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  • How does OfType<T>() Work?

    - by TheCloudlessSky
    How does OfType() Work? I read this link about what's going on but how exactly does the LINQ provider know how to get all objects matching the specified type. I know the IQueryable<T> "chains" up requests and then evaluates when GetEnumerator() is called (right?). Specifically I want to know how does the framework quickly do type comparison? I wrote a method in a .NET 2.0 project that went like this (since 2.0 doesn't support these kind of features): public IEnumerable<TResult> OfType<TResult>() where TResult : class { foreach (TItem item in this.InnerList) { TResult matchItem = item as TResult; if (matchItem != null) { yield return matchItem; } } } Is this the best implementation?

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  • List.clear() followed by List.add() not working.

    - by Vincent
    I have the following C# Class/Function: class Hand { private List<Card> myCards = new List<Card>(); public void sortBySuitValue() { IEnumerable<Card> query = from s in myCards orderby (int)s.suit, (int)s.value select s; myCards = new List<Card>(); myCards.AddRange(query); } } On a card Game. This works fine, however, I had trouble at first, instead of using myCards = new List(); to 'reset' myCards, I would use myCards.clear(), however, once I called the clear function, I would not be able to call myCards.add() or myCards.addRange(). The count would stay at zero. Is my current approach good? Is using LINQ to sort my cards good/bad?

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  • Using Large Arrays in VB.NET

    - by Tim
    I want to extract large amounts of data from Excel, manipulate it and put it back. I have found the best way to do this is to extract the data from an Excel Range in to a large array, change the contents on the array and write it back to the Excel Range. I am now rewriting the application using VB.NET 2008/2010 and wish to take advantage of any new features. Currently I have to loop through the contents of the array to find elements with certain values; also sorting large arrays is cumbersome. I am looking to use the new features, including LINQ to manipulate the data in my array. Does anybody have any advice on the easiest ways to filter / query, sort etc. data in a large array. Also what are the reasonable limits to the size of the array? ~Many Thanks

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  • Any Way to Use a Join in a Lambda Where() on a Table<>?

    - by lush
    I'm in my first couple of days using Linq in C#, and I'm curious to know if there is a more concise way of writing the following. MyEntities db = new MyEntities(ConnString); var q = from a in db.TableA join b in db.TableB on a.SomeFieldID equals b.SomeFieldID where (a.UserID == CurrentUser && b.MyField == Convert.ToInt32(MyDropDownList.SelectedValue)) select new { a, b }; if(q.Any()) { //snip } I know that if I were to want to check the existence of a value in the field of a single table, I could just use the following: if(db.TableA.Where(u => u.UserID == CurrentUser).Any()) { //snip } But I'm curious to know if there is a way to do the lambda technique, but where it would satisfy the first technique's conditions across those two tables. Sorry for any mistakes or clarity, I'll edit as necessary. Thanks in advance.

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  • Check If Stored Procedure Returns Value

    - by Eric
    Hello all, I am using Linq 2 Sql in VS 2010, and I have the following stored procedure to check a username and password ALTER PROCEDURE dbo.CheckUser ( @username varchar(50), @password varchar(50) ) AS SELECT * FROM Users Where UserName=@username AND Password=@password The problem I'm having is that it throws an exception if the username and password are incorrect. I'd like to perform a check to see if there is a return value, rather than using try/catch to determine whether the procedure returned a value. Should I do this check in code (C#)? Or is there a way to do it in SQL? Thanks.

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  • Why does do this code do if(sz !=sz2) sz = sz2 !?!

    - by acidzombie24
    For the first time i created a linq to sql classes. I decided to look at the class and found this. What... why is it doing if(sz !=sz2) { sz = sz2; }. I dont understand. Why isnt the set generated as this._Property1 = value? private string _Property1; [Column(Storage="_Property1", CanBeNull=false)] public string Property1 { get { return this._Property1; } set { if ((this._Property1 != value)) { this._Property1 = value; } } }

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  • ReSharper 5.0s LINQ Refactoring Continues to be Amazing!

    In this post, well take a straight forward procedure based set of code and convert it to LINQ using a ReSharper from JetBrains suggestion.   Ive found that in general, when I do things with foreach syntax, there is often a better way in Linq to do this.  The better does not jump out [...]...Did 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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  • Fin de LINQ to HPC : Microsoft abandonne sa plateforme de traitement de gros volumes de données pour son concurrent Hadoop

    Fin de LINQ to HPC : Microsoft abandonne sa plateforme de traitement de gros volumes de données pour se concentrer sur le support de son concurrent Hadoop Microsoft abandonne LINQ to HPC (High performance computing), nom de code Dryad, sa propre plateforme haute performance pour des calculs distribués et la gestion intensive des données, pour se concentrer sur le support de son concurrent Hadoop dans ses produits. L'éditeur avait récemment manifesté son intérêt pour la plateforme Java de stockage et de traitement par lot de très grandes quantités de données (Big Data) Hadoop, en publiant notamment deux connecteurs

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  • sharp architecture, FluentNHibernate, automapper, DTO, 1:m persistence question

    - by csetzkorn
    Let us say we have a class A which has a reference to another class B (1:m) public class A { public virtual B B { get; set; } } I reflect this using FluentNHibernate within the sharp architecture and also manage to ‘initialise’ A and its B via a DTO and Automapper. The DTO contain A’s values and B (just B’s id value/A’s foreign key initialised). I was hoping that I can persist A by ‘just’ using its 'out of the box repository' without requiring B’s repository using: SaveOrUpdate(A); (A has been mapped using AutoMapper and contains B with its Id initialised) Was my assumption too naive? Can I achieve this somehow (without ever requiring B’s repository)? Or do I have to use A’s and B’s repository in, for example, the controller or some other service layer? Thanks. Best wishes, Christian

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  • HiLo vs Identity?

    - by Mendy
    This is the same question as: http://stackoverflow.com/questions/803872/hilo-or-identity Let's take the database of this site as an example. Lets say that the site has the following tables: Posts. Votes. Comments. What is the best strategy to use for it: Identity - which is more common. OR HiLo - which give best performance. Edit: if HiLo is the best, how the structure of the DB would be?

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  • Benchmark Linq2SQL, Subsonic2, Subsonic3 - Any other ideas to make them faster ?

    - by Aristos
    I am working with Subsonic 2 more than 3 years now... After Linq appears and then Subsonic 3, I start thinking about moving to the new Linq futures that are connected to sql. I must say that I start move and port my subsonic 2 with SubSonic 3, and very soon I discover that the speed was so slow thats I didn't believe it - and starts all that tests. Then I test Linq2Sql and see also a delay - compare it with Subsonic 2. My question here is, especial for the linq2sql, and the up-coming dotnet version 4, what else can I do to speed it up ? What else on linq2sql settings, or classes, not on this code that I have used for my messures I place here the project that I make the tests, also the screen shots of the results. How I make the tests - and the accurate of my measures. I use only for my question Google chrome, because its difficult for me to show here a lot of other measures that I have done with more complex programs. This is the most simple one, I just measure the Data Read. How can I prove that. I make a simple Thread.Sleep(10 seconds) and see if I see that 10 seconds on Google Chrome Measure, and yes I see it. here are more test with this Sleep thead to see whats actually Chrome gives. 10 seconds delay 100 ms delay Zero delay There is only a small 15ms thats get on messure, is so small compare it with the rest of my tests that I do not care about. So what I measure I measure just the data read via each method - did not count the data or database delay, or any disk read or anything like that. Later on the image with the result I show that no disk activity exist on the measures See this image to see what really I measure and if this is correct Why I chose this kind of test Its simple, it's real, and it's near my real problem that I found the delay of subsonic 3 in real program with real data. Now lets tests the dals Start by see this image I have 4-5 calls on every method, the one after the other. The results are. For a loop of 100 times, ask for 5 Rows, one not exist, approximatively.. Simple adonet:81ms SubSonic 2 :210ms linq2sql :1.70sec linq2sql using CompiledQuery.Compile :239ms Subsonic 3 :15.00sec (wow - extreme slow) The project http://www.planethost.gr/DalSpeedTests.rar Can any one confirm this benchmark, or make any optimizations to help me out ? Other tests Some one publish here this link http://ormbattle.net/ (and then remove it - don not know why) In this page you can find a really useful advanced tests for all, except subsonic 2 and subsonic 3 that I have here ! Optimizing What I really ask here is if some one can now any trick how to optimize the DALs, not by changing the test code, but by changing the code and the settings on each dal. For example... Optimizing Linq2SQL I start search how to optimize Linq2sql and found this article, and maybe more exist. Finally I make the tricks from that page to run, and optimize the code using them all. The speed was near 1.50sec from 1.70.... big improvement, but still slow. Then I found a different way - same idea article, and wow ! the speed is blow up. Using this trick with CompiledQuery.Compile, the time from 1.5sec is now 239ms. Here is the code for the precompiled... Func<DataClassesDataContext, int, IQueryable<Product>> compiledQuery = CompiledQuery.Compile((DataClassesDataContext meta, int IdToFind) => (from myData in meta.Products where myData.ProductID.Equals(IdToFind) select myData)); StringBuilder Test = new StringBuilder(); int[] MiaSeira = { 5, 6, 10, 100, 7 }; using (DataClassesDataContext context = new DataClassesDataContext()) { context.ObjectTrackingEnabled = false; for (int i = 0; i < 100; i++) { foreach (int EnaID in MiaSeira) { var oFindThat2P = compiledQuery(context, EnaID); foreach (Product One in oFindThat2P) { Test.Append("<br />"); Test.Append(One.ProductName); } } } } Optimizing SubSonic 3 and problems I make many performance profiling, and start change the one after the other and the speed is better but still too slow. I post them on subsonic group but they ignore the problem, they say that everything is fast... Here is some capture of my profiling and delay points inside subsonic source code I have end up that subsonic3 make more call on the structure of the database rather than on data itself. Needs to reconsider the hole way of asking for data, and follow the subsonic2 idea if this is possible. Try to make precompile to subsonic 3 like I did in linq2Sql but fail for the moment... Optimizing SubSonic 2 After I discover that subsonic 3 is extreme slow, I start my checks on subsonic 2 - that I have never done before believing that is fast. (and it is) So its come up with some points that can be faster. For example there are many loops like this ones that actually is slow because of string manipulation and compares inside the loop. I must say to you that this code called million of times ! on a period of few minutes ! of data asking from the program. On small amount of tables and small fields maybe this is not a big think for some people, but on large amount of tables, the delay is even more. So I decide and optimize the subsonic 2 by my self, by replacing the string compares, with number compares! Simple. I do that almost on every point that profiler say that is slow. I change also all small points that can be even a little faster, and disable some not so used thinks. The results, 5% faster on NorthWind database, near 20% faster on my database with 250 tables. That is count with 500ms less in 10 seconds process on northwind, 100ms faster on my database on 500ms process time. I do not have captures to show you for that because I have made them with different code, different time, and track them down on paper. Anyway this is my story and my question on all that, what else do you know to make them even faster... For this measures I have use Subsonic 2.2 optimized by me, Subsonic 3.0.0.3 a little optimized by me, and Dot.Net 3.5

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  • How to retrieve row count of one-to-many relation while also including original entity?

    - by kaa
    Say I have two entities Foo and Bar where Foo has-many Bar's, class Foo { int ImportantNumber { get; set; } IEnumerable<Bar> Bars { get; set; } } class FooDTO { Foo Foo { get; set; } int BarCount { get; set; } } How can I efficiently sum up the number of Bars per Foo in a DTO using a single query, preferrably only with the Criteria interface. I have tried any number of ways to get the original entity out of a query with ´SetProjection´ but no luck. The current theory is to do something like SELECT Foo.*, BarCounts.counts FROM Foo LEFT JOIN ( SELECT fooId, COUNT(*) as counts FROM Bar GROUP BY fooId ) AS BarCounts ON Foo.id=BarCounts.fooId but with Criterias, and I just can't seem to figure out how.

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  • POJOs for Composite Primary Key from Foreign Key

    - by Gaurav
    hi, I have table in database that has only two columns and these two colums are FK references. they have made these two colums as composite primarykey. table structure Table A [ A_id PK Description ] Table B [ B_Id PK Description ] Table A_B_Pemissiom [ A_id (FK table A) B_Id (FK table B) PrimaryKey ( A_id,B_Id ) ] Can anyone help , I tried several ways and none of them works. Can anyone tell a working Hibernate mapping solution using annotations ? Thanks, Gaurav

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  • for my project I have problem in report

    - by pink rose
    public class stack { private int Array[]; private int top = -1; public int size; public stack(int size) { this.size=size; Array = new int[size]; } public void push(int j) { if (top < size) { Array[++top] = j; } } public int pop() { return Array[top--]; } public int top() { return Array[top]; } public boolean isEmpty() { return (top == -1); } } import javax.swing.JOptionPane; public class menu { private static stack s; private static int numbers[]; public static void main(String args[]) { start(); } public static void start() { int i = Integer.parseInt(JOptionPane.showInputDialog("1. size of array\n2. data entry\n3. display content\n4. exit")); switch (i) { case 1: setSize(); break; case 2: addElement(); break; case 3: showElements(); break; case 4: exit(); } } public static void setSize() { int size = Integer.parseInt(JOptionPane.showInputDialog("Please Enter The Size")); s = new stack(size); numbers = new int[10]; start(); } public static void addElement() { for(int x=0;x<s.size;x++) { int e = Integer.parseInt(JOptionPane.showInputDialog("Please Enter The Element")); numbers[e]++; s.push(e); } start(); } public static void showElements() { String result = ""; int temp; while (!s.isEmpty()) { temp = s.pop(); if (numbers[temp] == 1) { result = temp+result; } } JOptionPane.showMessageDialog(null, result); start(); } public static void exit() { System.exit(0); } } This my project I was finished but I have problem in question in my report Conclusion. It should summarize the state of your project and indicate which part of your project is working and which part is not working or with limitations. You may also provide your suggestions and comments to this project what I can answer I didn't have any idea

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  • Order by null/not null with ICriteria

    - by Kristoffer
    I'd like to sort my result like this: First I want all rows/objects where a column/property is not null, then all where the colmn/property is null. Then I want to sort by another column/property. How can I do this with ICriteria? Do I have to create my own Order class, or can it be done with existing code? ICriteria criteria = Session.CreateCriteria<MyClass>() .AddOrder(Order.Desc("NullableProperty")) // What do I do here? IProjection? Custom Order class? .AddOrder(Order.Asc("OtherProperty"));

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  • Fine tune some SQL called multiple times

    - by Carl
    Hi all, I currently have an SQL query which is currently called multiple times like this (pseudo code): foreach(KeyValuePair kvp in someMapList) { select col1 from table where col2 = kvp.key and col3 = kvp.value; //do some processing on the returned value } The above could obviously call the database a large number of times if it is a big list of pairs. Can anyone think of a more efficient piece of SQL which could essentially return a list of specific values based on a list of two unique pieces of information so that the processing can be done in bulk? One obvious one would be to build up a big piece of SQL with ORs but this would probably be quite inefficient? Thanks Carl

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  • ISQLQuery using AddJoin not loading related instance

    - by Remi Despres-Smyth
    I've got a problem using an ISQLQuery with an AddJoin. The entity I'm trying to return is RegionalFees, which has a composite-id which includes a Province instance. (This is the the instance being improperly loaded.) Here's the mapping: <class name="Project.RegionalFees, Project" table="tblRegionalFees"> <composite-id name="Id" class="Project.RegionalFeesId, project" unsaved-value="any" access="property"> <key-many-to-one class="Project.Province, Project" name="Region" access="property" column="provinceId" not-found="exception" /> <key-property name="StartDate" access="property" column="startDate" type="DateTime" /> </composite-id> <property name="SomeFee" column="someFee" type="Decimal" /> <property name="SomeOtherFee" column="someOtherFee" type="Decimal" /> <!-- Other unrelated stuff --> </class> <class name="Project.Province, Project" table="trefProvince" mutable="false"> <id name="Id" column="provinceId" type="Int64" unsaved-value="0"> <generator class="identity" /> </id> <property name="Code" column="code" access="nosetter.pascalcase-m-underscore" /> <property name="Label" column="label" access="nosetter.pascalcase-m-underscore" /> </class> Here's my query method: public IEnumerable<RegionalFees> GetRegionalFees() { // Using an ISQLQuery cause there doesn't appear to be an equivalent of // the SQL HAVING clause, which would be optimal for loading this set const String qryStr = "SELECT * " + "FROM tblRegionalFees INNER JOIN trefProvince " + "ON tblRegionalFees.provinceId=trefProvince.provinceId " + "WHERE EXISTS ( " + "SELECT provinceId, MAX(startDate) AS MostRecentFeesDate " + "FROM tblRegionalFees InnerRF " + "WHERE tblRegionalFees.provinceId=InnerRF.provinceId " + "AND startDate <= ? " + "GROUP BY provinceId " + "HAVING tblRegionalFees.startDate=MAX(startDate))"; var qry = NHibernateSessionManager.Instance.GetSession().CreateSQLQuery(qryStr); qry.SetDateTime(0, DateTime.Now); qry.AddEntity("RegFees", typeof(RegionalFees)); qry.AddJoin("Region", "RegFees.Id.Region"); return qry.List<RegionalFees>(); } The odd behavior here is that when I call GetRegionalFees (whose goal is to load just the most recent fee instances per region), it all loads fine if the Province instance is a proxy. If, however, Province is not loaded as a transparent proxy, the Province instance which is part of RegionalFees' RegionalFeesId property has null Code and Region values, although the Id value is set correctly. It looks to me like I have a problem in how I'm joining the Province class - since if it's lazy loaded the id is set from tblRegionalFees, and it gets loaded independently afterwards - but I haven't been able to figure out the solution.

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  • An item with the same key has already been added.

    - by senzacionale
    Can someone advice me how to prevent this error. An item with the same key has already been added.? // Failed to find a matching SessionFactory so make a new one. if (sessionFactory == null) { Check.Require(File.Exists(sessionFactoryConfigPath), "The config file at '" + sessionFactoryConfigPath + "' could not be found"); Configuration cfg = new Configuration(); cfg.Configure(sessionFactoryConfigPath); /*MINE*/ var persistenceModel = new PersistenceModel(); persistenceModel.AddMappingsFromAssembly(Assembly.Load("EMedicine.Core")); persistenceModel.Configure(cfg); /*END_OF_MINE*/ // Now that we have our Configuration object, create a new SessionFactory sessionFactory = cfg.BuildSessionFactory(); if (sessionFactory == null) { throw new InvalidOperationException("cfg.BuildSessionFactory() returned null."); } if (sessionFactoryConfigPath != null) sessionFactories.Add(sessionFactoryConfigPath, sessionFactory); } Error is here: sessionFactory = cfg.BuildSessionFactory();

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  • Spring HibernateTemplate: how it deals with transactions?

    - by EugeneP
    Could you explain, what happens behind the scene? Transaction management when using this template in Spring is absolutely unclear. What if I invoke 10 DAO methods that all use the same Hibernatetemplate and I invoke them one after another? Every method runs within its own transaction? It's not effective is not it?

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  • Castle ActiveRecord optimistic locking on properties

    - by Daniel T.
    Can Castle ActiveRecord do optimistic locking on properties? I found optimistic locking for the entire class, but not for an individual property. In my case, I need to make it so that adding/removing elements in a collection does not update the version number of the entity (so for example, adding a Product to a Store without changing any of Store's properties will not increment the version number).

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  • similarity match

    - by csetzkorn
    Many search engine have the 'did you mean' functionality. Is there a simple way to use (N)Hibernate (e.g. ICriteria) to find an entity (e.g. keyword) based on similarity. Please note that I do not mean Expression.Like or something like this. I hope this question makes sense. Thanks. Christian

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  • How to map IEnumerable<SelectListItem> to IList<> for ListBox

    - by Superhuman
    I have two classes. Class1 and Class2. public class Class1{ ... public virtual IList<Class2> Class2s{get;set;} ... } public class Class2{ ... public virtual IList<Class1> Class1s{get;set;} ... } The view contains <%=Html.ListBox("Class2s", ViewData.Model.Class2s.Select( x => new SelectListItem { Text = x.Name, Value = x.Id.ToString(), Selected = ViewData.Model.Class1.Class2s.Any(y => y.Id == x.Id) }) They have many to many mapping. I have a ListBox in Class1 view which displays Class2. How to map the output of the ListBox back to IList Class2s property of Class1? I am able to display the values in the ListBox but unable to map back the SelectListItem to IList.

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