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  • Design question what pattern to use

    - by rahul
    Problem Description: We have a requirement of storing the snapshot of an entity temporarily in the database untill a certain period of time untill all the processes to approve the data are completed. Once all approvals are completed the data shall be permanantly persisted into the actual table. Example: 1) Consider an entity called "User". One way to create the user is through the "Create Account Process". 2) The "Create Account Process" shall capture all the information of the User and store it in a temporary table in the database. 3) The data shall be used by the "Account Approval Process" to run its verification process. 4. After all the verification is completed successfully, the User data shall be persisted to the actual table. Question: Where to store the user data entered during "Create Account Process". Additionally, User data should be editable till the verification process is complete.

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  • Factory Method Pattern using Generics-C#

    - by nanda
    Just I am learning Generics.When i have an Abstract Method pattern like : //Abstract Product interface IPage { string pageType(); } //Concerete Product 1 class ResumePage : IPage { public string pageType() { return "Resume Page"; } } //Concrete Product 2 class SummaryPage : IPage { public string pageType() { return "SummaryPage"; } } //Fcatory Creator class FactoryCreator { public IPage CreateOnRequirement(int i) { if (i == 1) return new ResumePage(); else { return new SummaryPage(); } } } //Client/Consumer void Main() { FactoryCreator c = new FactoryCreator(); IPage p; p = c.CreateOnRequirement(1); Console.WriteLine("Page Type is {0}", p.pageType()); p = c.CreateOnRequirement(2); Console.WriteLine("Page Type is {0}", p.pageType()); Console.ReadLine(); } how to convert the code using generics?

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  • IoC, Containers, and NServiceBus confusion

    - by andy
    Hey guys, here's my setup Castle Windsor is my container NServiceBus is itself using it's own container internally, Spring by default I'm implementing the PubSub config. Ok, if I have my Bus.Publish happening within my IWantToRunAtStartup class, then everything is fine. As a test for example on Run() we can start a timer and it'll go into a Service style loop. However, what if I want to abstract NServiceBus from my app, and have my app go: new CustomPulisherClass().Notify(ISomeMessage msg); In this situation, how do I implement CustomPublisherClass. My confusion is coming from the fact that NServiceBus is already running as a Service, it's already been "Started". How to I get at the correct instance of the Bus object? cheers andy

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  • Looking for a better design: A readonly in-memory cache mechanism

    - by Dylan Lin
    Hi all, I have a Category entity (class), which has zero or one parent Category and many child Categories -- it's a tree structure. The Category data is stored in a RDBMS, so for better performance, I want to load all categories and cache them in memory while launching the applicaiton. Our system can have plugins, and we allow the plugin authors to access the Category Tree, but they should not modify the cached items and the tree(I think a non-readonly design might cause some subtle bugs in this senario), only the system knows when and how to refresh the tree. Here are some demo codes: public interface ITreeNode<T> where T : ITreeNode<T> { // No setter T Parent { get; } IEnumerable<T> ChildNodes { get; } } // This class is generated by O/R Mapping tool (e.g. Entity Framework) public class Category : EntityObject { public string Name { get; set; } } // Because Category is not stateless, so I create a cleaner view class for Category. // And this class is the Node Type of the Category Tree public class CategoryView : ITreeNode<CategoryView> { public string Name { get; private set; } #region ITreeNode Memebers public CategoryView Parent { get; private set; } private List<CategoryView> _childNodes; public IEnumerable<CategoryView> ChildNodes { return _childNodes; } #endregion public static CategoryView CreateFrom(Category category) { // here I can set the CategoryView.Name property } } So far so good. However, I want to make ITreeNode interface reuseable, and for some other types, the tree should not be readonly. We are not able to do this with the above readonly ITreeNode, so I want the ITreeNode to be like this: public interface ITreeNode<T> { // has setter T Parent { get; set; } // use ICollection<T> instead of IEnumerable<T> ICollection<T> ChildNodes { get; } } But if we make the ITreeNode writable, then we cannot make the Category Tree readonly, it's not good. So I think if we can do like this: public interface ITreeNode<T> { T Parent { get; } IEnumerable<T> ChildNodes { get; } } public interface IWritableTreeNode<T> : ITreeNode<T> { new T Parent { get; set; } new ICollection<T> ChildNodes { get; } } Is this good or bad? Are there some better designs? Thanks a lot! :)

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  • Factory Method Implementation

    - by cedar715
    I was going through the 'Factory method' pages in SO and had come across this link. And this comment. The example looked as a variant and thought to implement in its original way: to defer instantiation to subclasses... Here is my attempt. Does the following code implements the Factory pattern of the example specified in the link? Please validate and suggest if this has to undergo any re-factoring. public class ScheduleTypeFactoryImpl implements ScheduleTypeFactory { @Override public IScheduleItem createLinearScheduleItem() { return new LinearScheduleItem(); } @Override public IScheduleItem createVODScheduleItem() { return new VODScheduleItem(); } } public class UseScheduleTypeFactory { public enum ScheduleTypeEnum { CableOnDemandScheduleTypeID, BroadbandScheduleTypeID, LinearCableScheduleTypeID, MobileLinearScheduleTypeID } public static IScheduleItem getScheduleItem(ScheduleTypeEnum scheduleType) { IScheduleItem scheduleItem = null; ScheduleTypeFactory scheduleTypeFactory = new ScheduleTypeFactoryImpl(); switch (scheduleType) { case CableOnDemandScheduleTypeID: scheduleItem = scheduleTypeFactory.createVODScheduleItem(); break; case BroadbandScheduleTypeID: scheduleItem = scheduleTypeFactory.createVODScheduleItem(); break; case LinearCableScheduleTypeID: scheduleItem = scheduleTypeFactory.createLinearScheduleItem(); break; case MobileLinearScheduleTypeID: scheduleItem = scheduleTypeFactory.createLinearScheduleItem(); break; default: break; } return scheduleItem; } }

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  • JFace Providers and MVC/MVP/etc.

    - by Alexey Romanov
    Where do the JFace providers belong in an MVP or MVC architecture? Or should Provider pattern be treated as a different way of View-Model separation? If so, is it the same as the ASP.NET Provider pattern? Is there an article on a proper design of JFace applications using Providers?

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  • Validation with State Pattern for Multi-Page Forms in ASP.NET

    - by philrabin
    I'm trying to implement the state pattern for a multi-page registration form. The data on each page will be accumulated and stored in a session object. Should validation (including service layer calls to the DB) occur on the page level or inside each state class? In other words, should the concrete implementation of IState be concerned with the validation or should it be given a fully populated and valid object? See "EmptyFormState" class below: namespace Example { public class Registrar { private readonly IState formEmptyState; private readonly IState baseInformationComplete; public RegistrarSessionData RegistrarSessionData { get; set;} public Registrar() { RegistrarSessionData = new RegistrarSessionData(); formEmptyState = new EmptyFormState(this); baseInformationComplete = new BasicInfoCompleteState(this); State = formEmptyState; } public IState State { get; set; } public void SubmitData(RegistrarSessionData data) { State.SubmitData(data); } public void ProceedToNextStep() { State.ProceedToNextStep(); } } //actual data stored in the session //to be populated by page public class RegistrarSessionData { public string FirstName { get; set; } public string LastName { get; set; } //will include values of all 4 forms } //State Interface public interface IState { void SubmitData(RegistrarSessionData data); void ProceedToNextStep(); } //Concrete implementation of IState //Beginning state - no data public class EmptyFormState : IState { private readonly Registrar registrar; public EmptyFormState(Registrar registrar) { this.registrar = registrar; } public void SubmitData(RegistrarSessionData data) { //Should Validation occur here? //Should each state object contain a validation class? (IValidator ?) //Should this throw an exception? } public void ProceedToNextStep() { registrar.State = new BasicInfoCompleteState(registrar); } } //Next step, will have 4 in total public class BasicInfoCompleteState : IState { private readonly Registrar registrar; public BasicInfoCompleteState(Registrar registrar) { this.registrar = registrar; } public void SubmitData(RegistrarSessionData data) { //etc } public void ProceedToNextStep() { //etc } } }

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  • Tracking the user function that threw the exception

    - by makerofthings7
    I've been given a large application with only one try..catch at the outer most level. This application also throws exceptions all the time, and is poorly documented. Is there any pattern I can implement that will tell me what user method is being called, the exception being thrown, and also the count of exceptions? I'm thinking of using a dictionary with reflection to get the needed information, but I'm not sure if this will work. What do you think?

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  • What's the best practice way to convert enum to string?

    - by dario
    Hi. I have enum like this: public enum ObectTypes { TypeOne, TypeTwo, TypeThree, ... TypeTwenty } then I need to convert this enum to string. Now Im doing this that way: public string ConvertToCustomTypeName(ObjectTypes typeObj) { string result = string.Empty; switch (typeObj) { case ObjectTypes.TypeOne: result = "This is type T123"; break; case ObjectTypes.TypeTwo: result = "This is type T234"; break; ... case ObjectTypes.TypeTwenty: result = "This is type last"; break; } return result; } Im quite sure that there is better way do do this, Im looking for some good practice solution. Thanks in advance.

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  • How does a WCF server inform a WCF client about changes? (Better solution then simple polling, e.g.

    - by Ian Ringrose
    see also "WCF push to client through firewall" I need to have a WCF client that connect to a WCF server, then when some of the data changes on the server the clients need to update its display. As there is likely to be a firewall between the clients and the server. All communications must be over HTTP The server can not make an (physical) outgoing call to the client. As I am writing both the client and the server I do not need to limit the solution to only using soap etc. I am looking for built in surport for "long polling" / "Comet" etc Thanks for the most informative answer from Drew Marsh on how to implement long polling in WCF. However I thought the main “selling point” of WCF was that you could do this sort of thing just by configuring the channels to be used in the config file. E.g I want a channel that logically two way but physically incoming only.

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  • What is the best testing pattern for checking that parameters are being used properly?

    - by Joseph
    I'm using Rhino Mocks to try to verify that when I call a certain method, that the method in turn will properly group items and then call another method. Something like this: //Arrange var bucketsOfFun = new BucketGame(); var balls = new List<IBall> { new Ball { Color = Color.Red }, new Ball { Color = Color.Blue }, new Ball { Color = Color.Yellow }, new Ball { Color = Color.Orange }, new Ball { Color = Color.Orange } }; //Act bucketsOfFun.HaveFunWithBucketsAndBalls(balls); //Assert ??? Here is where the trouble begins for me. My method is doing something like this: public void HaveFunWithBucketsAndBalls(IList<IBall> balls) { //group all the balls together according to color var blueBalls = GetBlueBalls(balls); var redBalls = GetRedBalls(balls); // you get the idea HaveFunWithABucketOfBalls(blueBalls); HaveFunWithABucketOfBalls(redBalls); // etc etc with all the different colors } public void HaveFunWithABucketOfBalls(IList<IBall> colorSpecificBalls) { //doing some stuff here that i don't care about //for the test i'm writing right now } What I want to assert is that each time I call HaveFunWithABucketOfBalls that I'm calling it with a group of 1 red ball, then 1 blue ball, then 1 yellow ball, then 2 orange balls. If I can assert that behavior then I can verify that the method is doing what I want it to do, which is grouping the balls properly. Any ideas of what the best testing pattern for this would be?

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  • How to design this class hierarchy?

    - by devoured elysium
    I have defined an Event class: Event and all the following classes inherit from Event: AEvent BEvent CEvent DEvent Now, with the info I gather from all these Event classes, I will make a chart. With AEvent and BEvent, I will generate points for that chart, while with CEvent and DEvent I will paint certain regions of the chart. Now, how should I signal this in my class hierarchy? Should I make AEvent and BEvent inherit from PointEvent while CEvent and DEvent inherit from RegionEvent, being that both RegionEvent and PointEvent inherit from Event? Should I add a field with an Enum to Event with 2 values, Point and Region, and each of the child classes set their value to it? Should I use some kind of pattern here? Which one? Thanks.

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  • doubleton pattern in C++

    - by benjamin button
    I am aware of the singleton pattern in C++. but what is the logic to get two instances of the object? is there any such pattern where we could easily get 2 pattern. for the logic i could think of is that i can change the singleton pattern itself to have two objects created inside the class.this works. but if the requirement grows like if i need only 3 or only 4 what is the deswign pattern that i could think of to qualify such requirement?

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  • Is ASP.NET MVC is really MVC? Or how to separate model from controller?

    - by Andrey
    Hi all, This question is a bit rhetorical. At some point i got a feeling that ASP.NET MVC is not that authentic implementation of MVC pattern. Or i didn't understood it. Consider following domain: electric bulb, switch and motion detector. They are connected together and when you enter the room motion detector switches on the bulb. If i want to represent them as MVC: switch is model, because it holds the state and contains logic bulb is view, because it presents the state of model to human motion detector is controller, because it converts user actions to generic model commands Switch has one private field (On/Off) as a State and two methods (PressOn, PressOff). If you call PressOn when it is Off it goes to On, if you call it again state doesn't change. Bulb can be replaced with buzzer, motion detector with timer or button, but the model still represent the same logic. Eventually system will have same behavior. This is how i understand classical MVC decomposition, please correct me if i am wrong. Now let's decompose it in ASP.Net MVC way. Bulb is still a view Controller will be switch + motion detector Model is some object that will just pass state to bulb. So the logic that defines behavior moves to controller. Question 1: Is my understanding of MVC and ASP.NET MVC correct? Question 2: If yes, do you agree that ASP.NET MVC is not 100% accurate implementation? And back to life. The final question is how to separate model from controller in case of ASP.NET MVC. There can be two extremes. Controller does basic stuff and call model to do all the logic. Another is controller does all the logic and model is just something like class with properties that is mapped to DB. Question 3: Where should i draw the line between this extremes? How to balance? Thanks, Andrey

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  • Interface Design Problem: Storing Result of Transactions

    - by jboyd
    Requirements: multiple sources of input (social media content) into a system multiple destinations of output (social media api's) sources and destinations WILL be added some pseudo: IContentProvider contentProvider = context.getBean("contentProvider"); List<Content> toPost = contentProvider.getContent(); for (Content c : toPost) { SocialMediaPresence smPresence = socialMediaService.getSMPresenceBySomeId(c.getDestId()); smPresence.hasTwitter(); smPresence.hasFacebook(); //just to show what this is smPresence.postContent(c); //post content could fail for some SM platforms, but shoulnd't be lost forever } So now I run out of steam, I need to know what content has been successfully posted, and if it hasn't gone too all platforms, or if another platform were added in the future that content needs to go out for it as well (therefore my content provider will need to not only know if content has gone out, but for what platforms). I'm not looking for code, although sample/pseudo is fine... I'm looking for an approach to this problem that I can implement

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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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  • Where UnityContainerElement in Unity 2?

    - by TheAbdalla
    I was in Unity 1.2, use the following code: UnityConfigurationSection UnitySection = (UnityConfigurationSection)ConfigurationManager.GetSection("Unity"); Dictionary<string, IUnityContainer> Containers = new Dictionary<string, IUnityContainer>(); foreach (UnityContainerElement element in UnitySection.Containers) { IUnityContainer container = new UnityContainer(); Containers.Add(element.Name, container); element.Configure(Containers[element.Name]); } but, I couldn't do so in the Unity 2.0 beta2, because The class 'UnityContainerElement' does not exist in Unity 2 beta2. How can I do this in the new version?

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  • Specification Pattern vs Spec in BDD

    - by cadmium
    I'm trying to explore Behavior Driven Design and Domain Driven Design. I'm getting that written specifications drive the tests in BDD, but also that business logic can be encapsulated using the specification pattern for re-use in domain objects and repositories, etc. Are these basically the same concept just used in different ways, used in conjunction together, or am I completely confusing the concepts? Please shed some light, if possible.

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  • UML Class Relationships

    - by 01010011
    Hi, I would like to confirm whether I am on the right track when identifying common UML class relationships. For example, is the relationship between: 1 a stackoverflow member and his/her stackoverflow user account categorized as a composition relationship or an aggregation relationship? At first I thought it was an association because this member "has a" account. However on second thought, I am thinking its composition because each "part" (user account) belongs to only one whole (user) at a time, meaning for as long as I am logged into stackoverflow, I have to use this one and only account until I log off. If I log back onto stackoverflow with a different account then its composition again. Do you agree? 2 a database and a person's user account an aggregation relationship? I think so because 1 database (the whole) can store 0...* number of user accounts (the parts) but another database can store the same user accounts. Finally, can anyone recommend a website that specializes in designing code using UML? Thanks in advance

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  • Database Replication OOD Pattern

    - by MrOnigiri
    Greetings fellow overflowers, After reading on MSDN about correct strategies on how to perform database replication, and understanding their suggestion on Master-Subordinate Incremental Replication. It left me wondering, what OOD design pattern should I use on this... The main elements of this strategy are the Acquirer, the Manipulator and the Writer. The first fetches data from the database and passes on to the second which might perform simple transformations to the data, before handling it to the final element, the writer, that writes the desired data on the destination Database. I thought about using the Chain of Responsibility pattern, but the Acquirer, Manipulator and Writer don't share a common role among theme, so It makes no sense. Should these elements be written as separate classes, or methods inside my service? Of course I'll be creating a DB Helper class as well, but that doesn't constitutes a problem. Wondering what your opinions on this are! Thanks for your replies

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  • Design suggestions for creating document management structure using hidden shares.

    - by focus.nz
    I need to add some document management functionality into my software. Documents will be grouped by company name and project name. The folders need to be accessed by the application using the id numbers of clients/projects, but also easily browsed by the end user using windows explorer. Clients and Projects will be stored in a database. I am thinking of having the software create the folders using the friendly name and then using a hidden share with the id number for the software to access the files. The folder structure would be something like this --Company 1 (Company-1234$) -- Project 101 (Project-101$) -- Project 102 (Project-102$) -- Project 103 (Project-103$) -- Company 2 (Company-5678$) -- Project 201 (Project-201$) -- Project 202 (Project-202$) -- Project 203 (Project-203$) So in the example above there would be a company called "Company 1" with a ID of "1234". When browsing the folders using windows explorer the user would see \\ServerName\Documents\Company1 and you could also access the same folder from \\ServerName\Documents\Company-1234$ By using the hidden share, if the company name changes or its renamed for some reason it doesn't break the link in the application because its using the hidden shared based on the ID that never changes. Will having hundreds (maybe thousands) or hidden shares on a server provide a huge performance hit? Does any one have any suggestions or alternatives to provide this feature?

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  • Pattern for managing reference count and object life

    - by Gopalakrishnan Subramani
    We have a serial port which is connected to hundreds of physical devices on the same wire. We have protocols like Modbus and Hart to handle the request and response between the application and devices. The question is related to managing the reference count of the channel. When no device is using the channel, the channel should be closed. public class SerialPortChannel { int refCount = 0; public void AddReference() { refCount++; } public void ReleaseReference() { refCount--; if (refCount <= 0) this.ReleasePort(); //This close the serial port } } For each device connected, we create a object for the device like device = new Device(); device.Attach(channel); //this calls channel.AddReference() When the device disconnect, device.Detach(channel); //this calls channel.ReleaseReference() I am not convinced by the reference count model. Are there any better way to handle this problem in .NET World?

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