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• LINQ query on a DataTable

  - by Calanus

  I'm trying to perform a LINQ query on a DataTable object and bizarrely I am finding that performing such queries on DataTables is not straightforward. For example: var results = from myRow in myDataTable where results.Field("RowNo") == 1 select results; This is not allowed. Any ideas how to get something like this working? I'm amazed that LINQ queries are not allowed on DataTables!

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• Can you reverse order a string in one line with LINQ or a LAMBDA expression

  - by Student for Life

  Not that I would want to use this practically (for many reasons) but out of strict curiousity I would like to know if there is a way to reverse order a string using LINQ and/or LAMBDA expressions in one line of code, without utilising any framework "Reverse" methods. e.g. string value = "reverse me"; string reversedValue = (....); and reversedValue will result in "em esrever" EDIT Clearly an impractical problem/solution I know this, so don't worry it's strictly a curiosity question around the LINQ/LAMBDA construct.

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• LINQ Query vs Lambda Expression

  - by FosterZ

  What is the difference between the following two snippets (i.e LINQ Query vs Lambda Expression) LINQ Query public Product GetProduct(int productID) { AdventureWorksDBDataContext db = new AdventureWorksDBDataContext(); Product product = (from p in db.Products where p.ProductID == productID select p).Single(); return product; } Using a Lambda expression public Product GetProduct(int productID) { AdventureWorksDBDataContext db = new AdventureWorksDBDataContext(); Product product = db.Products.Single(p = p.ProductID == productID); return product; }

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• Turn Function or Stored Procedure Result into "live" Result for LINQ

  - by Alex

  Is it possible to turn result sets obtained in LINQ through a stored procedure or function call into a "live" set of objects of which I can retrieve Foreign Key related objects? If, for example, my stored procedure returns a set of rows (= LINQ objects) of type "Contact", then I can't seem to obtain Contact.BillingAddress (which is related by Foreign Key). Any idea how to make this work?

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• Linq to SQL - Error handling

  - by Sundararajan S

  I have a linq to sql statement that inserts records in the database. If there is a duplicate, it throws Primary key violation . after this happens, whenever i try to execute any other statement, it repeatedly shows this error. Is this a problem of transaction not getting closed. Also how to handle transactions in a more reliable way in LINQ to SQL

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• How convert sql query to linq-to-sql

  - by name1ess0ne

  I have Sql query: SELECT News.NewsId, News.Subject, Cm.Cnt FROM dbo.News LEFT JOIN (SELECT Comments.OwnerId, COUNT(Comments.OwnerId) as Cnt FROM Comments WHERE Comments.CommentType = 'News' Group By Comments.OwnerId) Cm ON Cm.OwnerId = News.NewsId But I want linq-to-sql query, how I can convert this to linq?

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• Linq-to-SQL: how many datacontexts ?

  - by sh00

  I have a SQL Server 2008 database with 300 tables. The application I have to design is an Windows Forms app, .NET 3.5, C#. Which is the best way to work with Linq-to-SQL ? I intend to make a datacontext for each business entity. Is there any problem ? I need to know if this way of working with Linq-to-SQL has any disadvantage or can create performance issues ? Thanks.

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• Counting words in a collection using LINQ

  - by icemanind

  Guys, I have a StringCollection object with 5 words in them. 3 of them are duplicate words. I am trying to create a LINQ query that will count how many unique words are in the collection and output them to to the console. So, for example, if my StringCollection has 'House', 'Car,'House','Dog', 'Cat', then it should output like this: House -- 2 Car -- 1 Dog -- 1 Cat -- 1 any ideas on how to create a LINQ query to do this?

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• how to delete all records from database using linq

  - by Samir

  how to delete all records from database using linq.i want to delete all records from the database using linq.i am using MVC.so please tell me the code to delete all records using repository. reply me soon thanks samir

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• Implement LINQ to Entities unsupported method

  - by Dan

  Hi! LINQ to Entities has many LINQ methods marked as "Unsupported" (http://msdn.microsoft.com/en-us/library/bb738550.aspx). Is any way to implement some of these methods by hands? Or I should wait next release of EF? I'm especially needing this method: IQueryable<TResult> Select<TSource, TResult>(this IQueryable<TSource> source, Expression<Func<TSource, int, TResult>> selector) Thanks

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• Coolest C# LINQ/Lambdas trick you've ever pulled?

  - by chakrit

  Saw a post about hidden features in C# but not a lot of people have written linq/lambdas example so... I wonder... What's the coolest (as in the most elegant) use of the C# LINQ and/or Lambdas/anonymous delegates you have ever saw/written? Bonus if it has went into production too!

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• Retrieving top 50 rows from Table using LINQ

  - by James

  Hey, Am new to LINQ, and am trying to retrieve the top 50 rows of a particular table. In SQL Server using an actual query i coudl say "Select TOP 50 from Transactions" , but not sure how i need to do that with LinQ Any pointers that could help ? Thanks !

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• how to convert sql union to linq

  - by lowlyintern

  I have the following Transact SQL query using a union. I need some pointers as to how this would look in LINQ i.e some examples wouldbe nice or if anyone can recommend a good tutorial on UNIONS in linq. select top 10 Barcode, sum(ItemDiscountUnion.AmountTaken) from (SELECT d.Barcode,SUM(AmountTaken) AmountTaken FROM [Aggregation].[dbo].[DiscountPromotion] d GROUP BY d.Barcode UNION ALL SELECT i.Barcode,SUM(AmountTaken) AmountTaken FROM [Aggregation].[dbo].ItemSaleTransaction i group by i.Barcode) ItemDiscountUnion group by Barcode

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• ASP.NET MVC 2: Linq to SQL entity w/ ForeignKey relationship and Default ModelBinder strangeness

  - by Simon

  Once again I'm having trouble with Linq to Sql and the MVC Model Binder. I have Linq to Sql generated classes, to illustrate them they look similar to this: public class Client { public int ClientID { get; set; } public string Name { get; set; } } public class Site { public int SiteID { get; set; } public string Name { get; set; } } public class User { public int UserID { get; set; } public string Name { get; set; } public int? ClientID { get; set; } public EntityRef<Client> Client { get; set; } public int? SiteID { get; set; } public EntityRef<Site> Site { get; set; } } The 'User' has a relationship with the 'Client' and 'Site . The User class has nullable ClientIDs and SiteIDs because the admin users are not bound to a Client or Site. Now I have a view where a user can edit a 'User' object, the view has fields for all the 'User' properties. When the form is submitted, the appropiate 'Save' action is called in my UserController: public ActionResult Save(User user, FormCollection form) { //form['SiteID'] == 1 //user.SiteID == 1 //form['ClientID'] == 1 //user.ClientID == null } The problem here is that the ClientID is never set, it is always null, even though the value is in the FormCollection. To figure out whats going wrong I set breakpoints for the ClientID and SiteID getters and setters in the Linq to Sql designer generated classes. I noticed the following: SiteID is being set, then ClientID is being set, but then the Client EntityRef property is being set with a null value which in turn is setting the ClientID to null too! I don't know why and what is trying to set the Client property, because the Site property setter is never beeing called, only the Client setter is being called. Manually setting the ClientID from the FormCollection like this: user.ClientID = int.Parse(form["ClientID"].ToString()); throws a 'ForeignKeyReferenceAlreadyHasValueException', because it was already set to null before. The only workaround I have found is to extend the generated partial User class with a custom method: Client = default(EntityRef<Client>) but this is not a satisfying solution. I don't think it should work like this? Please enlighten me someone. So far Linq to Sql is driving me crazy! Best regards

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• Group By Multiple Columns - LINQ

  - by Nev_Rahd

  How can I do GroupBy Multiple Columns in LINQ Something as in SQL : SELECT * FROM <TableName> GROUP BY <Column1>,<Column2> How Can i convert below to LINQ QuantityBreakdown ( MaterialID int, ProductID int, Quantity float ) INSERT INTO @QuantityBreakdown (MaterialID, ProductID, Quantity) SELECT MaterialID, ProductID, SUM(Quantity) FROM @Transactions GROUP BY MaterialID, ProductID Thanks

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• linq to entites left outer join

  - by parminder

  I am struggling linq to entities left outer join. I have two entities (tables): Listings { ListingID, MakeID (nullable) } Makes { MakeID, Description } I want to write something like this in LINQ: select listings.listingID ,listings.makeid , IsNull(makes.Description, 'NA') from listings left outer join makes on listings.makeid = makes.makeid

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• asp.net mvc linq sql problem

  - by user339449

  Hi all, Now I am working on project using asp.net mvc 2 and linq to sql, the problem is occurs when trying to insert data in a table where the table has an identity column type of tinyint. When trying to insert the error following error occurs, The primary key column of type 'TinyInt' cannot be generated by the server. What is the problem, does linq to sql support tinyint datatype? Please help me

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• return a single list property List in Linq

  - by bharat

  I am having an issue here i have a list this.Ddown having 3 properties i want to write a Linq Query to return one of the property lets say i have property a,b,c i want to retutn list(c) how do i do that in linq

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• Where is System.Linq in .NET 4.0?

  - by Tony_Henrich

  I migrated an asp.net app to 4.0. Now I am getting an error "The type or namespace name 'IQueryable' could not be found". The reference to System.Linq is invalid and I can't find it in the reference list. Where did System.Linq go?

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• Query a List of List of Items in LINQ c#

  - by call me Steve

  I am a bit new to LINQ, here is my problem. I have a List of List of Items I like to get the Items which are present in only one List (and if I could get the List in which they are without re-iterating through the "list of list" that would be great). I am trying without success to use the Aggregate / Except / Group keywords in the Linq query but nothing close to a solution so far.

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• LINQ expression until to break a string

  - by wonea

  Using LINQ I'm looking to break down the following path string[], however I'd like to break it up to the point of the Binn folder. Is there a WHERE UNTIL operator in LINQ? c:\ Program Files\ Microsoft SQL Server\ MSSQL10.SQLEXPRESS\ MSSQL\ Binn\ sqlservr.exe What I'd like todo var words = from word in thepath where UNTIL thepath == "Binn" select word;

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• How to get datarow array refering to datatable 's field value with linq

  - by Michael

  I want to use linq to get datarow array from a datatable which its string type ColumnA is not null or depending on its length 0 , so I can get the row index with Indexof() method to deal with something else. ColumnA ColumnB ColumnC A0 B0 C0 Null B1 C1 A2 B2 C2 Null B3 C3 My Linq Statment: DataRow[] rows = myDataTable.Select("ColumnA is not null").Where(row=>row.Field<string>("ColumnA").Length>0); somebody who can help?

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• Castle ActiveRecord using Linq to Nhibernate Example

  - by Eric Neunaber

  I have been using the ActiveRecord library for many years. Recently I started a new project and I'm including the AR 2.0 release in this project. I saw that it shipped with the Linq to Nhibernate library. Are there any good examples of how to use Linq to Nhibernate with the Active Record library?

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• Translate Linq Expression to any existing Query structure?

  - by fredlegrain

  I have some kind of "data engine" between multiple "data consumer" processes and multiple "data storage" sources. I'd like to provide Linq capabilities to the "data consumer" and forward the query to the "data storage". The forwarded query should be some structured query (like, let's say, NHibernate Criteria). Is there any existing structured query library that could allow me to "just" translate a Linq Expression to such a structured query?

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• how to bind gridview through linq

  - by Manoj Wadhwani

  I am using linq to sql Currently i am binding gridviw through linq which query written in business logic call . i have extract record through query in business logic class and i want to bind that particular data to gridviw and return data . how to retrun data which type is array. code is mention below: CMSBusiness.DataClasses1DataContext db = new DataClasses1DataContext(); var cate = from p in db.categoryTables select new { categoryId=p.categoryId, categoryName=p.categoryName, categoryDesc=p.categoryDesc }; how to return value and bind gridview , Please suggest

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