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• How to replace for-loops with a functional statement in C#?

  - by Lernkurve

  A colleague once said that God is killing a kitten every time I write a for-loop. When asked how to avoid for-loops, his answer was to use a functional language. However, if you are stuck with a non-functional language, say C#, what techniques are there to avoid for-loops or to get rid of them by refactoring? With lambda expressions and LINQ perhaps? If so, how? Questions So the question boils down to: Why are for-loops bad? Or, in what context are for-loops to avoid and why? Can you provide C# code examples of how it looks before, i.e. with a loop, and afterwards without a loop?

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• Microsoft SQL Server 2008 - 99% fragmentation on non-clustered, non-unique index

  - by user550441

  I have a table with several indexes (defined below). One of the indexes (IX_external_guid_3) has 99% fragmentation regardless of rebuilding/reorganizing the index. Anyone have any idea as to what might cause this, or the best way to fix it? We are using Entity Framework 4.0 to query this, the EF queries on the other indexed fields about 10x faster on average then the external_guid_3 field, however an ADO.Net query is roughly the same speed on both (though 2x slower than the EF Query to indexed fields). Table id(PK, int, not null) guid(uniqueidentifier, null, rowguid) external_guid_1(uniqueidentifier, not null) external_guid_2(uniqueidentifier, null) state(varchar(32), null) value(varchar(max), null) infoset(XML(.), null) -- usually 2-4K created_time(datetime, null) updated_time(datetime, null) external_guid_3(uniqueidentifier, not null) FK_id(FK, int, null) locking_guid(uniqueidentifer, null) locked_time(datetime, null) external_guid_4(uniqueidentifier, null) corrected_time(datetime, null) is_add(bit, not null) score(int, null) row_version(timestamp, null) Indexes PK_table(Clustered) IX_created_time(Non-Unique, Non-Clustered) IX_external_guid_1(Non-Unique, Non-Clustered) IX_guid(Non-Unique, Non-Clustered) IX_external_guid_3(Non-Unique, Non-Clustered) IX_state(Non-Unique, Non-Clustered)

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• How to return arrays with the biggest elements in C#?

  - by theateist

  I have multiple int arrays: 1) [1 , 202,4 ,55] 2) [40, 7] 3) [2 , 48 ,5] 4) [40, 8 ,90] I need to get the array that has the biggest numbers in all positions. In my case that would be array #4. Explanation: arrays #2, #4 have the biggest number in 1st position, so after the first iteration these 2 arrays will be returned ([40, 7] and [40, 8 ,90]) now after comparing 2nd position of the returned array from previous iteration we will get array #4 because 8 7 and so on... Can you suggest an efficient algorithm for this? Doing with Linq will be preferable. UPDATE There is no limitation for the length, but as soon as some number in any position is greater, so this array is the biggest.

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• First try StructureMap and MVC3 via NuGet

  - by Angel Escobedo

  Hello Guys, I'm trying to figure how to config StructureMap for ASP.NET MVC3 I've already using NuGet and I notice that it creates App_Start Folder with a cs file named as StructuremapMVC, so I check it and notice that is the same code but simplified that will be written manually on App_Start section placed on Global.asax... My Question is when I inject some IoC on my Controllers as the follow (I use this pattern : Entity Framework 4 CTP 4 / CTP 5 Generic Repository Pattern and Unit Testable) : private readonly IAsambleaRepository _aRep; private readonly IUnitOfWork _uOw; public AsambleaController(IAsambleaRepository aRep, IUnitOfWork uOw) { _aRep = aRep; this._uOw = uOw; } public ActionResult List(string period) { var rs = _aRep.ByPeriodo(period).ToList<Asamblea>(); return View(); } I got an Exception Exception Details: System.MissingMethodException: No parameterless constructor defined for this object.

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• Calculating holidays

  - by Ralph Shillington

  A number of holidays move around from year to year. For example, in Canada Victoria day (aka the May two-four weekend) is the Monday before May 25th, or Thanksgiving is the 2nd Monday of October (in Canada). I've been using variations on this Linq query to get the date of a holiday for a given year: var year = 2011; var month = 10; var dow = DayOfWeek.Monday; var instance = 2; var day = (from d in Enumerable.Range(1,DateTime.DaysInMonth(year,month)) let sample = new DateTime(year,month,d) where sample.DayOfWeek == dow select sample).Skip(instance-1).Take(1); While this works, and is easy enough to understand, I can imagine there is a more elegant way of making this calculation versus this brute force approach. Of course this doesn't touch on holidays such as Easter and the many other lunar based dates.

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• SQL Server 2008 GUID column is all 0's

  - by Andy Evans

  I'm hoping this is a simple goof I did on my end ... I have a table in my database set up like so: column name: widget_guid data type: uniqueidentifier allow nulls: false default value: newid() identity: false row guid: true When records are created (via LINQ to SQL) that the values in this field are formatted as a GUID but contain all 0's My assumption was that when a new record was created, that a guid would be autogenerated for that column, much like an auto-incrementing row id. Is this not true? Any help would be greatly appreciated. Thanks.

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• Using VirtualMode on a DataGridView when the number of rows/columns isn't known

  - by Nathan Baulch

  I need to display an unknown length sequence of dictionaries with unknown keys efficiently in a data grid. This sequence is the result of a potentially slow LINQ query that could contain any number of results. At first I thought that VirtualMode on DataGridView was what I was looking for but it appears that the number of rows and columns must be known upfront. I tried adding a single row and column then adding more as needed from the CellValueNeeded event but this doesn't work. Is this even possible with VirtualMode? Or do I need to estimate how many rows are visible on the screen and manually build up the rows/columns? And if so, how do I ensure that a vertical scrollbar is present and react appropriately when a user uses it?

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• Comparing 2 objects and retrive a list of fields with different values

  - by ajj

  Hi given a class with 35 fields and 2 objects with a certain number of different fields value. is there an clever way to get a list with the fields name where the objext Say obj1.Name = "aaa"; obj1.LastName = "bbb"; obj1.Address = "xcs"; obj2.Name = "aaa"; obj2.LastName = "ccc"; obj2.Address = "jk"; objective: list containing 2 strings LastName and Address I see reflection as the way to go but with 35 fields I am afraid it s to heavy. Any other idea, like linq? Thanks, a.

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• LINQ2SQL: how to merge two columns from the same table into a single list

  - by TomL

  this is probably a simple question, but I'm only a beginner so... Suppose I have a table containing home-work locations (cities) certain people use. Something like: ID(int), namePerson(string), homeLocation(string), workLocation(string) where homeLocation and workLocation can both be null. Now I want all the different locations that are used merged into a single list. Something like: var homeLocation = from hm in Places where hm.Home != null select hm.Home; var workLocation = from wk in Places where wk.Work != null select wk.Work; List<string> locationList = new List<string>(); locationList = homeLocation.Distinct().ToList<string>(); locationList.AddRange(workLocation.Distinct().ToList<string>()); (which I guess would still allow duplicates if they have the same value in both columns, which I don't really want...) My question: how this be put into a single LINQ statement? Thanks in advance for your help!

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• How to implement multi relationship in SQL Server?

  - by Ethan

  I’m trying to design a database to use with ASP.net MVC application. Here is the scenario: There are three entities and users can post their comments for each of these different entities. I just wonder how just put one table for Comments and link all other entities to it. Obviously, Comments table needs 3 references (foreign key) to those tables but as you know these foreign keys can’t be null and just one of them can be filled for each row. Is there any better way than implementing three different tables for each entity’s comments?

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• How extension methods work in background ?

  - by Freshblood

  I am just cuirous about behind of extension method mechanism.Some questions and answer appear in my mind. MyClass.OrderBy(x=>x.a).OrderBy(x=>x.b); I was guessing that mechanism was first orderby method works and order them by a member then returns sorted items in IEnumarable interface then next Orderby method of IEnumarable Order them for b paramater.But i am wrong when i look at this linq query. MyClass.Orderby(x=>x.a).ThenOrderBy(x=>x.b); this is slightly different and tells me that i am wrong.Because this is not ordering by a then b and not possible to have such result if i was right.This get me confuse enough... Similiar structure is possible to write withot extension methods as first query but second is not possible.This prove i am wrong . Can u explain it ?

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• Manipulating individual rows of a datagrid

  - by pfranchise

  Hey, recently I started working on a webpage that has a datagrid. I understand how to add datasources and that sort of thing, or at least I am starting to get it. But my question is about manipulating individual rows or cells. Is that only possible during the databind event handler, that is the only place I have been able to do it so far. I am sure there is a more abstract way of doing the things I want to do, but there are times where I just want to say Datagrid.add(row). I mean, if the datagrid is made up of a certain object type, can I make a new object of that type and just chuck it on the end? I am still new to this stuff, so perhaps what I want to do would defeat the purpose of this added abstraction, but figured I would ask around. Thanks for any advice, tips, or tricks people feel like sharing. Edit: for clarification I am using c#, entity framework, asp.net, and an SQL database.

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• Please help me translate C# code to Ruby

  - by Valentin Vasilyev

  Here is the code: using System; using System.Collections.Generic; using System.Linq; namespace cs2 { class Program { static void Main(string[] args) { var i=Fibs.TakeWhile(x=>x < 1000).Where(x=>x % 2==0).Sum(); } static IEnumerable<long> Fibs() { long a = 0, b = 1; while (true) { yield return b; b += a; a = b - a; } } } }

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• What is my problem with ASP.NET pubslishing?

  - by Shankarooni

  I am done testing my site and I want to upload it to a site like this http://www.university.edu/mydepartment/myname the admin told me the server runs on .NET 3.5. So i used Linq ... now i tried to upload the site by two ways: when i just copy everything (with modification of web.config database settings) i get an error: CS0246: The type or namespace name 'DataClassesDataContext' could not be found (are you missing a using directive or an assembly reference?) Version Information: Microsoft .NET Framework Version:2.0.50727.3082; ASP.NET Version:2.0.50727.3082 Note here it says version 2.0 did he just lie to me? or its my configuration mistake? anyway, i added the reference, nothing changes. I tried also publishing (Build, publish) with option to keep the pre-comiled site updatable, and I get one line saying: this is a makefile and should be deleted! what is going on?

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• Architecture Guidance for designing Workflow Foundation with WCF

  - by Matrix

  We are planning to use WF 3.5 with WCF 3.5 and Entity Framework 1.0 for the upcoming major project. I'm looking for guidance on the architecture side. This new application will be based on typical 3-tier architecture as depicted below: Presentation Tier: ASP.NET Web Forms 3.5 Business Tier: WF 3.5 + BLL's that expose the business logic through WCF service interfaces (using EF for Data Access) Data Tier: SQL Server 2000 Here are the questions: Though the Workflow Foundation has Workflow Services, where we can map the WCF service contracts to a workflow, is this the right way to design the applications? Is EF 1.0 business entities can be used in n-tier apps without sacrificing the tracking changes in the entities? Is there a sample reference application available to look? Thanks.

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• Auto-generated values for columns in database

  - by Jamal

  Is it a good practice to initialize columns that we can know their values in database, for example identity columns of type unique identifier can have a default value (NEWID()), or columns that shows the record create date can have a default value (GETDATE()). Should I go through all my tables and do this whereever I am sure that I won't need to assign the value manually and the Auto-generated value is correct. I am also thinking about using linq-to-sql classes and setting the "Auto Generated Value" property of these columns to true. Maybe this is what everybody already knows or maybe I am asking a question about a fundamental issue, if so please tell me.

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• EntityFramework & RowNumber

  - by Dan

  Hello. How can I query RowNumber with Entity Framework? For example: var result = data.Users .OrderByDescending("Birthday") .ThenBy("LastName") .ThenBy("FirstName") .Select(u => { RowNumber = ???, u.FirstName, u.LastName }); I want to implement paging for my grid, but I cannot solve problem with finding page with needed user. I'm using EF4.0. Select method with index(http://msdn.microsoft.com/en-us/vcsharp/aa336758.aspx#SelectIndexed) not works with EF. May be there is another way to implement this?

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• Why MSSQL keeps throwing me Exceptions?

  - by Augusto Càzares

  I have my project in .NET that uses a db in MSSQL Server,i'm using LINQ , sometimes when the projec throws me an exception (Constraint) in a part of the project this same error keeps showing in other part of the project when i do another thing with the db, like when i do an insertion and i had before an exception on delete the insertion throws me the delete exeption, and it remainds this way until i close and open again the project, my major problem is when this happen in my online project, this error in my project causes me problems in the project i'm testing online (i use the same db). I don't know if this exception is on the memory or something but its have been causing me a lot of headechs.

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• Excel XML Newline in Cell

  - by spasarto

  I am using LINQ to XML to create an Excel XML file. I want to include newlines within the cells. Excel uses the &#10; literal to represent a new line. If I try to add this using an XText: XText newlineElement = new XText( "Foo&#10;Bar" ); I get: Foo&amp;#10;Bar Which shows up in Excel as: Foo&#10;Bar Is there a way to write &#10 to the XML file without doing a String.Replace( "&amp;#10;", "&#10;" ) over the resulting file text?

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• What is your favorite way to read XML files?

  - by stacker

  Let's take this xml structure as example: <?xml version="1.0" encoding="utf-8"?> <Configuration-content> <XFile Name="file name 1" /> <XFile Name="name2" /> <XFile Name="name3" /> <XFile Name="name4" /> </Configuration-content> C# interface to implement: public class Configuration { public XFile[] Files { get; set; } } public interface IConfigurationRipository { Configuration Get(); void Save(Configuration entity); } I wonder what's the best way to do that. The task is to implement IConfigurationRipository using your favorite approach.

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• iPhone - Create non-persistent entities in core data

  - by ncohen

  Hi everyone, I would like to use entity objects but not store them... I read that I could create them like this: myElement = (Element *)[NSEntityDescription insertNewObjectForEntityForName:@"Element" inManagedObjectContext:managedObjectContext]; And right after that remove them: [managedObjectContext deleteObject:myElement]; then I can use my elements: myElement.property1 = @"Hello"; This works pretty well even though I think this is probably not the most optimal way to do it... Then I try to use it in my UITableView... the problem is that the object get released after the initialization. My table becomes empty when I move it! Thanks edit: I've also tried to copy the element ([myElement copy]) but I get an error...

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• Using multiple databases within one application

  - by Alex

  I have a web application made for several groups of people not connected with each other. Instead of using one database for all of them, I'm thinking about making separate databases. This will improve the speed of the queries and make me free from checking to what group the user belongs. But since I'm working with LINQ to SQL, my classes are explicitly connected with the databases, so I will have to make separate DataContexts for all of the databases. So how can I solve this problem? Or should I just not bother and use one database only?

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• How to properly reserve identity values for usage in a database?

  - by esac

  We have some code in which we need to maintain our own identity (PK) column in SQL. We have a table in which we bulk insert data, but we add data to related tables before the bulk insert is done, thus we can not use an IDENTITY column and find out the value up front. The current code is selecting the MAX value of the field and incrementing it by 1. Although there is a highly unlikely chance that two instances of our application will be running at the same time, it is still not thread-safe (not to mention that it goes to the database everytime). I am using the ADO.net entity model. How would I go about 'reserving' a range of id's to use, and when that range runs out, grab a new block to use, and guarantee that the same range will not be used.

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• Is EF4 "Code Only" ready for production use?

  - by Tommy Jakobsen

  I've been looking at the new Entity Framework 4 Code Only features, and I really like them. But I'm having a hard time finding good resource on the feature. Everything seems to be spread around blongs here and there, so this make me wonder if it's ready to be used for a serious project? What do you think? Is it ready for production use or should I use the more traditional approach (EDMX designer, POCO objects)? Also, I would like to know if there are any features that Code Only does not support yet, compared to the EDMX designer? What do you think about the Code Only feature? Is it "mature" yet? Thank you.

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• How to unit test generic classes

  - by Rowland Shaw

  I'm trying to set up some unit tests for an existing compact framework class library. However, I've fallen at the first hurdle, where it appears that the test framework is unable to load the types involved (even though they're both in the class library being tested) Test method MyLibrary.Tests.MyGenericClassTest.MyMethodTest threw exception: System.MissingMethodException: Could not load type 'MyLibrary.MyType' from assembly 'MyLibrary, Version=1.0.3778.36113, Culture=neutral, PublicKeyToken=null'.. My code is loosely: public class MyGenericClass<T> : List<T> where T : MyType, new() { public bool MyMethod(T foo) { throw new NotImplementedException(); } } With test methods: public void MyMethodTestHelper<T>() where T : MyType, new() { MyGenericClass<T> target = new MyGenericClass<T>(); foo = new T(); expected = true; actual = target.MyMethod(foo); Assert.AreEqual(expected, actual); } [TestMethod()] public void MyMethodTest() { MyMethodTestHelper<MyType>(); } I'm a bit stumped though, as I can't even get it to break in the debugger to get to the inner exception, so what else do I check? EDIT this does seem to be something specific to the Compact Framework - recompiling the class libraries and the unit tests for the full framework, gives the expected output (i.e. the debugger stops when I'm going to throw a NotImplementedException).

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