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  • "Select NOT IN" clause in Linq to Entities

    - by lnetanel
    Hi, Is there a way to use the "NOT IN (select XXX...)" clause in Linq to Entities? All the questions I found were regarding a list of objects (IN (1,2,3)) but I want to generate a query with the following syntax: "select * from table1 where field1 not in(select subfield from subtable)" Be aware that this is Linq to Entities and not Linq to Sql... Is it possible? Thanks!

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  • Generate number sequences with LINQ

    - by tanascius
    I try to write a LINQ statement which returns me all possible combinations of numbers (I need this for a test and I was inspired by this article of Eric Lippert). The method's prototype I call looks like: IEnumerable<Collection<int>> AllSequences( int start, int end, int size ); The rules are: all returned collections have a length of size number values within a collection have to increase every number between start and end should be used So calling the AllSequences( 1, 5, 3 ) should result in 10 collections, each of size 3: 1 2 3 1 2 4 1 2 5 1 3 4 1 3 5 1 4 5 2 3 4 2 3 5 2 4 5 3 4 5 Now, somehow I'd really like to see a pure LINQ solution. I am able to write a non LINQ solution on my own, so please put no effort into a solution without LINQ. My tries so far ended at a point where I have to join a number with the result of a recursive call of my method - something like: return from i in Enumerable.Range( start, end - size + 1 ) select BuildCollection(i, AllSequences( i, end, size -1)); But I can't manage it to implement BuildCollection() on a LINQ base - or even skip this method call. Can you help me here?

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  • Which DB? Linq to SQL classes

    - by gadirzade
    Hi. I wont to devolope multiple user supported accounting management aplication in c#.I wont to use linq to sql clases.LINQ to SQL only supports SQL Server/Compact however it is possible the SQLite people have written their own LINQ provider given the name of the assembly.I have to use Db that is FREE.Which DBMS do you prefer to me?

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  • Linq to Sql Data class in dbml

    - by Simon
    I am abit curious about dbml.... Should I create one dbml file for one database or separated into different parts e.g. User dbml (only tables relate to users) etc? When I do this I will have abit of problems. Assume the User dbml has a User table and if the Order dbml has a User table as well, this won't be allowed if the entity namespace are the same. If I have set a different entity namespace for each of the dbml, it works but this will gives me a different entity of User table. When a single data returns to Business Logic layer, there is a difficulty of knowing which entity namespace of the user table to be used. If I built one dbml file instead of having separate dbml, will single dbml appear slower than the separated dbml version when fetching the data from the database.

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  • convert sql to linq sample

    - by Jeroen Breuer
    Hello, I've got a sql statement, but I can't get it working in linq. Can someone show me how I can write the following sql statement as linq? SELECT * FROM mobileApplication LEFT JOIN videoMobile ON mobileApplication.id = videoMobile.mobileApplicationId AND videoMobile.videoId = 257 It's a left join with a where statement on the right table. It works in sql server 2005, but I'd like to write it in linq.

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  • The question about the basics of LINQ to SQL

    - by Alex
    I just started learning LINQ to SQL, and so far I'm impressed with the easy of use and good performance. I used to think that when doing LINQ queries like from Customer in DB.Customers where Customer.Age > 30 select Customer LINQ gets all customers from the database ("SELECT * FROM Customers"), moves them to the Customers array and then makes a search in that Array using .NET methods. This is very inefficient, what if there are hundreds of thousands of customers in the database? Making such big SELECT queries would kill the web application. Now after experiencing how actually fast LINQ to SQL is, I start to suspect that when doing that query I just wrote, LINQ somehow converts it to a SQL Query string SELECT * FROM Customers WHERE Age > 30 And only when necessary it will run the query. So my question is: am I right? And when is the query actually run? The reason why I'm asking is not only because I want to understand how it works in order to build good optimized applications, but because I came across the following problem. I have 2 tables, one of them is Books, the other has information on how many books were sold on certain days. My goal is to select books that had at least 50 sales/day in past 10 days. It's done with this simple query: from Book in DB.Books where (from Sale in DB.Sales where Sale.SalesAmount >= 50 && Sale.DateOfSale >= DateTime.Now.AddDays(-10) select Sale.BookID).Contains(Book.ID) select Book The point is, I have to use the checking part in several queries and I decided to create an array with IDs of all popular books: var popularBooksIDs = from Sale in DB.Sales where Sale.SalesAmount >= 50 && Sale.DateOfSale >= DateTime.Now.AddDays(-10) select Sale.BookID; BUT when I try to do the query now: from Book in DB.Books where popularBooksIDs.Contains(Book.ID) select Book It doesn't work! That's why I think that we can't use thins kinds of shortcuts in LINQ to SQL queries, like we can't use them in real SQL. We have to create straightforward queries, am I right?

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  • Linq To Sql - SQL Default Constraint Problem

    - by Ahmet Altun
    I have a USER table in database. The table has a RegistrationDate column which has a default constraint as GETDATE(). When using LINQ, I don't provide any data for RegistrationDate column to make it default. But SQL Server raises error. I think LINQ tries to insert NULL into the column. How can I make LINQ not to try to insert in the column RegistrationDate, because it has default value?

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  • How to perform Linq select new with datetime in SQL 2008

    - by kd7iwp
    In our C# code I recently changed a line from inside a linq-to-sql select new query as follows: OrderDate = (p.OrderDate.HasValue ? p.OrderDate.Value.Year.ToString() + "-" + p.OrderDate.Value.Month.ToString() + "-" + p.OrderDate.Value.Day.ToString() : "") To: OrderDate = (p.OrderDate.HasValue ? p.OrderDate.Value.ToString("yyyy-mm-dd") : "") The change makes the line smaller and cleaner. It also works fine with our SQL 2008 database in our development environment. However, when the code deployed to our production environment which uses SQL 2005 I received an exception stating: Nullable Type must have a value. For further analysis I copied (p.OrderDate.HasValue ? p.OrderDate.Value.ToString("yyyy-mm-dd") : "") into a string (outside of a Linq statement) and had no problems at all, so it only causes an in issue inside my Linq. Is this problem just something to do with SQL 2005 using different date formats than from SQL 2008? Here's more of the Linq: dt = FilteredOrders.Where(x => x != null).Select(p => new { Order = p.OrderId, link = "/order/" + p.OrderId.ToString(), StudentId = (p.PersonId.HasValue ? p.PersonId.Value : 0), FirstName = p.IdentifierAccount.Person.FirstName, LastName = p.IdentifierAccount.Person.LastName, DeliverBy = p.DeliverBy, OrderDate = p.OrderDate.HasValue ? p.OrderDate.Value.Date.ToString("yyyy-mm-dd") : ""}).ToDataTable(); This is selecting from a List of Order objects. The FilteredOrders list is from another linq-to-sql query and I call .AsEnumerable on it before giving it to this particular select new query. Doing this in regular code works fine: if (o.OrderDate.HasValue) tempString += " " + o.OrderDate.Value.Date.ToString("yyyy-mm-dd");

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  • How to prevent linq-to-sql designer undo my changing

    - by anonim.developer
    Dear All, Thanks for your attention in advance, I’ve met an issue with LINQ-2-SQL designer in VS 2008 SP1 which has made me CRAZY. I use Linq2sql as my DAL. It seems Linq2sql speeds up coding in the first step but lots of issues arise in feature specifically with table or object inheritance. In this case I have a class Entity that all other entity classes generated by Linq2sql designer inherit from. public abstract class Entity { public virtual Guid ID { get; protected set; } } public partial class User : monius.Data.Entity { } And the following generated by L2S designer (DataModel.designer.cs) [Column(Storage = "_ID", AutoSync = AutoSync.OnInsert, DbType = "UniqueIdentifier NOT NULL", IsPrimaryKey = true, IsDbGenerated = true, UpdateCheck = UpdateCheck.Never)] [DataMember(Order = 1)] public System.Guid ID { get { return this._ID; } set { if ((this._ID != value)) { this.OnIDChanging(value); this.SendPropertyChanging(); this._ID = value; this.SendPropertyChanged("ID"); this.OnIDChanged(); } } } When I compile the code VS warns me that Warning 1 'User.ID' hides inherited member 'Entity.ID'. To make the current member override that mplementation, add the override keyword. Otherwise add the new keyword. That warning is obvious and I have to change the code generated by L2S designer (DataModel.designer.cs) to […] public override System.Guid ID { … protected set … } And the code compiled with no error or warning and everyone is happy. But that is not the end of story. As soon as I made changes to entities of the diagram (dbml) or even I open dbml file to view it, any change manually I made to designer has been vanished and POOF! Redo AGAIN. That is a painful job. Now I wonder if there is a way to force L2S designer not changing portions of auto-generated code. I’ll be appreciated if someone kindly helps me with this issue.

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  • use variable within a linq query

    - by jstawski
    take this linq into consideration: list.Where(sil => sil.XML.Element("ticket") != null && sil.XML.Element("ticket").Attribute("id").Value == smsRequestIn.TicketID) if the "ticket" element is not null it searches for it twice and hence is not very effective. Is there a way to use some sort of variables within the linq expression so I can reference the variable instead of doing a double search for the "ticket" element or is linq intelligent enough to not do a double search?

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  • What are some examples of MemberBinding linq expressions?

    - by michielvoo
    There are three possibilities, but I can't find examples: System.Linq.Expressions.MemberAssignment System.Linq.Expressions.MemberListBinding System.Linq.Expressions.MemberMemberBinding I want to write some unit tests to see if I can handle them, but I don't know how to write them except for the first one, which seems to be new Foo { Property = "value" } where Property = "value" is an expression of type MemberAssignment. See also this MSDN article.

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  • How do I programmatically translate a LINQ query to readable English text that correctly describes t

    - by eniac
    I am working on a project that uses Albahari's PredicateBuilder library http://www.albahari.com/nutshell/ to create a linq expression dynamically at run time. I would like to find a way to translate this dynamically created linq predicate of type Expression<Func<T, bool>> into a readable english statement at runtime. I'll give a statically created linq statement as an example: from p in Purchases select p where p.Price 100 && p.Description != "Bike". For this linq statement I would want to dynamically generate at runtime an english description along the lines of: "You are searching for purchases where the price is greater than 100 and the description is not bike". Are there any libraries that already exist which accomplish this goal, keep in mind I am using PredicateBuilder to dynamically generate the where predicate. If no solution exists how would you go about building a solution? Thanks!

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  • LINQ causing my obfuscator to break

    - by JL
    I have the following LINQ that is causing my obfuscator to break. .Where(f => f.FileName == fileName).OrderByDescending(f => f.Position).FirstOrDefault(); Is there another way I could reword this LINQ statement to test against my obfuscator? I've reported the bug, but it could take 1-2 months to fix, so I need to try recode this LINQ in the meantime.

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  • Linq ChangeConflictException occurs when submitting DataContext changes

    - by Alex
    System.Data.Linq.ChangeConflictException: 2 of X updates failed. at System.Data.Linq.ChangeProcessor.SubmitChanges(ConflictMode failureMode) at System.Data.Linq.DataContext.SubmitChanges(ConflictMode failureMode) at PROJECT.Controllers.HomeController.ClickProc(Int32 id, String code, String n) This is what I get very often. This action is done thousands of times a day, and I get this exception about once every 5 seconds. From what I understand it happens when something changes in the database in the period between creating DataContext and updating it. Am I right? How can I fix it? Update I just debugged the error and found the following: Table name: dbo.Stats current value: 9852039 original value: 9852038 database value: 9852039 The Stats table is updated constantly. So how can I still make LINQ save the changes. With "classical" SQL Server access through SqlDataCommand I never had problems like that.

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  • How to deal with the limited Linq Support of OData (Open Data Protocol)

    - by user341127
    I have a software, which uses a lot of Linq to SQL. Recently, I want to immigrate to OData (or WCF Data Service) architecture. But I met too many problems in Linq for the Linq support of OData is so limited. I have to modify most of my Linq statements and test them thoroughly again. I am wondering whether there is a system way to solve such a problem instead of my manual work. For example, by an external package. BTW, now I have no confidence to use OData as a kind of architecture. You are appreciated to share your ideas. Thank you in advance, Ying

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  • The question about the basics of LINQ to SQL working

    - by Alex
    I just started learning LINQ to SQL, and so far I'm impressed with the easy of use and good performance. I used to think that when doing LINQ queries like from Customer in DB.Customers where Customer.Age > 30 select Customer Get all customers from the database ("SELECT * FROM Customers"), move them to the Customers array and then make a search in that Array using .NET methods. This is very inefficient, what if there are hundreds of thousands of customers in the database? Making such big SELECT queries would kill the web application. Now after experiencing how actually fast LINQ to SQL is, I start to suspect that when doing that query I just wrote, LINQ somehow converts it to a SQL Query string SELECT * FROM Customers WHERE Age > 30 And only when necessary it will run the query. So my question is: am I right? And when is the query actually run? The reason why I'm asking is not only because I want to understand how it works in order to build good optimized applications, but because I came across the following problem. I have 2 tables, one of them is Books, the other has information on how many books were sold on certain days. My goal is to select books that had at least 50 sales/day in past 10 days. It's done with this simple query: from Book in DB.Books where (from Sale in DB.Sales where Sale.SalesAmount >= 50 and Sale.DateOfSale >= DateTime.Now.AddDays(-10) select Sale.BookID).Contains(Book.ID) select Book The point is, I have to use the checking part in several queries and I decided to create an array with IDs of all popular books: var popularBooksIDs = from Sale in DB.Sales where Sale.SalesAmount >= 50 and Sale.DateOfSale >= DateTime.Now.AddDays(-10) select Sale.BookID; BUT when I try to do the query now: from Book in DB.Books where popularBooksIDs.Contains(Book.ID) select Book It doesn't work! That's why I think that we can't use thins kinds of shortcuts in LINQ to SQL queries, like we can't use them in real SQL. We have to create straightforward queries, am I right?

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  • time calculation within LINQ

    - by d daly
    Hi I want a linq query to return a calculated timespan, i have used the timespan function before, but im not sure how to incorporate it into linq. Basically the linq is returning a datetime field which i want to subtract from the current datetime to get days and hours. Any help appreciated! Thanks

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  • LINQ version of SQL's LIKE statement

    - by Erwin
    Hi fellow coders I'm new at LINQ, searching the net for LINQ samples that mimic SQL's LIKE statement doesn't satisfy myself. What I want is producing the same query result as this SQL SELECT * FROM table_1 WHERE column_1 LIKE '__0%' I want to query from table_1 where column_1's third character is '0' Is there equivalent statement in LINQ :D thank you

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  • C# + Querying XML with LINQ

    - by user336786
    Hello, I'm learning to use LINQ. I have seen some videos online that have really impressed me. In an effort to learn LINQ myself, I decided to try to write a query to the NOAA web service. If you put "http://www.weather.gov/forecasts/xml/sample_products/browser_interface/ndfdBrowserClientByDay.php?zipCodeList=20001&format=24+hourly&startDate=2010-06-10&numDays=5" in your browser's address bar, you will see some XML. I have successfully retrieved that XML in a C# program. I am loading the XML into a LINQable entity by doing the following: string xml = QueryWeatherService(); XDocument weather = XDocument.Parse(xml); I have a class called DailyForecast defined as follows: public class DailyForecast { public float HighTemperature { get; set; } public float LowTemperature { get; set; } public float PrecipitationPossibility { get; set; } public string WeatherSummary { get; set; } } I'm trying write a LINQ query that adheres to the structure of my DailyForecast class. At this time, I've only gotten to this far: var results = from day in response.Descendants("parameters") select day; Not very far I know. Because of the structure of the XML returned, I'm not sure it is possible to solely use a LINQ query. I think the only way to do this is via a loop and traverse the XML. I'm seeking someone to correct me if I'm wrong. Can someone please tell me if I can get results using purely LINQ that adhere to the structure of the DailyForecast class? If so, how? Thank you!

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  • Open source LINQ search engine for website

    - by Noel
    I want to add a search engine to my website. I want it to handler boolean searches and give me a list of results in order or best match. I need it to be able to work with LINQ, because I want to add additional where clauses to the final query that gets run. I am looking for the best open source .NET search engine that works with LINQ. I like lucene.net but the problem is the LINQ interface (LINQ to Lucene) hasn't been updated since 2008. Are there any good options out there?

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