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  • SQL Like keyword in Dynamic Linq

    - by Erwin
    Hi fellow programmer I want to use SQL's Like keyword in dynamic LINQ. The query that I want to make is like this select * from table_a where column_a like '%search%' Where the column_a can be dynamically changed to other column etc In this dynamic LINQ var result = db.table_a.Where( a=> (a.column_a.Contains("search")) ); But the column can't be dynamically changed , only the search key can How do we create a dynamic LINQ like var result = db.table_a.Where("column_a == \"search\""); That we can change the column and the search key dynamically

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  • What Sorting Algorithm Is Used By LINQ "OrderBy"?

    - by Mystagogue
    Evidently LINQ's "OrderBy" had originally been specified as unstable, but by the time of Orca it was specified as stable. Not all documentation has been updated accordingly - consider these links: Jon Skeet on OrderBy stability Troy Magennis on OrderBy stability But if LINQ's OrderBy is now "stable," then it means it is not using a quicksort (which is inherently unstable) even though some documentation (e.g. Troy's book) says it is. So my question is: if not quicksort, then what is the actual algorithm LINQ's orderBy is using?

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  • Exception while trying to reference LINQ namespace

    - by MarceloRamires
    While trying to use linq in a .NET 2.0 winforms project I got: Namespace or type specified in the Imports 'System.Linq' doesn't contain any public member or cannot be found. Make sure the namespace or the type is defined and contains at least one public member. Make sure the imported element name doesn't use any aliases In both the lines that reference the following namespaces: System.Linq; System.Xml.Linq; How could I get these namespaces to work on .NET 2.0 without referencing an external DLL or anything ?

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  • LINQ InsertOnSubmit Required Fields needed for debugging

    - by Derek Hunziker
    Hi All, I've been using the ADO.NET Strogly-Typed DataSet model for about 2 years now for handling CRUD and stored procedure executions. This past year I built my first MVC app and I really enjoyed the ease and flexibility of LINQ. Perhaps the biggest selling point for me was that with LINQ I didn't have to create "Insert" stored procedures that would return the SCOPE_IDENTITY anymore (The auto-generated insert statements in the DataSet model were not capable of this without modification). Currently, I'm using LINQ with ASP.NET 3.5 WebForms. My inserts are looking like this: ProductsDataContext dc = new ProductsDataContext(); product p = new product { Title = "New Product", Price = 59.99, Archived = false }; dc.products.InsertOnSubmit(p); dc.SubmitChanges(); int productId = p.Id; So, this product example is pretty basic, right, and in the future, I'll probably be adding more fields to the database such as "InStock", "Quantity", etc... The way I understand it, I will need to add those fields to the database table and then delete and re-add the tables to the LINQ to SQL Class design view in order to refresh the DataContext. Does that sound right? The problem is that any new fields that are non-null are NOT caught by the ASP.NET build processes. For example, if I added a non-null field of "Quantity" to the database, the code above would still build. In the DataSet model, the stored procedure method would accept a certain amount of parameters and would warn me that my Insert would fail if I didn't include a quantity value. The same goes for LINQ stored procedure methods, however, to my knowledge, LINQ doesn't offer a way to auto generate the insert statements and that means I'm back to where I started. The bottom line is if I used insert statements like the one above and I add a non-null field to my database, it would break my app in about 10-20 places and there would be no way for me to detect it. Is my only option to do a solution-side search for the keyword "products.InsertOnSubmit" and make sure the new field is getting assigned? Is there a better way? Thanks!

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  • Hierarchical data in Linq - options and performance

    - by Anthony
    I have some hierarchical data - each entry has an id and a (nullable) parent entry id. I want to retrieve all entries in the tree under a given entry. This is in a SQL Server 2005 database. I am querying it with LINQ to SQL in C# 3.5. LINQ to SQL does not support Common Table Expressions directly. My choices are to assemble the data in code with several LINQ queries, or to make a view on the database that surfaces a CTE. Which option (or another option) do you think will perform better when data volumes get large? Is SQL Server 2008's HierarchyId type supported in Linq to SQL?

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  • How to use Linq in Mono?

    - by Jader Dias
    I can't make System.Linq (aka. Linq-to-objects) work. I am running MonoDevelop 2.2.1 in Ubuntu 10 Lucid Lynx with Mono 2.4.4. They advertise in their site that they implemented Linq, but I can't even find Enumerable.Range or .ToArray(). What's wrong?

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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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  • 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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  • Entity Framework vs LINQ to SQL

    - by Chris Roberts
    Now that .NET v3.5 SP1 has been released (along with VS2008 SP1), we now have access to the .NET entity framework. My question is this. When trying to decide between using the Entity Framework and LINQ to SQL as an ORM, what's the difference? The way I understand it, the Entity Framework (when used with LINQ to Entities) is a 'big brother' to LINQ to SQL? If this is the case - what advantages does it have? What can it do that LINQ to SQL can't do on its own?

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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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  • 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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