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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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  • Converting HTML to its safe entities with Javascript

    - by James P
    I'm trying to convert characters like < and > into &lt; and &gt; etc. User input is taken from a text box, and then copied into a DIV called changer. here's my code: function updateChanger() { var message = document.getElementById('like').value; message = convertHTML(message); document.getElementById('changer').innerHTML = message; } function convertHTML(input) { input = input.replace('<', '&lt;'); input = input.replace('>', '&gt;'); return input; } But it doesn't seem to replace >, only <. Also tried like this: input = input.replace('<', '&lt;').replace('>', '&gt;'); But I get the same result. Can anyone point out what I'm doing wrong here? Cheers.

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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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  • Instantiating a context in LINQ to Entities

    - by Jagd
    I've seen two different manners that programmers approach when creating an entity context in their code. The first is like such, and you can find it all over the MSDN code examples: public void DoSomething() { using TaxableEducationEntities context = new TaxableEducationEntities()) { // business logic and whatever else } } The second is to create the context as a private attribute in some class that encapsulates your business logic. So you would have something like: public class Education_LINQ { private TaxableEducationEntities context = new TaxableEducationEntities(); public void DoSomething() { var result = from a in context.luAction select a; // business logic and whatever else } } Which way is more efficient? Assume that you have two methods, one called DoSomething1() and another called DoSomething2(), and both methods incorporate the using statement to open the context and do whatever with it. Were you to call one method after the other, would there be any superfluous overhead going on, since essentially both methods create the context and then clean it up when they're done? As opposed to having just one private attribute that is created when a class object is instantiated, and then in turn cleaned up when the object goes out of scope?

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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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  • LINQ To Entities - Items, ItemCategories & Tags

    - by Simon
    Hi There, I have an Entity Model that has Items, which can belong to one or more categories, and which can have one or more tags. I need to write a query that finds all tags for a given ItemCategory, preferably with a single call to the database, as this is going to get called fairly often. I currently have: Dim q = (From ic In mContext.ItemCategory _ Where ic.CategoryID = forCategoryID _ Select ic).SelectMany(Function(cat) cat.Items).SelectMany(Function(i) i.Tags) _ .OrderByDescending(Function(t) t.Items.Count).ToList This is nearly there, apart from it doesn't contain the items for each tag, so I'd have to iterate through, loading the item reference to find out how many items each tag is related to (for font sizing). Ideally, I want to return a List(Of TagCount), which is just a structure, containing Tag as string, and Count as integer. I've looked at Group and Join, but I'm not getting anywhere so any help would be greatly appreciated!

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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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  • Entity Framework, what's so bad and what's so good?

    - by AverageJoe719
    Hi all, I am curious as to what your opinions are in Entity Framework? I have read some things like the first version of it is super horrible because it doesn't handle many to many relationships (though many ORMs don't and I've never seen the issue with just making a linking table). Also is LINQ to Entities the same as Entity Framework? I think it is, but it seems like one term is used or the other. I have used Linq to SQL before, what are the advantages of it compared to that? In terms of coding preference I like to build everything from the ground up so I can fully understand it/be in control of the code I write. So I have heard that Entity Framework is harder and I know LinqToSQL handles a lot of stuff automatically, but specifically what are the differences? I appreciate your responses, Thanks =)

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  • Linq-to-Entities Left JOIN

    - by shivesh
    This is my query: from forum in Forums join post in Posts on forum equals post.Forum into postGroup from p in postGroup where p.ParentPostID==0 select new { forum.Title, forum.ForumID, LastPostTitle = p.Title, LastPostAddedDate = p.AddedDate }).OrderBy(o=>o.ForumID) Currently the Join is not left join, meaning if some forum doesn't have a post that belongs to it, it will not be returned. The forum without posts must be returned with null (or default) values for the post properties.

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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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