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• What Language Feature Can You Just Not Live Without?

  - by akdom

  I always miss python's built-in doc strings when working in other languages. I know this may seem odd, but it allows me to cut down significantly on excess comments while still providing a clean description of my code and any interfaces therein. What Language Feature Can You Just Not Live Without? If someone were building a new language and they asked you what one feature they absolutely must include, what would it be? This is getting kind of long, so I figured I'd do my best to summarize: Paraphrased to be language agnostic. If you know of a language which uses something mentioned, please at it in the parenthesis to the right of the feature. And if you have a better format for this list, by all means try it out (if it doesn't seem to work, I'll just roll back). Regular Expressions ~ torial (Perl) Garbage Collection ~ SaaS Developer (Python, Perl, Ruby, Java, .NET) Anonymous Functions ~ Vinko Vrsalovic (Lisp, Python) Arithmetic Operators ~ Jeremy Ross (Python, Perl, Ruby, Java, C#, Visual Basic, C, C++, Pascal, Smalltalk, etc.) Exception Handling ~ torial (Python, Java, .NET) Pass By Reference ~ Chris (Python) Unified String Format WalloWizard (C#) Generics ~ torial (Python, Java, C#) Integrated Query Equivalent to LINQ ~ Vyrotek (C#) Namespacing ~ Garry Shutler () Short Circuit Logic ~ Adam Bellaire ()

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• C# Why can't I find Sum() of this HashSet. says "Arithmetic operation resulted in an overflow."

  - by user2332665

  I was trying to solve this problem projecteuler,problem125 this is my solution in python(just for understanding the logic) import math lim=10**8 found=set() for start in xrange(1,int(math.sqrt(lim))): sos = start*start for i in xrange(start+1,int(math.sqrt(lim))): sos += (i*i) if sos >= lim: break s=str(int(sos)) if s==s[::-1]: found.add(sos) print sum(found) the same code I wrote in C# is as follows using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace ConsoleApplication1 { class Program { public static bool isPalindrome(string s) { string temp = ""; for (int i=s.Length-1;i>=0;i-=1){temp+=s[i];} return (temp == s); } static void Main(string[] args) { int lim = Convert.ToInt32(Math.Pow(10,8)); var found = new HashSet<int>(); for (int start = 1; start < Math.Sqrt(lim); start += 1) { int s = start *start; for (int i = start + 1; start < Math.Sqrt(lim); i += 1) { s += i * i; if (s > lim) { break; } if (isPalindrome(s.ToString())) { found.Add(s); } } } Console.WriteLine(found.Sum()); } } } the code debugs fine until it gives an exception at Console.WriteLine(found.Sum()); (line31). Why can't I find Sum() of the set found

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• How to invalidate cache when benchmarking?

  - by Michael Buen

  I have this code, that when swapping the order of UsingAs and UsingCast, their performance also swaps. using System; using System.Diagnostics; using System.Linq; using System.IO; class Test { const int Size = 30000000; static void Main() { object[] values = new MemoryStream[Size]; UsingAs(values); UsingCast(values); Console.ReadLine(); } static void UsingCast(object[] values) { Stopwatch sw = Stopwatch.StartNew(); int sum = 0; foreach (object o in values) { if (o is MemoryStream) { var m = (MemoryStream)o; sum += (int)m.Length; } } sw.Stop(); Console.WriteLine("Cast: {0} : {1}", sum, (long)sw.ElapsedMilliseconds); } static void UsingAs(object[] values) { Stopwatch sw = Stopwatch.StartNew(); int sum = 0; foreach (object o in values) { if (o is MemoryStream) { var m = o as MemoryStream; sum += (int)m.Length; } } sw.Stop(); Console.WriteLine("As: {0} : {1}", sum, (long)sw.ElapsedMilliseconds); } } Outputs: As: 0 : 322 Cast: 0 : 281 When doing this... UsingCast(values); UsingAs(values); ...Results to this: Cast: 0 : 322 As: 0 : 281 When doing just this... UsingAs(values); ...Results to this: As: 0 : 322 When doing just this: UsingCast(values); ...Results to this: Cast: 0 : 322 Aside from running them independently, how to invalidate the cache so the second code being benchmarked won't receive the cached memory of first code? Benchmarking aside, just loved the fact that modern processors do this caching magic :-)

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• Are lambda expressions/delegates in C# "pure", or can they be?

  - by Bob

  I recently asked about functional programs having no side effects, and learned what this means for making parallelized tasks trivial. Specifically, that "pure" functions make this trivial as they have no side effects. I've also recently been looking into LINQ and lambda expressions as I've run across examples many times here on StackOverflow involving enumeration. That got me to wondering if parallelizing an enumeration or loop can be "easier" in C# now. Are lambda expressions "pure" enough to pull off trivial parallelizing? Maybe it depends on what you're doing with the expression, but can they be pure enough? Would something like this be theoretically possible/trivial in C#?: Break the loop into chunks Run a thread to loop through each chunk Run a function that does something with the value from the current loop position of each thread For instance, say I had a bunch of objects in a game loop (as I am developing a game and was thinking about the possibility of multiple threads) and had to do something with each of them every frame, would the above be trivial to pull off? Looking at IEnumerable it seems it only keeps track of the current position, so I'm not sure I could use the normal generic collections to break the enumeration into "chunks". Sorry about this question. I used bullets above instead of pseudo-code because I don't even know enough to write pseudo-code off the top of my head. My .NET knowledge has been purely simple business stuff and I'm new to delegates and threads, etc. I mainly want to know if the above approach is good for pursuing, and if delegates/lambdas don't have to be worried about when it comes to their parallelization.

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• How do I implement repository pattern and unit of work when dealing with multiple data stores?

  - by Jason

  I have a unique situation where I am building a DDD based system that needs to access both Active Directory and a SQL database as persistence. Initially this wasnt a problem because our design was setup where we had a unit of work that looked like this: public interface IUnitOfWork { void BeginTransaction() void Commit() } and our repositories looked like this: public interface IRepository<T> { T GetByID() void Save(T entity) void Delete(T entity) } In this setup our load and save would handle the mapping between both data stores because we wrote it ourselves. The unit of work would handle transactions and would contain the Linq To SQL data context that the repositories would use for persistence. The active directory part was handled by a domain service implemented in infrastructure and consumed by the repositories in each Save() method. Save() was responsible with interacting with the data context to do all the database operations. Now we are trying to adapt it to entity framework and take advantage of POCO. Ideally we would not need the Save() method because the domain objects are being tracked by the object context and we would just need to add a Save() method on the unit of work to have the object context save the changes, and a way to register new objects with the context. The new proposed design looks more like this: public interface IUnitOfWork { void BeginTransaction() void Save() void Commit() } public interface IRepository<T> { T GetByID() void Add(T entity) void Delete(T entity) } This solves the data access problem with entity framework, but does not solve the problem with our active directory integration. Before, it was in the Save() method on the repository, but now it has no home. The unit of work knows nothing other than the entity framework data context. Where should this logic go? I argue this design only works if you only have one data store using entity framework. Any ideas how to best approach this issue? Where should I put this logic?

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• Why can't I create a database in an empty ASP MVC 2 project using Project->Add->New Item->SQL Server

  - by Dr Dork

  I'm diving head first into ASP MVC and am playing around with creating and manipulating a database. I did a search and found this tutorial for creating a database, however when I follow it, I get this error when trying to add a new database to my fresh, empty ASP MVC 2 project... A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified) The only requirement the tutorial mentioned was SQL Server Express, but when I went to download it, it said it was already installed. I'm assuming it was part of the VS 2010 RC I installed and am running. So I don't know what else I need if I am missing something. This is all new to me, so I'm sure I'm missing something obvious here and after I'm done posting this question, I plan to do some more research into the topic of databases and how they work with ASP MVC. In the meantime, I was you could help me answer a couple high level questions... What am I missing/forgetting to do that is causing this error? Any suggestions for good resources/tutorials that focus on using databases with ASP MVC? I've done a lot of database programming in the past, so I'm familiar with the concepts of relational databases and the SQL language. I wish I could find a good resource for learning how to work with them in an ASP dev environment, as well as a good breakdown of all the related technologies used for working with them (i.e. LINQ to SQL). Thanks so much in advance for all your help! I'm going to start researching these questions right now.

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• How to form submit and show a different page in ASP.Net MVC?

  - by melaos

  hi guys i'm new to asp.net mvc.. so basically i just build up a two page app which takes the registration information of the user and post it to the database. i use a lot of jquery and ajax calls to retrieve data from the database using linq to sql stored proc object. and currently i'm stuck at one page where after the user submits the form it should redirect him to /Home/AddProduct. What i found was the error: Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.Web.HttpException: Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster. what used on my form are basically a combination of html controls, asp.net controls and some asp.net mvc type controls. i submit the form using action="/Home/ProductAdded" and after doing some googling i found i was supposed to add in the machine key but after doing so, the index page becomes unviewable. because it couldn't find the index file now. removing the action helps, but now it just doesn't go anywhere. so what am i missing here? i feel i'm missing a lot of fundamentals understanding about asp.net mvc and i don't even know how to submit a form and go to a different page here!!

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• What's the best way to develop a debugging window for an ajax ASP.Net MVC application

  - by KallDrexx

  While developing my ASP.NET MVC, I have started to see the need for a debugging console window to assist in figuring out what is going right and wrong in my code. I read the last few chapters of the Pro Asp.net MVC book, and the author details how to use http modules to show page load/creation times and linq to sql query logs, both of which I definitely want to be able to see. However, since I am loading a lot of small sections of my page individually with ajax I don't want the debug information right there in the middle of my screen. So the idea I came up with was to have a separate browser window (open-able by a link or some javascript) with a console log, that can contain logged entries both from javascript and from the asp.net mvc run. The former should be relatively easy, but I'm having trouble coming up with a way to log the asp.net information in ajax requests. The direction I have been thinking of going is to create an httpmodule (like the Pro MVC book does), and have that module contain some that append the javascript's log to console calls with the messages. The issue I see with this is finding a way to get the log messages from the controller's action methods to the httpmodule's methods. The only way I see to do this is with a singleton, but I'm not sure if singletons are bad practice for a stateless web application. Furthermore, it seems like if I return json with my ajax calls (instead of pure html) then that won't work at all anyways and unless there is a way to add data to an existing json structure inside the httpmodule. How does everyone else handle this type of debugging in heavily ajax applications? For reference, the javascript library I am using is jquery.

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• Use the repository pattern when using PLINQO generated data?

  - by Chad

  I'm "upgrading" an MVC app. Previously, the DAL was a part of the Model, as a series of repositories (based on the entity name) using standard LINQ to SQL queries. Now, it's a separate project and is generated using PLINQO. Since PLINQO generates query extensions based on the properties of the entity, I started using them directly in my controller... and eliminated the repositories all together. It's working fine, this is more a question to draw upon your experience, should I continue down this path or should I rebuild the repositories (using PLINQO as the DAL within the repository files)? One benefit of just using the PLINQO generated data context is that when I need DB access, I just make one reference to the the data context. Under the repository pattern, I had to reference each repository when I needed data access, sometimes needing to reference multiple repositories on a single controller. The big benefit I saw on the repositories, were aptly named query methods (i.e. FindAllProductsByCategoryId(int id), etc...). With the PLINQO code, it's _db.Product.ByCatId(int id) - which isn't too bad either. I like both, but where it gets "harrier" is when the query uses predicates. I can roll that up into the repository query method. But on the PLINQO code, it would be something like _db.Product.Where(x = x.CatId == 1 && x.OrderId == 1); I'm not so sure I like having code like that in my controllers. Whats your take on this?

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• C#, finding the largest prime factor of a number

  - by Juan

  Hello! I am new at programming and I am practicing my C# programming skills. My application is meant to find the largest prime factor of a number entered by the user. But my application is not returning the right answer and I dont really know where the problem is. Can you please help me? using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace ConsoleApplication1 { class Program { static void Main(string[] args) { Console.WriteLine("Calcular máximo factor primo de n. De 60 es 5."); Console.Write("Escriba un numero: "); long num = Convert.ToInt64(Console.ReadLine()); long mfp = maxfactor(num); Console.WriteLine("El maximo factor primo es: " + num); Console.Read(); } static private long maxfactor (long n) { long m=1 ; bool en= false; for (long k = n / 2; !en && k > 1; k--) { if (n % k == 0 && primo(k)) { m = k; en = true; } } return m; } static private bool primo(long x) { bool sp = true; for (long i = 2; i <= x / 2; i++) { if (x % i == 0) sp = false; } return sp; } } }

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• Change in behaviour & generation of nullreference exception

  - by peril brain

  I made this program 2hr ago and it ran quit well when i confronted this to presaved .xls file. But when i closed that and started new instance,it started generating null refrence exception why??plz explain. using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.IO; using System.Threading; using Microsoft.Office.Interop; using Excel = Microsoft.Office.Interop.Excel; namespace svchost { class MainClass { Excel.Application oExcelApp; static void Main(string[] args) { MainClass mc = new MainClass(); while (true) { if (mc.chec()) { Console.WriteLine("RUNNING"); Thread.Sleep(4000); } else { Console.WriteLine("NOT RUNNING"); Thread.Sleep(8000); } } } public bool chec() { try { oExcelApp = (Excel.Application)System.Runtime.InteropServices.Marshal.GetActiveObject("Excel.Application"); Excel.Workbook xlwkbook = (Excel.Workbook)oExcelApp.ActiveWorkbook; //****PROBLEM FROM HERE********* Console.WriteLine(xlwkbook.Name + "\n"); ke kw = new ke(ref oExcelApp,ref xlwkbook); Console.WriteLine(xlwkbook.Author); xlwkbook = null; } catch (Exception ec) { oExcelApp = null; System.GC.Collect(); Console.WriteLine(ec); return false; } oExcelApp = null; System.GC.Collect(); return true; } } class ke { public ke(ref Excel.Application a1, ref Excel.Workbook b1) { Excel.Worksheet ws = (Excel.Worksheet)a1.ActiveSheet; Console.WriteLine(a1.ActiveWorkbook.Name + "\n" + ws.Name); Excel.Range rn; rn = ws.Cells.Find("657/07", Type.Missing, Excel.XlFindLookIn.xlValues, Excel.XlLookAt.xlPart, Excel.XlSearchOrder.xlByRows, Excel.XlSearchDirection.xlNext, false, Type.Missing, Type.Missing); Console.WriteLine(rn.Text); } } }

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• Does WPF break an Entity Framework ObjectContext?

  - by David Veeneman

  I am getting started with Entity Framework 4, and I am getting ready to write a WPF demo app to learn EF4 better. My LINQ queries return IQueryable<T>, and I know I can drop those into an ObservableCollection<T> with the following code: IQueryable<Foo> fooList = from f in Foo orderby f.Title select f; var observableFooList = new ObservableCollection<Foo>(fooList); At that point, I can set the appropriate property on my view model to the observable collection, and I will get WPF data binding between the view and the view model property. Here is my question: Do I break the ObjectContext when I move my foo list to the observable collection? Or put another way, assuming I am otherwise handling my ObjectContext properly, will EF4 properly update the model (and the database)? The reason why I ask is this: NHibernate tracks objects at the collection level. If I move an NHibernate IList<T> to an observable collection, it breaks NHibernate's change tracking mechanism. That means I have to do some very complicated object wrapping to get NHibernate to work with WPF. I am looking at EF4 as a way to dispense with all that. So, to get EF4 working with WPF, is it as simple as dropping my IQueryable<T> results into an ObservableCollection<T>. Does that preserve change-tracking on my EDM entity objects? Thanks for your help.

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• Pair-wise iteration in C# or sliding window enumerator

  - by f3lix

  If I have an IEnumerable like: string[] items = new string[] { "a", "b", "c", "d" }; I would like to loop thru all the pairs of consecutive items (sliding window of size 2). Which would be ("a","b"), ("b", "c"), ("c", "d") My solution was is this public static IEnumerable<Pair<T, T>> Pairs(IEnumerable<T> enumerable) { IEnumerator<T> e = enumerable.GetEnumerator(); e.MoveNext(); T current = e.Current; while ( e.MoveNext() ) { T next = e.Current; yield return new Pair<T, T>(current, next); current = next; } } // used like this : foreach (Pair<String,String> pair in IterTools<String>.Pairs(items)) { System.Out.PrintLine("{0}, {1}", pair.First, pair.Second) } When I wrote this code, I wondered if there are already functions in the .NET framework that do the same thing and do it not just for pairs but for any size tuples. IMHO there should be a nice way to do this kind of sliding window operations. I use C# 2.0 and I can imagine that with C# 3.0 (w/ LINQ) there are more (and nicer) ways to do this, but I'm primarily interested in C# 2.0 solutions. Though, I will also appreciate C# 3.0 solutions.

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• Retrive data from two tables in asp.net mvc using ADO.Net Entity Framework

  - by user192972

  Please read my question carefully and reply me. I have two tables as table1 and table2. In table1 i have columns as AddressID(Primary Key),Address1,Address2,City In table2 i have columns as ContactID(Primary Key),AddressID(Foriegn Key),Last Name,First Name. By using join operation i can retrive data from both the tables. I created a Model in my MVC Application.I can see both the tables in enitity editor. In the ViewData folder of my solution explorer i created two class as ContactViewData.cs and SLXRepository.cs In the ContactViewData.cs i have following code public IEnumerable<CONTACT> contacts { get; set; } In the SLXRepository.cs i have following code public IEnumerable<CONTACT> GetContacts() { var contact = ( from c in context.CONTACT join a in context.ADDRESS on c.ADDRESSID equals a.ADDRESSID select new { a.ADDRESS1, a.ADDRESS2, a.CITY, c.FIRSTNAME, c.LASTNAME } ); return contact; } I am getting the error in return type Cannot implicitly convert type 'System.Linq.IQueryable' to 'System.Collections.Generic.IEnumerable'. An explicit conversion exists (are you missing a cast?)

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• SQL Express under IIS 7.5

  - by fampinheiro

  I´m developing a web service that access a SQL Express database, it works very well in the Visual Studio host but when i deploy it to IIS 7.5 i get this exception. Please help me. Stack Trace: System.Data.EntityException: The underlying provider failed on Open. ---> System.Data.SqlClient.SqlException: Failed to generate a user instance of SQL Server due to failure in retrieving the user's local application data path. Please make sure the user has a local user profile on the computer. The connection will be closed. at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection) at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj) at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj) at System.Data.SqlClient.SqlInternalConnectionTds.CompleteLogin(Boolean enlistOK) at System.Data.SqlClient.SqlInternalConnectionTds.AttemptOneLogin(ServerInfo serverInfo, String newPassword, Boolean ignoreSniOpenTimeout, Int64 timerExpire, SqlConnection owningObject) at System.Data.SqlClient.SqlInternalConnectionTds.LoginNoFailover(String host, String newPassword, Boolean redirectedUserInstance, SqlConnection owningObject, SqlConnectionString connectionOptions, Int64 timerStart) at System.Data.SqlClient.SqlInternalConnectionTds.OpenLoginEnlist(SqlConnection owningObject, SqlConnectionString connectionOptions, String newPassword, Boolean redirectedUserInstance) at System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, Object providerInfo, String newPassword, SqlConnection owningObject, Boolean redirectedUserInstance) at System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection) at System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnection owningConnection, DbConnectionPool pool, DbConnectionOptions options) at System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject) at System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject) at System.Data.ProviderBase.DbConnectionPool.GetConnection(DbConnection owningObject) at System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection owningConnection) at System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory) at System.Data.SqlClient.SqlConnection.Open() at System.Data.EntityClient.EntityConnection.OpenStoreConnectionIf(Boolean openCondition, DbConnection storeConnectionToOpen, DbConnection originalConnection, String exceptionCode, String attemptedOperation, Boolean& closeStoreConnectionOnFailure) --- End of inner exception stack trace --- at System.Data.EntityClient.EntityConnection.OpenStoreConnectionIf(Boolean openCondition, DbConnection storeConnectionToOpen, DbConnection originalConnection, String exceptionCode, String attemptedOperation, Boolean& closeStoreConnectionOnFailure) at System.Data.EntityClient.EntityConnection.Open() at System.Data.Objects.ObjectContext.EnsureConnection() at System.Data.Objects.ObjectQuery`1.GetResults(Nullable`1 forMergeOption) at System.Data.Objects.ObjectQuery`1.System.Collections.Generic.IEnumerable<T>.GetEnumerator() at System.Linq.Enumerable.FirstOrDefault[TSource](IEnumerable`1 source) at WSCinema.CinemaService.Movie() in D:\Documents\My Dropbox\Projects\sd.v0910\trab3\code\WSCinema\CinemaService.asmx.cs:line 46

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• Instead of trigger in SQL Server - looses SCOPE_IDENTITY?

  - by kastermester

  Hey StackOverflow, I am (once again) having some issues with some SQL. I have a table, on which I have created an INSTEAD OF trigger to enforce some buissness rules (rules not really important). This works as intended. My issue is, that now when inserting data into this table, SCOPE_IDENTITY() now returns a NULL value, rather than the actual inserted identity, my guess is that this is because it is now out of scope - but then how do I get this in scope? I am using SQL Server 2008. Per request, here's the SQL: Insert + Scope code INSERT INTO [dbo].[Payment]([DateFrom], [DateTo], [CustomerId], [AdminId]) VALUES ('2009-01-20', '2009-01-31', 6, 1) SELECT SCOPE_IDENTITY() Trigger: CREATE TRIGGER [dbo].[TR_Payments_Insert] ON [dbo].[Payment] INSTEAD OF INSERT AS BEGIN -- SET NOCOUNT ON added to prevent extra result sets from -- interfering with SELECT statements. SET NOCOUNT ON; IF NOT EXISTS(SELECT 1 FROM dbo.Payment p INNER JOIN Inserted i ON p.CustomerId = i.CustomerId WHERE (i.DateFrom >= p.DateFrom AND i.DateFrom <= p.DateTo) OR (i.DateTo >= p.DateFrom AND i.DateTo <= p.DateTo) ) AND NOT EXISTS (SELECT 1 FROM Inserted p INNER JOIN Inserted i ON p.CustomerId = i.CustomerId WHERE (i.DateFrom <> p.DateFrom AND i.DateTo <> p.DateTo) AND ((i.DateFrom >= p.DateFrom AND i.DateFrom <= p.DateTo) OR (i.DateTo >= p.DateFrom AND i.DateTo <= p.DateTo)) ) BEGIN INSERT INTO dbo.Payment (DateFrom, DateTo, CustomerId, AdminId) SELECT DateFrom, DateTo, CustomerId, AdminId FROM Inserted END ELSE BEGIN ROLLBACK TRANSACTION END END The code did work before the creation of this trigger, also I am using LINQ to SQL in C# and as far as I can see, I have no way of changing SCOPE_IDENTITY to @@IDENITY - is there really no way out of this one?

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• WPF, C# - Making Intellisense/Autocomplete list, fastest way to filter list of strings

  - by user559548

  Hello everyone, I'm writing an Intellisense/Autocomplete like the one you find in Visual Studio. It's all fine up until when the list contains probably 2000+ items. I'm using a simple LINQ statement for doing the filtering: var filterCollection = from s in listCollection where s.FilterValue.IndexOf(currentWord, StringComparison.OrdinalIgnoreCase) >= 0 orderby s.FilterValue select s; I then assign this collection to a WPF Listbox's ItemSource, and that's the end of it, works fine. Noting that, the Listbox is also virtualised as well, so there will only be at most 7-8 visual elements in memory and in the visual tree. However the caveat right now is that, when the user types extremely fast in the richtextbox, and on every key up I execute the filtering + binding, there's this semi-race condition, or out of sync filtering, like the first key stroke's filtering could still be doing it's filtering or binding work, while the fourth key stroke is also doing the same. I know I could put in a delay before applying the filter, but I'm trying to achieve a seamless filtering much like the one in Visual Studio. I'm not sure where my problem exactly lies, so I'm also attributing it to IndexOf's string operation, or perhaps my list of string's could be optimised in some kind of index, that could speed up searching. Any suggestions of code samples are much welcomed. Thanks.

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• What is the name of this geometrical function?

  - by Spike

  In a two dimentional integer space, you have two points, A and B. This function returns an enumeration of the points in the quadrilateral subset bounded by A and B. A = {1,1} B = {2,3} Fn(A,B) = {{1,1},{1,2},{1,3},{2,1},{2,2},{2,3}} I can implement it in a few lines of LINQ. private void UnknownFunction(Point to, Point from, List<Point> list) { var vectorX = Enumerable.Range(Math.Min(to.X, from.X), Math.Abs(to.X - from.Y) + 1); var vectorY = Enumerable.Range(Math.Min(to.Y, from.Y), Math.Abs(to.Y - from.Y) + 1); foreach (var x in vectorX) foreach (var y in vectorY) list.Add(new Point(x, y)); } I'm fairly sure that this is a standard mathematical operation, but I can't think what it is. Feel free to tell me that it's one line of code in your language of choice. Or to give me a cunning implementation with lambdas or some such. But mostly I just want to know what it's called. It's driving me nuts. It feels a little like a convolution, but it's been too long since I was at school for me to be sure.

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• C# CreateElement method - how to add an child element with xmlns=""

  - by NealWalters

  How can I get the following code to add the element with "xmlns=''"? using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Xml; namespace ConsoleApplication1 { class Program { static void Main(string[] args) { string strXML = "<myroot>" + " <group3 xmlns='myGroup3SerializerStyle'>" + " <firstname xmlns=''>Neal3</firstname>" + " </group3>" + "</myroot>"; XmlDocument xmlDoc = new XmlDocument(); xmlDoc.LoadXml(strXML); XmlElement elem = xmlDoc.CreateElement(null, "lastname", null); elem.InnerText = "New-Value"; string strXPath = "/myroot/*[local-name()='group3' and namespace-uri()='myGroup3SerializerStyle']/firstname"; XmlNode insertPoint = xmlDoc.SelectSingleNode(strXPath); insertPoint.AppendChild(elem); string resultOuter = xmlDoc.OuterXml; Console.WriteLine("\n resultOuter=" + resultOuter); Console.ReadLine(); } } } My current output: resultOuter=<myroot><group3 xmlns="myGroup3SerializerStyle"><firstname xmlns="" >Neal3<lastname>New-Value</lastname></firstname></group3></myroot> The desired output: resultOuter=<myroot><group3 xmlns="myGroup3SerializerStyle"><firstname xmlns="" >Neal3<lastname xmlns="">New-Value</lastname></firstname></group3></myroot> For background, see related posts: http://www.stylusstudio.com/ssdn/default.asp?fid=23 (today) http://stackoverflow.com/questions/2410620/net-xmlserializer-to-element-formdefaultunqualified-xml (March 9, thought I fixed it, but bit me again today!)

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• what does this asp.net mvc compile time error states?

  - by Pandiya Chendur

  I have a repository class and it has this, using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.Mvc; using CrMVC.BusinessObjects; namespace CrMVC.Models { public class ConstructionRepository { private CRDataContext db = new CRDataContext(); public IQueryable<MaterialsObj> FindAllMaterials() { var materials = from m in db.Materials join Mt in db.MeasurementTypes on m.MeasurementTypeId equals Mt.Id select new MaterialsObj() { Id = Convert.ToInt64(m.Mat_id), Mat_Name = m.Mat_Name, Mes_Name = Mt.Name, }; return materials; } } } And My MaterialsObj class is under CrMVC.BusinessObjects namespace and i using it in my repository class.... namespace CrMVC.BusinessObjects { public class MaterialsObj { //My logic here } } But when i compile this i get this error c:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files\root\19360d4c\3d21e226\App_Web_materials.aspx.7d2669f4.a8f-zsw5.0.cs(148): error CS0426: The type name 'Materials' does not exist in the type 'CrMVC.Models.ConstructionRepository' Am i missing something any suggestion.... Edit: There is no class named Materials in my repository class then why i get this error..

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• Best Practice - Removing item from generic collection in C#

  - by Matt Davis

  I'm using C# in Visual Studio 2008 with .NET 3.5. I have a generic dictionary that maps types of events to a generic list of subscribers. A subscriber can be subscribed to more than one event. private static Dictionary<EventType, List<ISubscriber>> _subscriptions; To remove a subscriber from the subscription list, I can use either of these two options. Option 1: ISubscriber subscriber; // defined elsewhere foreach (EventType event in _subscriptions.Keys) { if (_subscriptions[event].Contains(subscriber)) { _subscriptions[event].Remove(subscriber); } } Option 2: ISubscriber subscriber; // defined elsewhere foreach (EventType event in _subscriptions.Keys) { _subscriptions[event].Remove(subscriber); } I have two questions. First, notice that Option 1 checks for existence before removing the item, while Option 2 uses a brute force removal since Remove() does not throw an exception. Of these two, which is the preferred, "best-practice" way to do this? Second, is there another, "cleaner," more elegant way to do this, perhaps with a lambda expression or using a LINQ extension? I'm still getting acclimated to these two features. Thanks. EDIT Just to clarify, I realize that the choice between Options 1 and 2 is a choice of speed (Option 2) versus maintainability (Option 1). In this particular case, I'm not necessarily trying to optimize the code, although that is certainly a worthy consideration. What I'm trying to understand is if there is a generally well-established practice for doing this. If not, which option would you use in your own code?

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• DataTable vs. Collection in .Net

  - by B Pete

  I am writing a program that needs to read a set of records that describe the register map of a device I need to communicate with. Each record will have a handfull of fields that describe the properties of each register. I don't really need to edit or modify the data in my VB or C# program, though I would like to be able to display the data on a grid. I would like to store the data in a CSV file, or perhaps an XML file. I need to enable users to edit the data off-line, preferably in excel. I am considering using a DataTable or a Collection of "Register" objects (which I would define). I prototyped a DataTable, and found I can read/write XML easily using the built in methods and I can easily bind to a DataGridView. I was not able to find a way to retreive info on a single register without using a query that returns a collection of rows, even though I defined a unique primaty key column. The syntax to get a value from a column is also complex, though I could be missing something on both counts. I'm tempted to use a collection of "Register" objects that I can access via a unique key. It would be a little more coding up front, but seems like a cleaner solution overall. I should still be able to use LINQ to dataset to query subsets of registers when I need them, but would also be able to grab a single field using a the key value, something like this: Registers(keyValue).fieldName). Which would be a cleaner approach to the problem? Is there a way to read/write XML into a Collection without needing custom code? Could this be accomplished using String for a key?

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• Display gridview in new window

  - by Ricardo Deano

  Hello all. Just a bit of advice needed really in terms of how I should handle my current scenario: I have a web page that searches for products/category information the results of which are at present displayed in a gridview on the same page. However, said gridview is a bit of a beast and as such, I would like to have a page that the user searches for, a button is pressed and the subsequent gridview is displayed in a new window. Ultimately, I would like the user to be able to make multiple searches so that new windows can have multiple gridviews containing different data sets. My current thinking is to create session variables that can be pulled through onto 'the gridview page'. Having said that, I'm not sure that would work if multiple searches are created? I am also thinking I might be able to create said 'gridview window' using javascript but my concern here is the potential loss of functionality of the gridview i.e. paging, sorting, editing, etc. Does anyone have any thoughts or theories on this? What would be "best practise"? Any thoughts greatly appreciated and taken on board. PS: This is being developed in .net, using c# and LINQ. PPS: I'm a noob so be gentle!!

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• Hiding Command Prompt with CodeDomProvider

  - by j-t-s

  Hi All I've just got my own little custom c# compiler made, using the article from MSDN. But, when I create a new Windows Forms application using my sample compiler, the MSDOS window also appears, and if I close the DOS window, my WinForms app closes too. How can I tell the Compiler? not to show the MSDOS window at all? Thank you :) Here's my code: using System; namespace JTS { public class CSCompiler { protected string ot, rt, ss, es; protected bool rg, cg; public string Compile(String se, String fe, String[] rdas, String[] fs, Boolean rn) { System.CodeDom.Compiler.CodeDomProvider CODEPROV = System.CodeDom.Compiler.CodeDomProvider.CreateProvider("CSharp"); ot = fe; System.CodeDom.Compiler.CompilerParameters PARAMS = new System.CodeDom.Compiler.CompilerParameters(); // Ensure the compiler generates an EXE file, not a DLL. PARAMS.GenerateExecutable = true; PARAMS.OutputAssembly = ot; PARAMS.CompilerOptions = "/target:winexe"; PARAMS.ReferencedAssemblies.Add(typeof(System.Xml.Linq.Extensions).Assembly.Location); PARAMS.LinkedResources.Add("this.ico"); foreach (String ay in rdas) { if (ay.Contains(".dll")) PARAMS.ReferencedAssemblies.Add(ay); else { string refd = ay; refd = refd + ".dll"; PARAMS.ReferencedAssemblies.Add(refd); } } System.CodeDom.Compiler.CompilerResults rs = CODEPROV.CompileAssemblyFromFile(PARAMS, fs); if (rs.Errors.Count > 0) { foreach (System.CodeDom.Compiler.CompilerError COMERR in rs.Errors) { es = es + "Line number: " + COMERR.Line + ", Error number: " + COMERR.ErrorNumber + ", '" + COMERR.ErrorText + ";" + Environment.NewLine + Environment.NewLine; } } else { // Compilation succeeded. es = "Compilation Succeeded."; if (rn) System.Diagnostics.Process.Start(ot); } return es; } } }

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• Hiding Command Prompt with CodeDomProvider

  - by j-t-s

  Hi All I've just got my own little custom c# compiler made, using the article from MSDN. But, when I create a new Windows Forms application using my sample compiler, the MSDOS window also appears, and if I close the DOS window, my WinForms app closes too. How can I tell the Compiler? not to show the MSDOS window at all? Thank you :) Here's my code: using System; namespace JTS { public class CSCompiler { protected string ot, rt, ss, es; protected bool rg, cg; public string Compile(String se, String fe, String[] rdas, String[] fs, Boolean rn) { System.CodeDom.Compiler.CodeDomProvider CODEPROV = System.CodeDom.Compiler.CodeDomProvider.CreateProvider("CSharp"); ot = fe; System.CodeDom.Compiler.CompilerParameters PARAMS = new System.CodeDom.Compiler.CompilerParameters(); // Ensure the compiler generates an EXE file, not a DLL. PARAMS.GenerateExecutable = true; PARAMS.OutputAssembly = ot; PARAMS.CompilerOptions = "/target:winexe"; PARAMS.ReferencedAssemblies.Add(typeof(System.Xml.Linq.Extensions).Assembly.Location); PARAMS.LinkedResources.Add("this.ico"); foreach (String ay in rdas) { if (ay.Contains(".dll")) PARAMS.ReferencedAssemblies.Add(ay); else { string refd = ay; refd = refd + ".dll"; PARAMS.ReferencedAssemblies.Add(refd); } } System.CodeDom.Compiler.CompilerResults rs = CODEPROV.CompileAssemblyFromFile(PARAMS, fs); if (rs.Errors.Count > 0) { foreach (System.CodeDom.Compiler.CompilerError COMERR in rs.Errors) { es = es + "Line number: " + COMERR.Line + ", Error number: " + COMERR.ErrorNumber + ", '" + COMERR.ErrorText + ";" + Environment.NewLine + Environment.NewLine; } } else { // Compilation succeeded. es = "Compilation Succeeded."; if (rn) System.Diagnostics.Process.Start(ot); } return es; } } }

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