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• Exception handling in Linq to SQL for customers without orders

  - by stackoverflowuser

  I have the following code to retrieve customer name, total (orders ), sum (order details) for reach customer in Northwind database. The problem with below code is that it raises an exception since a few customers dont have any entry in orders table. I know using the query syntax (join) the exception can be avoided. I want to know if the same can be handled with the extension method syntax. var customerOrders = db.Customers .Select(c => new { CompanyName = c.CompanyName, TotalOrders = c.Orders.Count(), TotalQuantity = c.Orders .SelectMany(o => o.Order_Details).Sum(o=>o.Quantity) });

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• Linq qurery with multiple where's

  - by Dan

  I am trying the to query my Status Update repository using the following var result = (from s in _dataContext.StatusUpdates where s.Username == "friend1" && s.Username == "friend2" etc... select s).ToList(); Insead of using s.Username == "friendN" continously is there anyway I can pass a list or array or something like that rather that specifying each one, or can i use a foreach loop in the middle of the query. Thanks

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• XDocument + IEnumerable is causing out of memory exception in System.Xml.Linq.dll

  - by Manatherin

  Basically I have a program which, when it starts loads a list of files (as FileInfo) and for each file in the list it loads a XML document (as XDocument). The program then reads data out of it into a container class (storing as IEnumerables), at which point the XDocument goes out of scope. The program then exports the data from the container class to a database. After the export the container class goes out of scope, however, the garbage collector isn't clearing up the container class which, because its storing as IEnumerable, seems to lead to the XDocument staying in memory (Not sure if this is the reason but the task manager is showing the memory from the XDocument isn't being freed). As the program is looping through multiple files eventually the program is throwing a out of memory exception. To mitigate this ive ended up using System.GC.Collect(); to force the garbage collector to run after the container goes out of scope. this is working but my questions are: Is this the right thing to do? (Forcing the garbage collector to run seems a bit odd) Is there a better way to make sure the XDocument memory is being disposed? Could there be a different reason, other than the IEnumerable, that the document memory isnt being freed? Thanks. Edit: Code Samples: Container Class: public IEnumerable<CustomClassOne> CustomClassOne { get; set; } public IEnumerable<CustomClassTwo> CustomClassTwo { get; set; } public IEnumerable<CustomClassThree> CustomClassThree { get; set; } ... public IEnumerable<CustomClassNine> CustomClassNine { get; set; }</code></pre> Custom Class: public long VariableOne { get; set; } public int VariableTwo { get; set; } public DateTime VariableThree { get; set; } ... Anyway that's the basic structures really. The Custom Classes are populated through the container class from the XML document. The filled structures themselves use very little memory. A container class is filled from one XML document, goes out of scope, the next document is then loaded e.g. public static void ExportAll(IEnumerable<FileInfo> files) { foreach (FileInfo file in files) { ExportFile(file); //Temporary to clear memory System.GC.Collect(); } } private static void ExportFile(FileInfo file) { ContainerClass containerClass = Reader.ReadXMLDocument(file); ExportContainerClass(containerClass); //Export simply dumps the data from the container class into a database //Container Class (and any passed container classes) goes out of scope at end of export } public static ContainerClass ReadXMLDocument(FileInfo fileToRead) { XDocument document = GetXDocument(fileToRead); var containerClass = new ContainerClass(); //ForEach customClass in containerClass //Read all data for customClass from XDocument return containerClass; } Forgot to mention this bit (not sure if its relevent), the files can be compressed as .gz so I have the GetXDocument() method to load it private static XDocument GetXDocument(FileInfo fileToRead) { XDocument document; using (FileStream fileStream = new FileStream(fileToRead.FullName, FileMode.Open, FileAccess.Read, FileShare.Read)) { if (String.Compare(fileToRead.Extension, ".gz", true) == 0) { using (GZipStream zipStream = new GZipStream(fileStream, CompressionMode.Decompress)) { document = XDocument.Load(zipStream); } } else { document = XDocument.Load(fileStream); } return document; } } Hope this is enough information. Thanks Edit: The System.GC.Collect() is not working 100% of the time, sometimes the program seems to retain the XDocument, anyone have any idea why this might be?

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• Copy Rows in a One to Many with LINQ (2 SQL)

  - by Refracted Paladin

  I have a table that stores a bunch of diagnosis for a single plan. When the users create a new plan I need to copy over all existing diagnosis's as well. I had thought to try the below but this is obviously not correct. I am guessing that I will need to loop through my oldDiagnosis part, but how? Thanks! My Attempt so far... public static void CopyPlanDiagnosis(int newPlanID, int oldPlanID) { using (var context = McpDataContext.Create()) { var oldDiagnosis = from planDiagnosi in context.tblPlanDiagnosis where planDiagnosi.PlanID == oldPlanID select planDiagnosi; var newDiagnosis = new tblPlanDiagnosi { PlanID = newPlanID, DiagnosisCueID = oldDiagnosis.DiagnosisCueID, DiagnosisOther = oldDiagnosis.DiagnosisOther, AdditionalInfo = oldDiagnosis.AdditionalInfo, rowguid = Guid.NewGuid() }; context.tblPlanDiagnosis.InsertOnSubmit(newDiagnosis); context.SubmitChanges(); } }

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• How to retrieve indentity column vaule after insert using LINQ

  - by Hobey

  Could any of you please show me how to complete the following tasks? // Prepare object to be saved // Note that MasterTable has MasterTableId as a Primary Key and it is an indentity column MasterTable masterTable = new MasterTable(); masterTable.Column1 = "Column 1 Value"; masterTable.Column2 = 111; // Instantiate DataContext DataContext myDataContext = new DataContext("<<ConnectionStrin>>"); // Save the record myDataContext.MasterTables.InsertOnSubmit(masterTable); myDataContext.SubmitChanges(); // ?QUESTION? // Now I need to retrieve the value of MasterTableId for the record just inserted above. Kind Regards

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• LINQ to XML: suppressing redundant namespace attribute in child nodes

  - by GSerg

  If a node belongs to a namespace, it's children by default belong to the same namespace. So there's no need to provide an xmlns attribute on each child, which is good. However. If I create two nodes like this: Dim parent = <parent xmlns="http://my.namespace.org"/> Dim child = <child xmlns="http://my.namespace.org">value</child> parent.Add(child) Console.WriteLine(parent.ToString) The result is this: <parent xmlns="http://my.namespace.org"> <child xmlns="http://my.namespace.org">value</child> </parent> But, if create them in a less convenient way: Dim parent = <parent xmlns="http://my.namespace.org"/> Dim child As New XElement(XName.Get("child", "http://my.namespace.org")) With {.Value = "value"} parent.Add(child) Console.WriteLine(parent.ToString) The result is more desirable: <parent xmlns="http://my.namespace.org"> <child>value</child> </parent> Obviously, I'd prefer to use the first way because it is so much more intuitive and easy to code. There's also another reason to not use method 2 -- sometimes I need to create nodes with XElement.Parse, parsing a string that contains an xmlns attribute, which produces exactly same results as method 1. So the question is -- how do I get the pretty output of method 2, creating nodes as in method 1? The only option I see is to create a method that would clone given XElement, effectively recreating it according to method 2 pattern, but that seems ugly. I'm looking for a more obvious solution I overlooked for some reason.

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• Copy Rows in a One to Many with LINQ to SQL

  - by Refracted Paladin

  I have a table that stores a bunch of diagnosis for a single plan. When the users create a new plan I need to copy over all existing diagnosis's as well. I had thought to try the below but this is obviously not correct. I am guessing that I will need to loop through my oldDiagnosis part, but how? Thanks! My Attempt so far... public static void CopyPlanDiagnosis(int newPlanID, int oldPlanID) { using (var context = McpDataContext.Create()) { var oldDiagnosis = from planDiagnosi in context.tblPlanDiagnosis where planDiagnosi.PlanID == oldPlanID select planDiagnosi; var newDiagnosis = new tblPlanDiagnosi { PlanID = newPlanID, DiagnosisCueID = oldDiagnosis.DiagnosisCueID, DiagnosisOther = oldDiagnosis.DiagnosisOther, AdditionalInfo = oldDiagnosis.AdditionalInfo, rowguid = Guid.NewGuid() }; context.tblPlanDiagnosis.InsertOnSubmit(newDiagnosis); context.SubmitChanges(); } }

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• LINQ and the use of Repeat and Range operator

  - by vik20000in

  LINQ is also very useful when it comes to generation of range or repetition of data.  We can generate a range of data with the help of the range method.     var numbers =         from n in Enumerable.Range(100, 50)         select new {Number = n, OddEven = n % 2 == 1 ? "odd" : "even"}; The above query will generate 50 records where the record will start from 100 till 149. The query also determines if the number is odd or even. But if we want to generate the same number for multiple times then we can use the Repeat method.     var numbers = Enumerable.Repeat(7, 10); The above query will produce a list with 10 items having the value 7. Vikram

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• Sort method versus OrderBy LINQ extension method

  - by nmarun

  I have a class Product with an Id and a Name as properties. There are multiple ways of getting a list of products to display in sorted/ordered fashion, say, by the Name of the product. The two I’m concerned about here are the Sort and the OrderBy extension method through LINQ and the difference between them. 1: public class Product 2: { 3: public int Id { get; set; } 4: public string Name { get; set; } 5: } Below is the list of products that I’ll be using and is defined somewhere in the Program.cs...(read more)

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• LINQ/LAMBDA filter query by date [on hold]

  - by inquisitive_one

  I'm trying to use LINQ to SQL to retrieve earnings data for a particular date range. Currently the table is set up as follows: Comp Eps Year Quarter IBM .5 2012 2 IBM .65 2012 3 IBM .60 2012 4 IBM .5 2011 2 IBM .7 2013 1 IBM .8 2013 2 Except for Eps, all fields have a data type of string or char. Eps has a data type of double. Here's my code: var myData = myTable .Where(t => t.Comp.Equals("IBM") && Convert.Int32(string.Format("{0}{1}", t.Year, t.Quarter)) <= 20131); I get the following error when I tried that code: Method 'System.String Format(System.String, System.Object, System.Object)' has no supported translation to SQL How can I select all Eps that has a year & quarter less than "20132" using a lambda expression?

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• Using linq to parse file [closed]

  - by Emaan Abdul majeed

  i am working parsing textfile using LINQ but got struc on it,its going outof range exception string[] lines = File.ReadAllLines(input); var t1 = lines .Where(l => !l.StartsWith("#")) .Select(l => l.Split(' ')) .Select(items => String.Format("{0}{1}{2}", items[1].PadRight(32), //items[1].PadRight(16) items[2].PadRight(32), items[3].PadRight(32))); var t2 = t1 .Select(l => l.ToUpper()); foreach (var t in t2) Console.WriteLine(t); and file is about 200 to 500 lines and i want to extract specific information so i need to split that information to different structure so how to do it this..

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• Is there something like LINQ for Java?

  - by Kb

  Started to learn LINQ with C#. Especially LINQ to Objects and LINQ to XML. I really enjoy the power of LINQ. I learned that there is something called JLINQ a Jscript implementation. Also (as Catbert posted) Scala will have LINQ Do you know if LINQ or something similar will be a part of Java 7? Update: Interesting post from 2008 - http://stackoverflow.com/questions/346721/linq-for-java

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• With NHibernate, how can I add a child object when updating a parent object?

  - by BMZ

  I have a simple Parent/Child relationship between a Person object and an Address object. The Person object exists in the DB. After doing a Get on the Person, I add a new Address object to the Address sub-object list of the parent, and do some other updates to the Person object. Finally, I do an Update on the Person object. With a SQL trace window, I can see the update to the Person object to the Person table and the Insert of the Address record to the Address table. The issue is that, after the update is performed, the AddressId (primary key on the Address object) is still set to 0, which is what it defaults to when you first initialize the Address object. I have verified that when I do an Add, this value is set correctly. Is this a known issue when trying to add sub-objects as part of an NHibernate UPDATE? Sample code and mapping files are below Thanks <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"> <class name="BusinessEntities.Wellness.Person,BusinessEntities.Wellness" table="Person" lazy="true" dynamic-insert="true" dynamic-update="false"> <id name="Personid" column="PersonID" type="int"> <generator class="native" /> </id> <version type="binary" generated="always" name="RecordVersion" column="`RecordVersion`"/> <property type="int" not-null="true" name="Customerid" column="`CustomerID`" /> <property type="AnsiString" not-null="true" length="9" name="Ssn" column="`SSN`" /> <property type="AnsiString" not-null="true" length="30" name="FirstName" column="`FirstName`" /> <property type="AnsiString" not-null="true" length="35" name="LastName" column="`LastName`" /> <property type="AnsiString" length="1" name="MiddleInitial" column="`MiddleInitial`" /> <property type="DateTime" name="DateOfBirth" column="`DateOfBirth`" /> <bag name="PersonAddresses" inverse="true" lazy="true" cascade="all"> <key column="PersonID" /> <one-to-many class="BusinessEntities.Wellness.PersonAddress,BusinessEntities.Wellness" / </bag> </class> </hibernate-mapping> <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"> <class name="BusinessEntities.Wellness.PersonAddress,BusinessEntities.Wellness" table="PersonAddress" lazy="true" dynamic-insert="true" dynamic-update="false"> <id name="PersonAddressId" column="PersonAddressID" type="int"> <generator class="native" /> </id> <version type="binary" generated="always" name="RecordVersion" column="`RecordVersion`" /> <property type="AnsiString" not-null="true" length="1" name="AddressTypeid" column="`AddressTypeID`" /> <property type="AnsiString" not-null="true" length="60" name="AddressLine1" column="`AddressLine1`" /> <property type="AnsiString" length="60" name="AddressLine2" column="`AddressLine2`" /> <property type="AnsiString" length="60" name="City" column="`City`" /> <property type="AnsiString" length="2" name="UsStateId" column="`USStateID`" /> <property type="AnsiString" length="5" name="UsPostalCodeId" column="`USPostalCodeID`" /> <many-to-one name="Person" cascade="none" column="PersonID" /> </class> </hibernate-mapping> Person newPerson = new Person(); newPerson.PersonName = "John Doe"; newPerson.SSN = "111111111"; newPerson.CreatedBy = "RJC"; newPerson.CreatedDate = DateTime.Today; personDao.AddPerson(newPerson); Person updatePerson = personDao.GetPerson(newPerson.PersonId); updatePerson.PersonAddresses = new List<PersonAddress>(); PersonAddress addr = new PersonAddress(); addr.AddressLine1 = "1 Main St"; addr.City = "Boston"; addr.State = "MA"; addr.Zip = "12345"; updatePerson.PersonAddresses.Add(addr); personDao.UpdatePerson(updatePerson); int addressID = updatePerson.PersonAddresses[0].AddressId;

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• Maintain denormalized data with NHibernate EventListener

  - by Michael Valenty

  I have one bit of denormalized data used for performance reasons and I'm trying to maintain the data with an NHibernate event listener rather than a trigger. I'm not convinced this is the best approach, but I'm neck deep into it and I want to figure this out before moving on. I'm getting following error: System.InvalidOperationException : Collection was modified; enumeration operation may not execute. System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource) System.Collections.Generic.List`1.Enumerator.MoveNextRare() System.Collections.Generic.List`1.Enumerator.MoveNext() NHibernate.Engine.ActionQueue.ExecuteActions(IList list) NHibernate.Engine.ActionQueue.ExecuteActions() NHibernate.Event.Default.AbstractFlushingEventListener.PerformExecutions (IEventSource session) NHibernate.Event.Default.DefaultFlushEventListener.OnFlush(FlushEvent event) NHibernate.Impl.SessionImpl.Flush() NHibernate.Transaction.AdoTransaction.Commit() Here's the code to make happen: using (var tx = session.BeginTransaction()) { var business = session .Get<Business>(1234) .ChangeZipCodeTo("92011"); session.Update(business); tx.Commit(); // error happens here } and the event listener: public void OnPostUpdate(PostUpdateEvent @event) { var business = @event.Entity as Business; if (business != null) { var links = @event.Session .CreateQuery("select l from BusinessCategoryLink as l where l.Business.BusinessId = :businessId") .SetParameter("businessId", business.BusinessId) .List<BusinessCategoryLink>(); foreach (var link in links) { link.Location = business.Location; @event.Session.Update(link); } } }

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• ASP.NET MVC and NHibernate coupling

  - by Ben

  I have just started learning NHibernate. Over the past few months I have been using IoC / DI (structuremap) and the repository pattern and it has made my applications much more loosely coupled and easier to test. When switching my persistence layer to NHibernate I decided to stick with my repositories. Currently I am creating a new session on each method call but of course this means that I can not benefit from lazy loading. Therefore I wish to implement session-per-request but in doing so this will make my web project dependent on NHibernate (perhaps this is not such a bad thing?). I was planning to inject ISession into my repositories and create and dispose sessions on beginrequest/endrequest events (see http://ayende.com/Blog/archive/2009/08/05/do-you-need-a-framework.aspx) Is this a good approach? Presumably I cannot use session-per-request without having a reference to NHibernate in my web project? Having the web project dependent on NHibernate prompts my next (few) questions - why even bother with the repository? Since my web app is calling services that talk to the repositories, why not ditch the repositories and just add my NHibernate persistance code inside the services? And finally, is there really any need to split out into so many projects. Is a web project and an infrastructure project sufficient? I realise that I have veered off a bit from my original question but it seems that everyone seems to have their own opinion on these topics. Some people use the repository pattern with NHibernate, some don't. Some people stick their mapping files with the related classes, others have a separate project for this. Many thanks, Ben

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• Is it possible to unit test methods that rely on NHibernate Detached Criteria?

  - by Aim Kai

  I have tried to use Moq to unit test a method on a repository that uses the DetachedCriteria class. But I come up against a problem whereby I cannot actually mock the internal Criteria object that is built inside. Is there any way to mock detached criteria? Test Method [Test] [Category("UnitTest")] public void FindByNameSuccessTest() { //Mock hibernate here var sessionMock = new Mock<ISession>(); var sessionManager = new Mock<ISessionManager>(); var queryMock = new Mock<IQuery>(); var criteria = new Mock<ICriteria>(); var sessionIMock = new Mock<NHibernate.Engine.ISessionImplementor>(); var expectedRestriction = new Restriction {Id = 1, Name="Test"}; //Set up expected returns sessionManager.Setup(m => m.OpenSession()).Returns(sessionMock.Object); sessionMock.Setup(x => x.GetSessionImplementation()).Returns(sessionIMock.Object); queryMock.Setup(x => x.UniqueResult<SopRestriction>()).Returns(expectedRestriction); criteria.Setup(x => x.UniqueResult()).Returns(expectedRestriction); //Build repository var rep = new TestRepository(sessionManager.Object); //Call repostitory here to get list var returnR = rep.FindByName("Test"); Assert.That(returnR.Id == expectedRestriction.Id); } Repository Class public class TestRepository { protected readonly ISessionManager SessionManager; public virtual ISession Session { get { return SessionManager.OpenSession(); } } public TestRepository(ISessionManager sessionManager) { } public SopRestriction FindByName(string name) { var criteria = DetachedCriteria.For<Restriction>().Add<Restriction>(x => x.Name == name) return criteria.GetExecutableCriteria(Session).UniqueResult<T>(); } } Note I am using "NHibernate.LambdaExtensions" and "Castle.Facilities.NHibernateIntegration" here as well. Any help would be gratefully appreciated.

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• Change nhibernate config with nant xmlpoke

  - by isuruceanu

  Hi All How can I change the connection string from nhibernate.config file using nant the problem is that all examples are about changing attribute value, but nhibernate has inner text eq: <hibernate-configuration xmlns="urn:nhibernate-configuration-2.2"> <session-factory> <property name="connection.connection_string">Data Source.\server;Database=UnitTestDb;UID=user;pwd=pass;</property> <property name="dialect">NHibernate.Dialect.MsSql2008Dialect</property> <property name="connection.provider">NHibernate.Connection.DriverConnectionProvider</property> <property name="connection.driver_class">NHibernate.Driver.SqlClientDriver</property> <property name="show_sql">true</property> <property name="connection.release_mode">auto</property> <property name="adonet.batch_size">500</property> .... I need to change property connection.connection_string <xmlpoke file="${nhibernate.file}" xpath="/hibernate-configuration/session-factory/add[@key='connection.connection_string']/@value" value="${connection.string}"> </xmlpoke> this does not work in this case. Thanks

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• NHibernate is not connecting to sql server.

  - by user177883

  When i set up a regular connection, it works, however when i try to use nhibernate, hibernate.cfg.xml, i m getting the following error. Message="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)" Source=".Net SqlClient Data Provider" What would be the reason for this and how can i resolve it ? I doubt that it s a network or sql server configuration error. <?xml version="1.0" ?> <hibernate-configuration xmlns="urn:nhibernate-configuration-2.2" > <session-factory> <property name="connection.provider">NHibernate.Connection.DriverConnectionProvider</property> <property name="dialect">NHibernate.Dialect.MsSql2005Dialect</property> <property name="connection.driver_class">NHibernate.Driver.SqlClientDriver</property> <property name="connection.connection_string">Server=(ServerName\DEV_ENV);Initial Catalog=dbName;User Id=SA;Password=PASS</property> <property name="proxyfactory.factory_class">NHibernate.ByteCode.LinFu.ProxyFactoryFactory, NHibernate.ByteCode.LinFu</property> </session-factory> </hibernate-configuration>

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• NHibernate - Retrieving Lots of Data Becomes Exponentially Slow

  - by nfplee

  Hi, I have an issue when I retrieve lots of data in NHibernate (such as when producing a report) the page becomes exponentially slower the more data it has to retrieve. I found the following article: http://nhforge.org/blogs/nhibernate/archive/2008/10/30/bulk-data-operations-with-nhibernate-s-stateless-sessions.aspx It explains how doing bulk data operations in NHibernate is slow since the first level cache grows too large and how you should use the IStatelessSession instead. The trouble I have is that I don't wish to tie my application to NHibernate so I've added a wrapper around ISession. I then use Linq as my query mechanism but IStatelessSession does not support Linq (it may do in NHibernate 3 but the Linq provider is not stable as it stands at the moment). I then read that you could do a clear after so many iterations to clear out the first level cache. The problem now is that you can't use lazy loading. The linq provider doesn't allow you to override the mapping defined (or eagerly fetch the additional data) so whenever I grab data which is lazy loaded after I have cleared the session an exception is thrown. I'm completely lost on what do now. I like the ease of producing reports with linq but the limitations of the inbuilt linq provider in NHibernate seem to be holding me back. I'd really appreciate it if someone could show me an alternative approach. Thanks

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• LINQ 2 Entities , howto check DateTime.HasValue within the linq query

  - by Snoop Dogg

  Hi all ... I have this method that is supposed to get the latest messages posted, from the Table (& EntitySet) called ENTRY ///method gets "days" as parameter, used in new TimeSpan(days,0,0,0);!! using (Entities db = new Entities()) { var entries = from ent in db.ENTRY where ent.DATECREATE.Value > DateTime.Today.Subtract(new TimeSpan(days, 0, 0, 0)) select new ForumEntryGridView() { id = ent.id, baslik = ent.header, tarih = ent.entrydate.Value, membername = ent.Member.ToString() }; return entries.ToList<ForumEntryGridView>(); } Here the DATECREATED is Nullable in the database. I cant place "if"s in this query ... any way to check for that? Thx in advance

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• Simple linq question: using linq to get an array of properties

  - by Joel Barsotti

  Lets say we have a simple class public class Foo { public string FooName; } Now we want to do some simple work on it. public void SomeCallerMethod(List<Foo> listOfFoos) { string[] fooNames = listOfFoo. // What to do here? } If I even knew what method to call, I could probably find the rest of the peices.

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• LINQ: Single vs. First

  - by Paulo Morgado

  I’ve witnessed and been involved in several discussions around the correctness or usefulness of the Single method in the LINQ API. The most common argument is that you are querying for the first element on the result set and an exception will be thrown if there’s more than one element. The First method should be used instead, because it doesn’t throw if the result set has more than one item. Although the documentation for Single states that it returns a single, specific element of a sequence of values, it actually returns THE single, specific element of a sequence of ONE value. One you use the Single method in your code you are asserting that your query will result in a scalar result instead of a result set of arbitrary length. On the other hand, the documentation for First states that it returns the first element of a sequence of arbitrary length. Imagine you want to catch a taxi. You go the the taxi line and catch the FIRST one, no matter how many are there. On the other hand, if you go the the parking lot to get your car, you want the SINGLE one specific car that’s yours. If your “query” “returns” more than one car, it’s an exception. Either because it “returned” not only your car or you happen to have more than one car in that parking lot. In either case, you can only drive one car at once and you’ll need to refine your “query”.

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• TakeWhile and SkipWhile method in LINQ

  - by vik20000in

   In my last post I talked about how to use the take and the Skip keyword to filter out the number of records that we are fetching. But there is only problem with the take and skip statement. The problem lies in the dependency where by the number of records to be fetched has to be passed to it. Many a times the number of records to be fetched is also based on the query itself. For example if we want to continue fetching records till a certain condition is met on the record set. Let’s say we want to fetch records from the array of number till we get 7. For this kind of query LINQ has exposed the TakeWhile Method.     int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };     var firstNumbersLessThan6 = numbers.TakeWhile(n => n < 7);   In the same way we can also use the SkipWhile statement. The skip while statement will skip all the records that do not match certain condition provided. In the example below we are skiping all those number which are not divisible by 3. Remember we could have done this with where clause also, but SkipWhile method can be useful in many other situation and hence the example and the keyword.     int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };     var allButFirst3Numbers = numbers.SkipWhile(n => n % 3 != 0); Vikram

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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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• problem with NHibernate and iSeries DB2

  - by chrisjlong

  Ok So I have an AS400/iSeries running v5r4. I have an application that was using classic NHibernate to connect and do some basic crud. Now I have pulled that app (which sat for 2 years) off the shelf of TFS and onto a new PC and cannot seem to get it running. Here is my Hibernate Config: <hibernate-configuration xmlns="urn:nhibernate-configuration-2.2"> <session-factory> <property name="connection.provider"> NHibernate.Connection.DriverConnectionProvider </property> <property name="dialect"> NHibernate.Dialect.DB2400Dialect </property> <property name="proxyfactory.factory_class">NHibernate.ByteCode.LinFu.ProxyFactoryFactory, NHibernate.ByteCode.LinFu</property> <property name="connection.connection_string"> DataSource=207.206.106.19; Database=AS400; userID=XXXXXX; Password=XXXXXXX; LibraryList=FMSFILTST,BEFFILT,HRDBFT,HRCSTFT,J20##X2DEV,GLCUSTDEV,OSL@@F3DEV; Naming=System; Initial Catalog=*SYSBAS; </property> <property name="use_outer_join">true</property> <property name="query.substitutions"> true 1, false 0, yes 'Y', no 'N' </property> <property name="show_sql">false</property> <mapping assembly="BusinessLogic" /> </session-factory> </hibernate-configuration> I have all the proper DLL's included (NHibernate, castle, iesi, antlr3 , log4 etc). Also have this line in my web.config <runtime> <assemblyBinding> <qualifyAssembly partialName="IBM.Data.DB2.iSeries" fullName="IBM.Data.DB2.iSeries,Version=10.0.0.0,PublicKeyToken=9CDB2EBFB1F93A26,Culture=neutral"/> </assemblyBinding> </runtime> Yet I am still getting the following error as soon as I call NHibernate.Cfg.Configuration().Configure().BuildSessionFactory().OpenSession(); The error is as follows Unable to cast object of type 'IBM.Data.DB2.iSeries.iDB2Connection' to type 'System.Data.Common.DbCommand' I am dying to get some help with this. Any assistance is appreciated. Thanks!

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