetWorkItem(bugID); int taskID = witem.Id; var childWorkItem = wiStore.GetWorkItem(taskID); // Add a new link to the parent relating the child and save it parentWorkItem.Links.Add(new WorkItemLink(linkType.ForwardEnd, childWorkItem.Id)); parentWorkItem.Save(); log.WriteLineToLog(MsgLevel.Info, "Team project " + bugTeamProject + ": " + bugChangedBy + " - set the CCB field to \"Approved\" for bug, ID:" + bugID + ", which automatically created child resolution task, ID:" + taskID); } else { log.WriteLineToLog(MsgLevel.Error, "Error in creating bug resolution child task for bug ID:" + bugID); foreach (Field taskField in validationErrors) { log.WriteLineToLog(MsgLevel.Error, " - Validation Error in task field: " + taskField.ReferenceName); } } } } } } } private TfsTeamProjectCollection ConnectToTFS() { // Connect to TFS string tfsUri = string.Empty; // Production TFS instance production collection tfsUri = @"xxxx"; // Production TFS instance admin collection //tfsUri = @"xxxxx"; // Local TFS testing instance default collection //tfsUri = @"xxxxx"; TfsTeamProjectCollection tfs = new TfsTeamProjectCollection(new System.Uri(tfsUri)); tfs.EnsureAuthenticated(); return tfs; } // HELPERS public string Name { get { return "Bug Auto Task Creation Event Handler"; } } public SubscriberPriority Priority { get { return SubscriberPriority.Normal; } } public enum MsgLevel { Info, Warning, Error }; public Type[] SubscribedTypes() { return new Type[1] { typeof(WorkItemChangedEvent) }; } } } Logger.cs using System; using System.Collections.Generic; using System.IO; using System.Linq; using System.Text; using System.Windows.Forms; namespace BugAutoTaskCreation { class Logger { // fields private string _ApplicationDirectory = @"C:\ProgramData\Microsoft\Team Foundation\Server Configuration\Logs"; private string _LogFileName = @"\CFG_ACCT_AT_OWS_BugAutoTaskCreation.log"; private string _LogFile; private string _LogTimestamp = DateTime.Now.ToString("MM/dd/yyyy HH:mm:ss"); private string _MsgLevelText = string.Empty; // default constructor public Logger() { // check for a prior log file FileInfo logFile = new FileInfo(_ApplicationDirectory + _LogFileName); if (!logFile.Exists) { CreateNewLogFile(ref logFile); } } // properties public string ApplicationDirectory { get { return _ApplicationDirectory; } set { _ApplicationDirectory = value; } } public string LogFile { get { _LogFile = _ApplicationDirectory + _LogFileName; return _LogFile; } set { _LogFile = value; } } // PUBLIC METHODS public void WriteLineToLog(BugAutoTask.MsgLevel msgLevel, string logRecord) { try { // set msgLevel text if (msgLevel == BugAutoTask.MsgLevel.Info) { _MsgLevelText = "[Info @" + MsgTimeStamp() + "] "; } else if (msgLevel == BugAutoTask.MsgLevel.Warning) { _MsgLevelText = "[Warning @" + MsgTimeStamp() + "] "; } else if (msgLevel == BugAutoTask.MsgLevel.Error) { _MsgLevelText = "[Error @" + MsgTimeStamp() + "] "; } else { _MsgLevelText = "[Error: unsupported message level @" + MsgTimeStamp() + "] "; } // write a line to the log file StreamWriter logFile = new StreamWriter(_ApplicationDirectory + _LogFileName, true); logFile.WriteLine(_MsgLevelText + logRecord); logFile.Close(); } catch (Exception) { throw; } } // PRIVATE METHODS private void CreateNewLogFile(ref FileInfo logFile) { try { string logFilePath = logFile.FullName; // write the log file header _MsgLevelText = "[Info @" + MsgTimeStamp() + "] "; string cpu = string.Empty; if (Environment.Is64BitOperatingSystem) { cpu = " (x64)"; } StreamWriter newLog = new StreamWriter(logFilePath, false); newLog.Flush(); newLog.WriteLine(_MsgLevelText + "===================================================================="); newLog.WriteLine(_MsgLevelText + "Team Foundation Server Administration Log"); newLog.WriteLine(_MsgLevelText + "Version : " + "1.0.0 Author: Bob Hardister"); newLog.WriteLine(_MsgLevelText + "DateTime : " + _LogTimestamp); newLog.WriteLine(_MsgLevelText + "Type : " + "OWS Custom TFS API Plug-in"); newLog.WriteLine(_MsgLevelText + "Activity : " + "Bug Auto Task Creation for CCB Approved Bugs"); newLog.WriteLine(_MsgLevelText + "Area : " + "Build Explorer"); newLog.WriteLine(_MsgLevelText + "Assembly : " + "Ows.TeamFoundation.BugAutoTaskCreation.PlugIns.dll"); newLog.WriteLine(_MsgLevelText + "Location : " + @"C:\Program Files\Microsoft Team Foundation Server 2010\Application Tier\Web Services\bin\Plugins"); newLog.WriteLine(_MsgLevelText + "User : " + Environment.UserDomainName + @"\" + Environment.UserName); newLog.WriteLine(_MsgLevelText + "Machine : " + Environment.MachineName); newLog.WriteLine(_MsgLevelText + "System : " + Environment.OSVersion + cpu); newLog.WriteLine(_MsgLevelText + "===================================================================="); newLog.WriteLine(_MsgLevelText); newLog.Close(); } catch (Exception) { throw; } } private string MsgTimeStamp() { string msgTimestamp = string.Empty; return msgTimestamp = DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss:fff"); } } }

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  • Snake Game Help

    - by MuhammadA
    I am making a snake game and learning XNA at the same time. I have 3 classes : Game.cs, Snake.cs and Apple.cs My problem is more of a conceptual problem, I want to know which class is really responsible for ... detecting collision of snake head on apple/itself/wall? which class should increase the snakes speed, size? It seems to me that however much I try and put the snake stuff into snake.cs that game.cs has to know a lot about the snake, like : -- I want to increase the score depending on size of snake, the score variable is inside game.cs, which means now I have to ask the snake its size on every hit of the apple... seems a bit unclean all this highly coupled code. or -- I DO NOT want to place the apple under the snake... now the apple suddenly has to know about all the snake parts, my head hurts when I think of that. Maybe there should be some sort of AppleLayer.cs class that should know about the snake... Whats the best approach in such a simple scenario? Any tips welcome. Game.cs : using System; using System.Collections.Generic; using System.Linq; using Microsoft.Xna.Framework; using Microsoft.Xna.Framework.Audio; using Microsoft.Xna.Framework.Content; using Microsoft.Xna.Framework.GamerServices; using Microsoft.Xna.Framework.Graphics; using Microsoft.Xna.Framework.Input; using Microsoft.Xna.Framework.Media; using Microsoft.Xna.Framework.Design; namespace Snakez { public enum CurrentGameState { Playing, Paused, NotPlaying } public class Game1 : Microsoft.Xna.Framework.Game { private GraphicsDeviceManager _graphics; private SpriteBatch _spriteBatch; private readonly Color _niceGreenColour = new Color(167, 255, 124); private KeyboardState _oldKeyboardState; private SpriteFont _scoreFont; private SoundEffect _biteSound, _crashSound; private Vector2 _scoreLocation = new Vector2(10, 10); private Apple _apple; private Snake _snake; private int _score = 0; private int _speed = 1; public Game1() { _graphics = new GraphicsDeviceManager(this); Content.RootDirectory = "Content"; } /// <summary> /// Allows the game to perform any initialization it needs to before starting to run. /// This is where it can query for any required services and load any non-graphic /// related content. Calling base.Initialize will enumerate through any components /// and initialize them as well. /// </summary> protected override void Initialize() { base.Initialize(); } /// <summary> /// LoadContent will be called once per game and is the place to load /// all of your content. /// </summary> protected override void LoadContent() { _spriteBatch = new SpriteBatch(GraphicsDevice); _scoreFont = Content.Load<SpriteFont>("Score"); _apple = new Apple(800, 480, Content.Load<Texture2D>("Apple")); _snake = new Snake(Content.Load<Texture2D>("BodyBlock")); _biteSound = Content.Load<SoundEffect>("Bite"); _crashSound = Content.Load<SoundEffect>("Crash"); } /// <summary> /// UnloadContent will be called once per game and is the place to unload /// all content. /// </summary> protected override void UnloadContent() { Content.Unload(); } /// <summary> /// Allows the game to run logic such as updating the world, /// checking for collisions, gathering input, and playing audio. /// </summary> /// <param name="gameTime">Provides a snapshot of timing values.</param> protected override void Update(GameTime gameTime) { KeyboardState newKeyboardState = Keyboard.GetState(); if (newKeyboardState.IsKeyDown(Keys.Escape)) { this.Exit(); // Allows the game to exit } else if (newKeyboardState.IsKeyDown(Keys.Up) && !_oldKeyboardState.IsKeyDown(Keys.Up)) { _snake.SetDirection(Direction.Up); } else if (newKeyboardState.IsKeyDown(Keys.Down) && !_oldKeyboardState.IsKeyDown(Keys.Down)) { _snake.SetDirection(Direction.Down); } else if (newKeyboardState.IsKeyDown(Keys.Left) && !_oldKeyboardState.IsKeyDown(Keys.Left)) { _snake.SetDirection(Direction.Left); } else if (newKeyboardState.IsKeyDown(Keys.Right) && !_oldKeyboardState.IsKeyDown(Keys.Right)) { _snake.SetDirection(Direction.Right); } _oldKeyboardState = newKeyboardState; _snake.Update(); if (_snake.IsEating(_apple)) { _biteSound.Play(); _score += 10; _apple.Place(); } base.Update(gameTime); } /// <summary> /// This is called when the game should draw itself. /// </summary> /// <param name="gameTime">Provides a snapshot of timing values.</param> protected override void Draw(GameTime gameTime) { GraphicsDevice.Clear(_niceGreenColour); float frameRate = 1 / (float)gameTime.ElapsedGameTime.TotalSeconds; _spriteBatch.Begin(); _spriteBatch.DrawString(_scoreFont, "Score : " + _score, _scoreLocation, Color.Red); _apple.Draw(_spriteBatch); _snake.Draw(_spriteBatch); _spriteBatch.End(); base.Draw(gameTime); } } } Snake.cs : using System; using System.Collections.Generic; using System.Linq; using System.Text; using Microsoft.Xna.Framework.Graphics; using Microsoft.Xna.Framework; namespace Snakez { public enum Direction { Up, Down, Left, Right } public class Snake { private List<Rectangle> _parts; private readonly Texture2D _bodyBlock; private readonly int _startX = 160; private readonly int _startY = 120; private int _moveDelay = 100; private DateTime _lastUpdatedAt; private Direction _direction; private Rectangle _lastTail; public Snake(Texture2D bodyBlock) { _bodyBlock = bodyBlock; _parts = new List<Rectangle>(); _parts.Add(new Rectangle(_startX, _startY, _bodyBlock.Width, _bodyBlock.Height)); _parts.Add(new Rectangle(_startX + bodyBlock.Width, _startY, _bodyBlock.Width, _bodyBlock.Height)); _parts.Add(new Rectangle(_startX + (bodyBlock.Width) * 2, _startY, _bodyBlock.Width, _bodyBlock.Height)); _parts.Add(new Rectangle(_startX + (bodyBlock.Width) * 3, _startY, _bodyBlock.Width, _bodyBlock.Height)); _direction = Direction.Right; _lastUpdatedAt = DateTime.Now; } public void Draw(SpriteBatch spriteBatch) { foreach (var p in _parts) { spriteBatch.Draw(_bodyBlock, new Vector2(p.X, p.Y), Color.White); } } public void Update() { if (DateTime.Now.Subtract(_lastUpdatedAt).TotalMilliseconds > _moveDelay) { //DateTime.Now.Ticks _lastTail = _parts.First(); _parts.Remove(_lastTail); /* add new head in right direction */ var lastHead = _parts.Last(); var newHead = new Rectangle(0, 0, _bodyBlock.Width, _bodyBlock.Height); switch (_direction) { case Direction.Up: newHead.X = lastHead.X; newHead.Y = lastHead.Y - _bodyBlock.Width; break; case Direction.Down: newHead.X = lastHead.X; newHead.Y = lastHead.Y + _bodyBlock.Width; break; case Direction.Left: newHead.X = lastHead.X - _bodyBlock.Width; newHead.Y = lastHead.Y; break; case Direction.Right: newHead.X = lastHead.X + _bodyBlock.Width; newHead.Y = lastHead.Y; break; } _parts.Add(newHead); _lastUpdatedAt = DateTime.Now; } } public void SetDirection(Direction newDirection) { if (_direction == Direction.Up && newDirection == Direction.Down) { return; } else if (_direction == Direction.Down && newDirection == Direction.Up) { return; } else if (_direction == Direction.Left && newDirection == Direction.Right) { return; } else if (_direction == Direction.Right && newDirection == Direction.Left) { return; } _direction = newDirection; } public bool IsEating(Apple apple) { if (_parts.Last().Intersects(apple.Location)) { GrowBiggerAndFaster(); return true; } return false; } private void GrowBiggerAndFaster() { _parts.Insert(0, _lastTail); _moveDelay -= (_moveDelay / 100)*2; } } } Apple.cs : using System; using System.Collections.Generic; using System.Linq; using System.Text; using Microsoft.Xna.Framework.Graphics; using Microsoft.Xna.Framework; namespace Snakez { public class Apple { private readonly int _maxWidth, _maxHeight; private readonly Texture2D _texture; private readonly Random random = new Random(); public Rectangle Location { get; private set; } public Apple(int screenWidth, int screenHeight, Texture2D texture) { _maxWidth = (screenWidth + 1) - texture.Width; _maxHeight = (screenHeight + 1) - texture.Height; _texture = texture; Place(); } public void Place() { Location = GetRandomLocation(_maxWidth, _maxHeight); } private Rectangle GetRandomLocation(int maxWidth, int maxHeight) { // x and y -- multiple of 20 int x = random.Next(1, maxWidth); var leftOver = x % 20; x = x - leftOver; int y = random.Next(1, maxHeight); leftOver = y % 20; y = y - leftOver; return new Rectangle(x, y, _texture.Width, _texture.Height); } public void Draw(SpriteBatch spriteBatch) { spriteBatch.Draw(_texture, Location, Color.White); } } }

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  • NullReferenceException when changing skin/theme via Application.Current.Resources

    - by CoolCat
    I am writing an wpf application with multiple skins. The code to switch theme is as below: try { Application.Current.Resources.MergedDictionaries.Add( resource ); } catch( Exception ex ) { } The first time the code is called (to switch to a new theme), it is executed successfully; however, any subsequent calls to the same code would throw System.NullReferenceException. The way I set up my themes are similar to what described here: http://www.codewrecks.com/blog/index.php/2008/05/22/simple-skinnable-and-theme-management-in-wpf-user-interface/. Has anyone seen this error before? How do I go about debugging this since the exception is thrown else where? Any help is greatly appreciated. StackTrace: at System.Windows.EffectiveValueEntry.GetFlattenedEntry(RequestFlags requests) at System.Windows.DependencyObject.EvaluateEffectiveValue(EntryIndex entryIndex, DependencyProperty dp, PropertyMetadata metadata, EffectiveValueEntry oldEntry, EffectiveValueEntry newEntry, OperationType operationType) at System.Windows.DependencyObject.UpdateEffectiveValue(EntryIndex entryIndex, DependencyProperty dp, PropertyMetadata metadata, EffectiveValueEntry oldEntry, EffectiveValueEntry& newEntry, Boolean coerceWithDeferredReference, OperationType operationType) at System.Windows.StyleHelper.ApplyStyleOrTemplateValue(FrameworkObject fo, DependencyProperty dp) at System.Windows.StyleHelper.InvalidateContainerDependents(DependencyObject container, FrugalStructList`1& exclusionContainerDependents, FrugalStructList`1& oldContainerDependents, FrugalStructList`1& newContainerDependents) at System.Windows.StyleHelper.DoStyleInvalidations(FrameworkElement fe, FrameworkContentElement fce, Style oldStyle, Style newStyle) at System.Windows.StyleHelper.UpdateStyleCache(FrameworkElement fe, FrameworkContentElement fce, Style oldStyle, Style newStyle, Style& styleCache) at System.Windows.FrameworkElement.OnStyleChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) at System.Windows.DependencyObject.OnPropertyChanged(DependencyPropertyChangedEventArgs e) at System.Windows.FrameworkElement.OnPropertyChanged(DependencyPropertyChangedEventArgs e) at System.Windows.DependencyObject.NotifyPropertyChange(DependencyPropertyChangedEventArgs args) at System.Windows.DependencyObject.UpdateEffectiveValue(EntryIndex entryIndex, DependencyProperty dp, PropertyMetadata metadata, EffectiveValueEntry oldEntry, EffectiveValueEntry& newEntry, Boolean coerceWithDeferredReference, OperationType operationType) at System.Windows.DependencyObject.InvalidateProperty(DependencyProperty dp) at System.Windows.FrameworkElement.UpdateStyleProperty() at System.Windows.TreeWalkHelper.InvalidateStyleAndReferences(DependencyObject d, ResourcesChangeInfo info, Boolean containsTypeOfKey) at System.Windows.TreeWalkHelper.OnResourcesChanged(DependencyObject d, ResourcesChangeInfo info, Boolean raiseResourceChangedEvent) at System.Windows.TreeWalkHelper.OnResourcesChangedCallback(DependencyObject d, ResourcesChangeInfo info) at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe) at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren) at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren) at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d) at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe) at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren) at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren) at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d) at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe) at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren) at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren) at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d) at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe) at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren) at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren) at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d) at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe) at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren) at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d) at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe) at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren) at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren) at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d) at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe) at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren) at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren) at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d) at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe) at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren) at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren) at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d) at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe) at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren) at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren) at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d) at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe) at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d) at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren) at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren) at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d) at System.Windows.DescendentsWalker`1.StartWalk(DependencyObject startNode, Boolean skipStartNode) at System.Windows.TreeWalkHelper.InvalidateOnResourcesChange(FrameworkElement fe, FrameworkContentElement fce, ResourcesChangeInfo info) at System.Windows.Application.InvalidateResourceReferenceOnWindowCollection(WindowCollection wc, ResourcesChangeInfo info) at System.Windows.ResourceDictionary.NotifyOwners(ResourcesChangeInfo info) at System.Windows.ResourceDictionary.OnMergedDictionariesChanged(Object sender, NotifyCollectionChangedEventArgs e) at System.Collections.ObjectModel.ObservableCollection`1.OnCollectionChanged(NotifyCollectionChangedEventArgs e) at System.Collections.ObjectModel.ObservableCollection`1.InsertItem(Int32 index, T item) at System.Windows.ResourceDictionaryCollection.InsertItem(Int32 index, ResourceDictionary item) at System.Collections.ObjectModel.Collection`1.Add(T item)

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