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  • My first c# app and first null object exception

    - by Fresheyeball
    Total noob here. This is my first c# attempt, its a console application that simulates a drinking game called 'Left Right Center'. In the console I receive the following: CONSOLE Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object at LeftRightCenter.MainClass.Main (System.String[] args) [0x00038] in /Users/apple/Projects/LearningC/LearningC/Main.cs:80 [ERROR] FATAL UNHANDLED EXCEPTION: System.NullReferenceException: Object reference not set to an instance of an object at LeftRightCenter.MainClass.Main (System.String[] args) [0x00038] in /Users/apple/Projects/LearningC/LearningC/Main.cs:80 C# using System; namespace LeftRightCenter { class Player { //fields private int _quarters = 4; public int Quarters { get{ return _quarters; } set{ _quarters += value; } } public Player (string name) { } } class Dice { Random random = new Random(); public int Roll () { random = new Random (); int diceSide; diceSide = random.Next (0, 6); diceSide = (diceSide > 2) ? 3 : diceSide; return diceSide; } } class MainClass { static int activePlayer = 0; static int theCup = 0; static Player[] thePlayers = { new Player ("Jessica"), new Player ("Isaac"), new Player ("Ed"), new Player ("Bella"), new Player ("Elisa"), new Player ("Fake RedHead"), new Player ("Linda"), new Player ("MJ"), new Player ("Irene"), new Player("Devin") }; static Dice[] theDice = new Dice[2]; private static void MoveQuarter (int direction) { int numberOfPlayers = thePlayers.Length - 1; switch (direction) { case 0: thePlayers [activePlayer].Quarters = -1; theCup++; break; case 1: thePlayers [activePlayer].Quarters = -1; int leftPlayer = (activePlayer == 0) ? numberOfPlayers : activePlayer - 1; thePlayers [leftPlayer].Quarters = +1; break; case 2: thePlayers [activePlayer].Quarters = -1; int rightPlayer = (activePlayer == numberOfPlayers) ? 0 : activePlayer + 1; thePlayers [rightPlayer].Quarters = +1; break; } } public static void Main (string[] args) { int cupEndPoint = thePlayers.Length * 4 - 1; while (theCup < cupEndPoint) { foreach (Dice rattle in theDice) { if (thePlayers [activePlayer].Quarters > 0) { MoveQuarter (rattle.Roll ()); // this line seems to be the problem } } Console.WriteLine ("{0} Quarters In the Cup", theCup); } } } } I have no idea what the problem is or why, and my googling have proven more use confusing than helpful.

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  • How should I design a correct OO design in case of a Business-logic wide operation

    - by Mithir
    EDIT: Maybe I should ask the question in a different way. in light of ammoQ's comment, I realize that I've done something like suggested which is kind of a fix and it is fine by me. But I still want to learn for the future, so that if I develop new code for operations similar to this, I can design it correctly from the start. So, if I got the following characteristics: The relevant input is composed from data which is connected to several different business objects All the input data is validated and cross-checked Attempts are made in order to insert the data to the DB All this is just a single operation from Business side prospective, meaning all of the cross checking and validations are just side effects. I can't think of any other way but some sort of Operator/Coordinator kind of Object which activates the entire procedure, but then I fall into a Functional-Decomposition kind of code. so is there a better way in doing this? Original Question In our system we have many complex operations which involve many validations and DB activities. One of the main Business functionality could have been designed better. In short, there were no separation of layers, and the code would only work from the scenario in which it was first designed at, and now there were more scenarios (like requests from an API or from other devices) So I had to redesign. I found myself moving all the DB code to objects which acts like Business to DB objects, and I've put all the business logic in an Operator kind of a class, which I've implemented like this: First, I created an object which will hold all the information needed for the operation let's call it InformationObject. Then I created an OperatorObject which will take the InformationObject as a parameter and act on it. The OperatorObject should activate different objects and validate or check for existence or any scenario in which the business logic is compromised and then make the operation according to the information on the InformationObject. So my question is - Is this kind of implementation correct? PS, this Operator only works on a single Business-wise Operation.

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  • What is the justification for Python's power operator associating to the right?

    - by Pieter Müller
    I am writing code to parse mathematical expression strings, and noticed that the order in which chained power operators are evaluated in Python differs from the order in Excel. From http://docs.python.org/reference/expressions.html: "Thus, in an unparenthesized sequence of power and unary operators, the operators are evaluated from right to left (this does not constrain the evaluation order for the operands): -1*2 results in -1."* This means that, in Python: 2**2**3 is evaluated as 2**(2**3) = 2**8 = 256 In Excel, it works the other way around: 2^2^3 is evaluated as (2^2)^3 = 4^3 = 64 I now have to choose an implementation for my own parser. The Excel order is easier to implement, as it mirrors the evaluation order of multiplication. I asked some people around the office what their gut feel was for the evaluation of 2^2^3 and got mixed responses. Does anybody know of any good reasons or conciderations in favour of the Python implementation? And if you don't have an answer, please comment with the result you get from gut feel - 64 or 256?

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  • Difference between Breadth First Search, and Iterative deepening

    - by theraven
    I understand BFS, and DFS, but for the life of me cannot figure out the difference between iterative deepening and BFS. Apparently Iterative deepening has the same memory usage as DFS, but I am unable to see how this is possible, as it just keeps expanding like BFS. If anyone can clarify that would be awesome. tree to work on if required: A / \ B C / / \ D E F

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  • Test-First development tool for SQL Server 2005?

    - by Jeff Jones
    For several years I have been using a testing tool called qmTest that allows me to do test-driven database development for some Firebird databases. I write a test for a new feature (table, trigger, stored procedure, etc.) until it fails, then modify the database until the test passes. If necessary, I do more work on the test until it fails again, then modify the database until the test passes. Once the test for the feature is complete and passes 100% of the time, I save it in a suite of other tests for the database. Before moving on to another test or a deployment, I run all the tests as a suite to make sure nothing is broken. Tests can have dependencies on other tests, and the results are recorded and displayed in a browser. Nothing new here, I am sure. Our shop is aiming toward standardizing on MSSQLServer and I want to use the same procedure for developing our databases. Does anyone know of tools that allow or encourage this kind of development? I believe the Team System does, but we do not own that at this point, and probably will not for some time. I am not opposed to scripting, but would welcome a more graphical environment. Any suggestions?

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  • EF Code First Detached Entity not updating object reference

    - by Alvaro
    I'm posting the exact entity: public class Person : ContactableEntity { public Plan Plan { get; set; } public int Record { get; set; } public int PersonTypeValue { get; set; } } I'm using the following code to update in a disconected context fashion: public void Update(DbSet MySet, object Obj) { MySet.Attach(Obj); var Entry = this.Entry(Obj); Entry.State = EntityState.Modified; this.SaveChanges(); } This is a method exposed by my dbContext Called this way: PersistentManager.Update(PersistentManager.Personas,UpdatedPersona); The problem is, EF will update any property but the referenced Plan object. Can someone tell me where is the mistake? In advance : the entity reaches the point of update with all the properties correctly set. EF just fails to update the FK in the Database (no exception though)

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  • Documenting mathematical logic in code

    - by Kiril Raychev
    Sometimes, although not often, I have to include math logic in my code. The concepts used are mostly very simple, but the resulting code is not - a lot of variables with unclear purpose, and some operations with not so obvious intent. I don't mean that the code is unreadable or unmaintainable, just that it's waaaay harder to understand than the actual math problem. I try to comment the parts which are hardest to understand, but there is the same problem as in just coding them - text does not have the expressive power of math. I am looking for a more efficient and easy to understand way of explaining the logic behind some of the complex code, preferably in the code itself. I have considered TeX - writing the documentation and generating it separately from the code. But then I'd have to learn TeX, and the documentation will not be in the code itself. Another thing I thought of is taking a picture of the mathematical notations, equations and diagrams written on paper/whiteboard, and including it in javadoc. Is there a simpler and clearer way? P.S. Giving descriptive names(timeOfFirstEvent instead of t1) to the variables actually makes the code more verbose and even harder too read.

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  • looking for a short explanation of fuzzy logic

    - by user613326
    Well i got the idea that basics of fuzzy logic are not that hard to grasp. And i got the feeling that someone might explain it to me in like 30 minutes. Just like i understand neural networks and am able to re-create the famous Xor problem. And go just beyond it and create 3 layer networks of x nodes. I'd like to understand fuzzy till a similar usefully level, in c# language. However the problem is face, I'd like to get concept right however i see many websites who include lots of errors in their basic explaining. Like for example showing pictures and use different numbers as shown in pictures to calculate, as if lots of people just copied stuff without noticing what they write down. While others for me go to deep in their math notation) To me that's very annoying to learn from. For me there is no need to re-invent wheel; Aforge already got a fuzzy logic framework. So what i am looking for are some good examples, good examples like how the neural XOR problem is solved. Is there anyone such a instructional resource out there; do you know a web page, or YouTube where it is shortly explained, what would you recommend me ? Note this article comes close; but it just doesnt nail it for me. After that i downloaded a bunch of free PDF's but most are academic and hard to read for me (i'm not English and dont have a special math degree). (i've been looking around a lot for this, good starter material about it is hard to find).

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  • Code First CTP4 Error Mapper

    - by user506062
    Why my type always returns 0? public class PartiesConfiguracao : EntityConfiguration<Parties> { public PartiesConfiguracao() { MapHierarchy() .Case<Parties>(parties => new { PartiesID = parties.ID, ShipInstructionID = parties.ShipInstruction.ID, ContactID = parties.Contact.ID, parties.Name, Type = 0, parties.CNPJ, parties.Address }) .Case<Shipper>(parties => new { Type = 1 }) .Case<Consignee>(parties => new { Type = 2 }) .Case<Notify>(parties => new { Type = 3 }) .Case<Forwarder>(parties => new { Type = 4 }) .ToTable("si_Parties"); } }

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  • Accessing a Class Member from a First-Class Function

    - by dbyrne
    I have a case class which takes a list of functions: case class A(q:Double, r:Double, s:Double, l:List[(Double)=>Double]) I have over 20 functions defined. Some of these functions have their own parameters, and some of them also use the q, r, and s values from the case class. Two examples are: def f1(w:Double) = (d:Double) => math.sin(d) * w def f2(w:Double, q:Double) = (d:Double) => d * q * w The problem is that I then need to reference q, r, and s twice when instantiating the case class: A(0.5, 1.0, 2.0, List(f1(3.0), f2(4.0, 0.5))) //0.5 is referenced twice I would like to be able to instantiate the class like this: A(0.5, 1.0, 2.0, List(f1(3.0), f2(4.0))) //f2 already knows about q! What is the best technique to accomplish this? Can I define my functions in a trait that the case class extends? EDIT: The real world application has 7 members, not 3. Only a small number of the functions need access to the members. Most of the functions don't care about them.

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  • Enable Configurator for Return Orders

    - by ChristineS-Oracle
    With release 12.2.4 for non-referenced RMAs, Order Management will allow you to configure the model from Sales Order / Quick Sales Order windows. This is only allowable when profile  OM: Enable Configuration UI for RMA is set to Yes.  All selected options must be returnable, as well as all included items. Order Management explodes included items and creates options and option classes in a way similar to outbound orders. The application creates all selected components with same line number but different option/component number.  Additionally, the application does not allow re-configuration and/or deletion of any line if any line in the same configuration is received, fulfilled, closed, cancelled, or split. For additional information refer to the Oracle Order Management Release Notes for Release 12.2.4 (Doc ID 1906521.1).

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  • Save VM properties with EF code first

    - by Julien
    I thought this would be simple but can't find any good examples. public Class BookVm : ImplementsPropertyChanged { public int BookId {get;set;} private bool _favorite; public bool Favorite { get { return _favorite; } set { _favorite = value; OnPropertyChanged("Favorite"); MyDbContext.SaveChanges() // this does not work } } Then in my XAML bound to Book <CheckBox Content="Favorite" IsChecked="{Binding Favorite}" /> How and when do I call SaveChanges() on my DatabaseContext? I don't want to implement a save button. If I intercept the PropertyChange event and call SaveChanges, nothing seems to happen. My object is modified in memory but the database does not see a change. My BookVm class is created on application startup like so: foreach (var book in MyDbContext.Books) Books.Add(book); Where Books is an ObservableCollection<Book> in my MainWindowVm

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  • Code First entity framework connection string

    - by Suneel Dixit
    I have 3 class projects in my solutions. 1. MVC4 project 2. Domain 3. Tests In the MVC4 project I have added a web.config file with the connection string as <add name="EfDbContext" connectionString="Data Source=.;Initial Catalog=SportsStore;Integrated Security=true;" providerName="System.Data.SqlClient"/> I have a class by name EfDbContext in Domain project which inherits DbContext. When I view the website in browser, I get the server not found error. I debugged the EfDbContext class and found that the Database.Connection.ConnectionString is set to \SqlExpress with database as EfDbContext. Why is that?

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  • Retrieving only the first record or record at a certain index in LINQ

    - by vik20000in
    While working with data it’s not always required that we fetch all the records. Many a times we only need to fetch the first record, or some records in some index, in the record set. With LINQ we can get the desired record very easily with the help of the provided element operators. Simple get the first record. If you want only the first record in record set we can use the first method [Note that this can also be done easily done with the help of the take method by providing the value as one].     List<Product> products = GetProductList();      Product product12 = (         from prod in products         where prod.ProductID == 12         select prod)         .First();   We can also very easily put some condition on which first record to be fetched.     string[] strings = { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };     string startsWithO = strings.First(s => s[0] == 'o');  In the above example the result would be “one” because that is the first record starting with “o”.  Also the fact that there will be chances that there are no value returned in the result set. When we know such possibilities we can use the FirstorDefault() method to return the first record or incase there are no records get the default value.        int[] numbers = {};     int firstNumOrDefault = numbers.FirstOrDefault();  In case we do not want the first record but the second or the third or any other later record then we can use the ElementAt() method. In the ElementAt() method we need to pass the index number for which we want the record and we will receive the result for that element.      int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };      int fourthLowNum = (         from num in numbers         where num > 5         select num )         .ElementAt(1); Vikram

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  • Automatically capitalize first letter of first word in a new sentence in LaTeX

    - by Tom Hagen
    I know one of LaTeX's bragging points is that it doesn't have this Microsoftish behavior. Nevertheless, it's sometimes useful. LaTeX already adds an extra space after you type a (non-backslashed) period, so it should be possible to make it automatically capitalize the following letter as well. Is there an obvious way to write a macro that does this, or is there a LaTeX package that does it already?

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  • A Question About the Expressive Power of Higher-Order Logical Reasoning Formalisms.

    - by Bubba88
    Hi! I do not really know if this is scientifically proven, but I've read in a book (It was a relatively modern AI book by Peter Norvig) that secon-order logical programming could be more expressive than existing first-order languages. The question is: Is it statistically/symbolically proven that higher-order predicate logics exceed first-order predicates in their expressive power? Or they just bring the modularity/convenience/maintainability to your knowledge bases? Additionally: If there is some kind of firm direction in which I could go seeking more expressive power than I have (I mean exactly the descriptive potential of the symbols I write in given semantics/syntax) - then I would be glad to hear just almost everything :) Thank you.

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  • Music Notation Editor - Refactoring view creation logic elsewhere

    - by Cyril Silverman
    Let me preface by saying that knowing some elementary music theory and music notation may be helpful in grasping the problem at hand. I'm currently building a Music Notation and Tablature Editor (in Javascript). But I've come to a point where the core parts of the program are more or less there. All functionality I plan to add at this point will really build off the foundation that I've created. As a result, I want to refactor to really solidify my code. I'm using an API called VexFlow to render notation. Basically I pass the parts of the editor's state to VexFlow to build the graphical representation of the score. Here is a rough and stripped down UML diagram showing you the outline of my program: In essence, a Part has many Measures which has many Notes which has many NoteItems (yes, this is semantically weird, as a chord is represented as a Note with multiple NoteItems, individual pitches or fret positions). All of the relationships are bi-directional. There are a few problems with my design because my Measure class contains the majority of the entire application view logic. The class holds the data about all VexFlow objects (the graphical representation of the score). It contains the graphical Staff object and the graphical notes. (Shouldn't these be placed somewhere else in the program?) While VexFlowFactory deals with actual creation (and some processing) of most of the VexFlow objects, Measure still "directs" the creation of all the objects and what order they are supposed to be created in for both the VexFlowStaff and VexFlowNotes. I'm not looking for a specific answer as you'd need a much deeper understanding of my code. Just a general direction to go in. Here's a thought I had, create an MeasureView/NoteView/PartView classes that contains the basic VexFlow objects for each class in addition to any extraneous logic for it's creation? but where would these views be contained? Do I create a ScoreView that is a parallel graphical representation of everything? So that ScoreView.render() would cascade down PartView and call render for each PartView and casade down into each MeasureView, etc. Again, I just have no idea what direction to go in. The more I think about it, the more ways to go seem to pop into my head. I tried to be as concise and simplistic as possible while still getting my problem across. Please feel free to ask me any questions if anything is unclear. It's quite a struggle trying to dumb down a complicated problem to its core parts.

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  • Making game constants/tables available to game logic classes/routines in a modular manner

    - by Extrakun
    Suppose I have a game where there are several predefined constants and charts (a XP chart, cost of goods and so on). Those could be defined at runtime, or load from files at start-up. The question is how should those logic routines access the constants and charts? For example, I could try using global variables, but that cause all classes relying on the variables to be tightly coupled with them.

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  • Reuse Business Logic between Web and API

    - by fesja
    We have a website and two mobile apps that connect through an API. All the platforms do the exactly same things. Right now the structure is the following: Website. It manages models, controllers, views for the website. It also executes all background tasks. So if a user create a place, everything is executed in this code. API. It manages models, controllers and return a JSON. If a user creates a place on the mobile app, the place is created here. After, we add a background task to update other fields. This background task is executed by the Website. We are redoing everything, so it's time to improve the approach. Which is the best way to reuse the business logic so I only need to code the insert/edit/delete of the place & other actions related in just one place? Is a service oriented approach a good idea? For example: Service. It has the models and gets, adds, updates and deletes info from the DB. Website. It send the info to the service, and it renders HTML. API. It sends info to the service, and it returns JSON. Some problems I have found: More initial work? Not sure.. It can work slower. Any experience? The benefits: We only have the business logic in one place, both for web and api. It's easier to scale. We can put each piece on different servers. Other solutions Duplicate the code and be careful not to forget anything (do tests!) DUplicate some code but execute background tasks that updates the related fields and executes other things (emails, indexing...) A "small" detail is we are 1.3 person in backend, for now ;)

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  • Music Notation Editor - Refactoring view creation logic elseware

    - by Cyril Silverman
    Let me preface by saying that knowing some elementary music theory and music notation may be helpful in grasping the problem at hand. I'm currently building a Music Notation and Tablature Editor (in Javascript). But I've come to a point where the core parts of the program are more or less there. All functionality I plan to add at this point will really build off the foundation that I've created. As a result, I want to refactor to really solidify my code. I'm using an API called VexFlow to render notation. Basically I pass the parts of the editor's state to VexFlow to build the graphical representation of the score. Here is a rough and stripped down UML diagram showing you the outline of my program: In essence, a Part has many Measures which has many Notes which has many NoteItems (yes, this is semantically weird, as a chord is represented as a Note with multiple NoteItems, individual pitches or fret positions). All of the relationships are bi-directional. There are a few problems with my design because my Measure class contains the majority of the entire application view logic. The class holds the data about all VexFlow objects (the graphical representation of the score). It contains the graphical Staff object and the graphical notes. (Shouldn't these be placed somewhere else in the program?) While VexFlowFactory deals with actual creation (and some processing) of most of the VexFlow objects, Measure still "directs" the creation of all the objects and what order they are supposed to be created in for both the VexFlowStaff and VexFlowNotes. I'm not looking for a specific answer as you'd need a much deeper understanding of my code. Just a general direction to go in. Here's a thought I had, create an MeasureView/NoteView/PartView classes that contains the basic VexFlow objects for each class in addition to any extraneous logic for it's creation? but where would these views be contained? Do I create a ScoreView that is a parallel graphical representation of everything? So that ScoreView.render() would cascade down PartView and call render for each PartView and casade down into each MeasureView, etc. Again, I just have no idea what direction to go in. The more I think about it, the more ways to go seem to pop into my head. I tried to be as concise and simplistic as possible while still getting my problem across. Please feel free to ask me any questions if anything is unclear. It's quite a struggle trying to dumb down a complicated problem to its core parts.

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  • Implementing Foreach Looping Logic in SSIS

    With SSIS, it is possible to implement looping logic into SSIS's control flow in order to define a repeating workflow in a package for each member of a collection of objects. Rob Sheldon explains how to use this valuable feature of SSIS. Get smart with SQL Backup ProGet faster, smaller backups with integrated verification.Quickly and easily DBCC CHECKDB your backups. Learn more.

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  • ADO.NET Data Services business logic processing

    a simple approach that provides business logic processing before forwarding data to the clients with ADO.NET Data Services.  read moreBy Siyamand AyubiDid 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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