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• Opinions on sensor / reading / alert database design

  - by Mark

  I've asked a few questions lately regarding database design, probably too many ;-) However I beleive I'm slowly getting to the heart of the matter with my design and am slowly boiling it down. I'm still wrestling with a couple of decisions regarding how "alerts" are stored in the database. In this system, an alert is an entity that must be acknowledged, acted upon, etc. Initially I related readings to alerts like this (very cut down) : - [Location] LocationId [Sensor] SensorId LocationId UpperLimitValue LowerLimitValue [SensorReading] SensorReadingId Value Status Timestamp [SensorAlert] SensorAlertId [SensorAlertReading] SensorAlertId SensorReadingId The last table is associating readings with the alert, because it is the reading that dictate that the sensor is in alert or not. The problem with this design is that it allows readings from many sensors to be associated with a single alert - whereas each alert is for a single sensor only and should only have readings for that sensor associated with it (should I be bothered that the DB allows this though?). I thought to simplify things, why even bother with the SensorAlertReading table? Instead I could do this: [Location] LocationId [Sensor] SensorId LocationId [SensorReading] SensorReadingId SensorId Value Status Timestamp [SensorAlert] SensorAlertId SensorId Timestamp [SensorAlertEnd] SensorAlertId Timestamp Basically I'm not associating readings with the alert now - instead I just know that an alert was active between a start and end time for a particular sensor, and if I want to look up the readings for that alert I can do. Obviously the downside is I no longer have any constraint stopping me deleting readings that occurred during the alert, but I'm not sure that the constraint is neccessary. Now looking in from the outside as a developer / DBA, would that make you want to be sick or does it seem reasonable? Is there perhaps another way of doing this that I may be missing? Thanks. EDIT: Here's another idea - it works in a different way. It stores each sensor state change, going from normal to alert in a table, and then readings are simply associated with a particular state. This seems to solve all the problems - what d'ya think? (the only thing I'm not sure about is calling the table "SensorState", I can't help think there's a better name (maybe SensorReadingGroup?) : - [Location] LocationId [Sensor] SensorId LocationId [SensorState] SensorStateId SensorId Timestamp Status IsInAlert [SensorReading] SensorReadingId SensorStateId Value Timestamp There must be an elegant solution to this!

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• Using Moq at Blend design time

  - by adrian hara

  This might be a bit out there, but suppose I want to use Moq in a ViewModel to create some design time data, like so: public class SomeViewModel { public SomeViewModel(ISomeDependency dependency) { if (IsInDesignMode) { var mock = new Mock<ISomeDependency>(); dependency = mock.Object; // this throws! } } } The mock could be set up to do some stuff, but you get the idea. My problem is that at design-time in Blend, this code throws an InvalidCastException, with the message along the lines of "Unable to cast object of type 'Castle.Proxies.ISomeDependencyProxy2b3a8f3188284ff0b1129bdf3d50d3fc' to type 'ISomeDependency'." While this doesn't necessarily look to be Moq related but Castle related, I hope the Moq example helps ;) Any idea why that is? Thanks!

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• Design question for WinForms (C#) app, using Entity Framework

  - by cdotlister

  I am planning on writing a small home budget application for myself, as a learning excercise. I have built my database (SQL Server), and written a small console application to interact with it, and test out scenarios on my database. Once I am happy, my next step would be to start building the application - but I am already wondering what the best/standard design would be. I am palnning on using Entity Framework for handling my database entities... then linq to sql/objects for getting the data, all running under a WinForms (for now) application. My plan (I've never used EF... and most of my development background is Web apps) is to have my database... with Entity Framework in it's own project.. which has the connection to the database. This project would expose methods such as 'GetAccount()', 'GetAccount(int accountId)' etc. I'd then have a service project that references my EF project. And on top of that, my GUI project, which makes the calls to my service project. But I am stuck. Lets say I have a screen that displays a list of Account types (Debit, Credit, Loan...). Once I have selected one, the next drop down shows a list of accounts I have that suite that account type. So, my OnChange event on my DropDown on the account type control will make a call to the serviceLayer project, 'GetAccountTypes()', and I would expect back a List< of Account Types. However, the AccountType object ... what is that? That can't be the AccountType object from my EF project, as my GUI project doesn't have reference to it. Would I have to have some sort of Shared Library, shared between my GUI and my Service project, with a custom built AccountType object? The GUI can then expect back a list of these. So my service layer would have a method: public List<AccountType> GetAccountTypes() That would then make a call to a custom method in my EF project, which would probably be the same as the above method, except, it returns an list of EF.Data.AccountType (The Entity Framework generated Account Type object). The method would then have the linq code to get the data as I want it. Then my service layer will get that object, and transform it unto my custom AccountType object, and return it to the GUI. Does that sound at all like a good plan?

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• Design patterns exercises

  - by lm

  Does anyone know site where can be found collection of design patterns exercises? Thanks in advance

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• Where did System.Design go?

  - by Nilbert

  I am making a C# project in which I am using ScintillaNet, and it says: The referenced assembly "ScintillaNet" could not be resolved because it has a dependency on "System.Design, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" which is not in the currently targeted framework ".NETFramework,Version=v4.0,Profile=Client". Please remove references to assemblies not in the targeted framework or consider retargeting your project. I tried adding a reference to System.Design, but it doesn't exist in my list. Do I need to download it somewhere? I have MS Visual Studio 10.

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• WCF - Compact Framework - Pull data from mobile client

  - by jagse

  Hello guys, I want to communicate xml serialized objects from the server to the client and the other way arround. Now it is (probably) easy to invoke methods from a mobile client (compact framework) using WCF, but is there a way so that the server can invoke methods on the client side or some other way to pull data from the client? I know that callback contracts are not available in the compact framework as you can see here: http://blogs.msdn.com/andrewarnottms/archive/2007/09/13/calling-wcf-services-from-netcf-3-5-using-compact-wcf-and-netcfsvcutil-exe.aspx Originally I thought of socket programming and of developing this by myself, then someone here mentioned WCF. But it seems like WCF only would work in a non mobile environment as I need callbacks. Anyone can help me with this? Is it possible to develop a two way communication with a desktop server and multiple mobile clients using WCF, or will I have to do socket programming? Thanks for any advice or any kind of help!

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• Entity Framework and Sql Server view question

  - by Sergio Romero

  Hi to all, For several reasons that I don't have the liberty to talk about, we are defining a view on our Sql Server 2005 database like so: CREATE VIEW [dbo].[MeterProvingStatisticsPoint] AS SELECT CAST(0 AS BIGINT) AS 'RowNumber', CAST(0 AS BIGINT) AS 'ProverTicketId', CAST(0 AS INT) AS 'ReportNumber', GETDATE() AS 'CompletedDateTime', CAST(1.1 AS float) AS 'MeterFactor', CAST(1.1 AS float) AS 'Density', CAST(1.1 AS float) AS 'FlowRate', CAST(1.1 AS float) AS 'Average', CAST(1.1 AS float) AS 'StandardDeviation', CAST(1.1 AS float) AS 'MeanPlus2XStandardDeviation', CAST(1.1 AS float) AS 'MeanMinus2XStandardDeviation' WHERE 0 = 1 The idea is that the Entity Framework will create an entity based on this query, which it does, but it generates it with an error that states the following: "warning 6002: The table/view 'Keystone_Local.dbo.MeterProvingStatisticsPoint' does not have a primary key defined. The key has been inferred and the definition was created as a read-only table/view." And it decides that the CompletedDateTime field will be this entity primary key. We are using EdmGen to generate the model. Is there a way not to have the entity framework include any field of this view as a primary key? Thanks for help.

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• Stumbling Through: Making a case for the K2 Case Management Framework

  I have recently attended a three-day training session on K2s Case Management Framework (CMF), a free framework built on top of K2s blackpearl workflow product, and I have come away with several different impressions for some of the different aspects of the framework.  Before we get into the details, what is the Case Management Framework?  It is essentially a suite of tools that, when used together, solve many common workflow scenarios.  The tool has been developed over time by K2 consultants that have realized they tend to solve the same problems over and over for various clients, so they attempted to package all of those common solutions into one framework.  Most of these common problems involve workflow process that arent necessarily direct and would tend to be difficult to model.  Such solutions could be achieved in blackpearl alone, but the workflows would be complex and difficult to follow and maintain over time.  CMF attempts to simplify such scenarios not so much by black-boxing the workflow processes, but by providing different points of entry to the processes allowing them to be simpler, moving the complexity to a middle layer.  It is not a solution in and of itself, development is still required to tie the pieces together. CMF is under continuous development, both a plus and a minus in that bugs are fixed quickly and features added regularly, but it may be difficult to know which versions are the most stable.  CMF is not an officially supported K2 product, which means you will not get technical support but you will get access to the source code. The example given of a business process that would fit well into CMF is that of a file cabinet, where each folder in said file cabinet is a case that contains all of the data associated with one complaint/customer/incident/etc. and various users can access that case at any time and take one of a set of pre-determined actions on it.  When I was given that example, my first thought was that any workflow I have ever developed in the past could be made to fit this model there must be more than just this model to help decide if CMF is the right solution.  As the training went on, we learned that one of the key features of CMF is SharePoint integration as each case gets a SharePoint site created for it, and there are a number of excellent web parts that can be used to design a portal for users to get at all the information on their cases.  While CMF does not require SharePoint, without it you will be missing out on a huge portion of functionality that CMF offers.  My opinion is that without SharePoint integration, you may as well write your workflows and other components the old fashioned way. When I heard that each case gets its own SharePoint site created for it, warning bells immediately went off in my head as I felt that depending on the data load, a CMF enabled solution could quickly overwhelm SharePoint with thousands of sites so we have yet another deciding factor for CMF:  Just how many cases will your solution be creating?  While it is not necessary to use the site-per-case model, it is one of the more useful parts of the framework.  Without it, you are losing a big chunk of what CMF has to offer. When it comes to developing on top of the Case Management Framework, it becomes a matter of configuring what makes up a case, what can be done to a case, where each action on a case should take the user, and then typing up actions to case statuses.  This last step is one that I immediately warmed up to, as just about every workflow Ive designed in the past needed some sort of mapping table to set the status of a work item based on the action being taken definitely one of those common solutions that it is good to see rolled up into a re-useable entity (and it gets a nice configuration UI to boot!).  This concept is a little different than traditional workflow design, in that you dont have to think of an end-to-end process around passing a case along a path, rather, you must envision the case as central object with workflow threads branching off of it and doing their own thing with the case data.  Certainly there can be certain workflow threads that get rather complex, but the idea is that they RELATE to the case, they dont BECOME the case (though it is still possible with action->status mappings to prevent certain actions in certain cases, so it isnt always a wide-open free for all of actions on a case). I realize that this description of the Case Management Framework merely scratches the surface on what the product actually can do, and I dont think Ive conclusively defined for what sort of business scenario you can make a case for Case Management Framework.  What I do hope to have accomplished with this post is to raise awareness of CMF there is a (free!) product out there that could potentially simplify a tangled workflow process and give (for free!) a very useful set of SharePoint web parts and a nice set of (free!) reports.  The best way to see if it will truly fit your needs is to give it a try did I mention it is FREE?  Er, ok, so it is free, but only obtainable at this time for K2 partnersDid you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• OOP Design for an Economy

  - by waiwai933

  Not sure where to start, so I'm just going to plow in. Let's say I'm trying to represent an economy in OOP. A basic design I've come up with is: class Person{ int $money; // Money someone has in wallet/purse int $bank_account_id; function getAmountOfMoney() function addMoney($amountToAdd) function subtractMoney($amountToSubtract) } class BankAccount{ int $money; // Money in Bank Account int $interest_per_year; function giveInterest() function depositMoney() // Calls $person->subtractMoney() function withdrawMoney() // Calls $person->addMoney() } Are there any design flaws here?

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• 'Design By Contract' in C#

  - by IAmCodeMonkey

  I wanted to try a little design by contract in my latest C# application and wanted to have syntax akin to: public string Foo() { set { Assert.IsNotNull(value); Assert.IsTrue(value.Contains("bar")); _foo = value; } } I know I can get static methods like this from a unit test framework, but I wanted to know if something like this was already built-in to the language or if there was already some kind of framework floating around. I can write my own Assert functions, just don't want to reinvent the wheel.

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• GoF design patterns

  - by Swami

  Anyone know of a good podcast on design patterns?

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• A good design pattern for almost similar objects

  - by Sam

  Hello, I have two websites that have an almost identical database schema. the only difference is that some tables in one website have 1 or 2 extra fields that the other and vice versa. I wanted to the same Database Access layer classes to will manipulate both websites. What can be a good design pattern that can be used to handle that little difference. for example, I have a method createAccount(Account account) in my DAO class but the implementation will be slightly different between website A and website B. I know design patterns don't depend on the language but FYI i m working with Perl. Thanks

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• Entity Framework Performance Problem

  - by Steve Horn

  I'm hoping that someone can help me understand how to overcome a performance problem I'm running into with the latest version of the Entity Framework. In my test, I created my model from a database consisting of around 80 tables. The problem that I'm running into is that the cost of the very first query I run on a thread is very expensive. If I run without pre-compiling views the first query takes anywhere from 5800 to 6600 milliseconds. If I pre-compile the views (see this article) I can get the initial query cost down to about 2800 to 3200 milliseconds. 3 seconds for each request is still unacceptable for my needs. Subsequent queries are very fast. Can you please help me understand how to eliminate the poor performance of the initial query? I'm using the version of entity framework that ships with Visual Studio 2010 RC.

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• Entity Framework 4 and Velocity

  - by Feryt

  Hi. Did you ever used EF4 and Velocity(or other caching framework) together? I found this blog post Tracing and Caching EF.

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• jQuery/Javascript framework efficiency

  - by Russell

  My latest project is using a javascript framework (jQuery), along with some plugins (validation, jquery-ui, datepicker, facebox, ...) to help make a modern web application. I am now finding pages loading slower than I am used to. After some js profiling (thanks VS2010!), it seems a lot of the time is taken procesing inside the framework. Now I understand the more complex the ui tools, the more processing needs to be done. The project is not yet at a large stage and I think would be average functions. At this stage I can see it is not going to scale well. I noticed things like the 'each' command in jQuery takes quite a lot of processing time. Have others experienced some extra latency using JS frameworks? How do I minimise their effect on page performance? Are there best practices on implementation using JS frameworks? Thanks

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• EF and design pattern

  - by kathy

  Hello, I’m working on a high volume transactional enterprise application(asp.net, windows app, oracle app as client) which has been designed using n-tire application and SOA architecture .The application was developed in the .NET platform utilizing C#,VB.NET, Framework 3.5 (I’m planning to upgrade to the , Framework 4.0), EF( EF in the data layer level) and WCF(WCF services in the service layer level) Since this is the first project using EF, and having read about using EF in n-tier and SOA applications, and the features available in the EF Feature, I have the following points: Which design pattern should I use in EF( Simple Entities, Change Set, Self-Tracking Entities and DTOs) in the data layer level In addition Which design pattern should I use in the other tier and layer to get the best practices of EF Thanks

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• Validate data using DataAnnotations with WPF & Entity Framework?

  - by Shimmy

  Hello is thee any way to validate using Data Using DataAnnotations in WPF & Entity Framework?

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• disadvantages of builder design pattern

  - by Ankur Agrawal

  What would be the disadvantages of using the builder design pattern. Are there any??

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• PHP Framework with full jQuery integration?

  - by coma

  i'm tired of reinventing the wheel on PHP and loving jQuery to death so which framework fits my needs?

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• Entity framework - exclude list of values

  - by DutrowLLC

  Is there a way to exclude a list of values for an object attribute when querying the database through entity framework? I tried to be slick and pull this number: List<String> StringList = new List<String>(); StringList.Add("ya_mama"); StringList.Add("has"); StringList.Add("fleas"); servicesEntities context = new servicesEntities(); var NoFleasQuery = (from x in context.person where !StringList.Any(y => y.CompareTo(x.the_string_I_dont_want_it_to_be) == 0) // <--- the part where I thought I was slick select x); ...it compiled, but after I ran it, it gave me this error: Unable to create a constant value of type 'Closure type'. Only primitive types ('such as Int32, String, and Guid') are supported in this context. 'Closure type'???? How about MY closure!!! Entity framework... you broke my heart.

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• Design pattern for cost calculator app?

  - by Anders Svensson

  Hi, I have a problem that I’ve tried to get help for before, but I wasn’t able to solve it then, so I’m trying to simplify the problem now to see if I can get some more concrete help with this because it is driving me crazy… Basically, I have a working (more complex) version of this application, which is a project cost calculator. But because I am at the same time trying to learn to design my applications better, I would like some input on how I could improve this design. Basically the main thing I want is input on the conditionals that (here) appear repeated in two places. The suggestions I got before was to use the strategy pattern or factory pattern. I also know about the Martin Fowler book with the suggestion to Refactor conditional with polymorphism. I understand that principle in his simpler example. But how can I do either of these things here (if any would be suitable)? The way I see it, the calculation is dependent on a couple of conditions: 1. What kind of service is it, writing or analysis? 2. Is the project small, medium or large? (Please note that there may be other parameters as well, equally different, such as “are the products new or previously existing?” So such parameters should be possible to add, but I tried to keep the example simple with only two parameters to be able to get concrete help) So refactoring with polymorphism would imply creating a number of subclasses, which I already have for the first condition (type of service), and should I really create more subclasses for the second condition as well (size)? What would that become, AnalysisSmall, AnalysisMedium, AnalysisLarge, WritingSmall, etc…??? No, I know that’s not good, I just don’t see how to work with that pattern anyway else? I see the same problem basically for the suggestions of using the strategy pattern (and the factory pattern as I see it would just be a helper to achieve the polymorphism above). So please, if anyone has concrete suggestions as to how to design these classes the best way I would be really grateful! Please also consider whether I have chosen the objects correctly too, or if they need to be redesigned. (Responses like "you should consider the factory pattern" will obviously not be helpful... I've already been down that road and I'm stumped at precisely how in this case) Regards, Anders The code (very simplified, don’t mind the fact that I’m using strings instead of enums, not using a config file for data etc, that will be done as necessary in the real application once I get the hang of these design problems): public abstract class Service { protected Dictionary<string, int> _hours; protected const int SMALL = 2; protected const int MEDIUM = 8; public int NumberOfProducts { get; set; } public abstract int GetHours(); } public class Writing : Service { public Writing(int numberOfProducts) { NumberOfProducts = numberOfProducts; _hours = new Dictionary<string, int> { { "small", 125 }, { "medium", 100 }, { "large", 60 } }; } public override int GetHours() { if (NumberOfProducts <= SMALL) return _hours["small"] * NumberOfProducts; if (NumberOfProducts <= MEDIUM) return (_hours["small"] * SMALL) + (_hours["medium"] * (NumberOfProducts - SMALL)); return (_hours["small"] * SMALL) + (_hours["medium"] * (MEDIUM - SMALL)) + (_hours["large"] * (NumberOfProducts - MEDIUM)); } } public class Analysis : Service { public Analysis(int numberOfProducts) { NumberOfProducts = numberOfProducts; _hours = new Dictionary<string, int> { { "small", 56 }, { "medium", 104 }, { "large", 200 } }; } public override int GetHours() { if (NumberOfProducts <= SMALL) return _hours["small"]; if (NumberOfProducts <= MEDIUM) return _hours["medium"]; return _hours["large"]; } } public partial class Form1 : Form { public Form1() { InitializeComponent(); List<int> quantities = new List<int>(); for (int i = 0; i < 100; i++) { quantities.Add(i); } comboBoxNumberOfProducts.DataSource = quantities; } private void comboBoxNumberOfProducts_SelectedIndexChanged(object sender, EventArgs e) { Service writing = new Writing((int) comboBoxNumberOfProducts.SelectedItem); Service analysis = new Analysis((int) comboBoxNumberOfProducts.SelectedItem); labelWriterHours.Text = writing.GetHours().ToString(); labelAnalysisHours.Text = analysis.GetHours().ToString(); } }

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• Entity Framework use of indexes and foreign keys

  - by David

  I want to be able to search a table quite quickly using the Entity Framework, say if I have a Contacts table, a JobsToDo table and a matrix table linking the two tables e.g Contacts_JobsToDo_Mtx and I specify two foreign keys in the Contacts_JobsToDo_Mtx table, if I wanted to search this Mtx table, do I need to specify an index on the two foreign keys? Or by the fact that they are two foreign keys are they considered indexed on them anyway? Will the Entity Framework be able to search through the Mtx table quickly without having to specfiy an index on both keys? Thanks!

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• C# Language Design: explicit interface implementation of an event

  - by ControlFlow

  Small question about C# language design :)) If I had an interface like this: interface IFoo { int Value { get; set; } } It's possible to explicitly implement such interface using C# 3.0 auto-implemented properties: sealed class Foo : IFoo { int IFoo.Value { get; set; } } But if I had an event in the interface: interface IFoo { event EventHandler Event; } And trying to explicitly implement it using field-like event: sealed class Foo : IFoo { event EventHandler IFoo.Event; } I will get the following compiler error: error CS0071: An explicit interface implementation of an event must use event accessor syntax I think that field-like events is the some kind of dualism for auto-implemented properties. So my question is: what is the design reason for such restriction done?

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• GUI Framework for flash (as3)

  - by widgisoft

  I can't seem to find any GUI framework's for as3 that are as good as any the applications I already see out on the web; Is this something most people code themselves or am I missing something in flash itself? I'm looking for dialogs/windows, buttons, text boxes, combos, drop downs, menus, etc etc and the ability to extend the components to make new ones. I'd also prefer it to be as3 but any others will do also. May need to elaborate a little.. I'm actually looking for a framework to allow me to create my own GUIs in flash, custom skins, colors, styles, etc.

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• ASP.NET MVC & ADO.NET Entity Framework clientside validation

  - by JK

  Using aspnet mvc2 with the model auto-generated by entity framework: Is it possible to tell entity framework to auto-annotate all fields? eg: If database field says not null then add [Required] If DB field is a nvarchar(x) then add [StringLength(x)] And so on? What if the field name contains the string "email" eg CustomerEmail - can I get EF to auto-annotate that with an appropriate annotation ([Regex()] maybe) As I understand it, if the model fields are annotated, and I use both Html.ValidationMessageFor() and use if (ModelState.IsValid) in my controller, then that is all I need to do to have basic clientside input validation working? Thanks

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