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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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  • 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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  • 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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  • LINQ nested joins

    - by ace
    Im trying to convert a SQL join to LINQ. I need some help in getting the nested join working in LINQ. This is my SQL query, Ive cut it short just to show the nested join in SQL: LEFT OUTER JOIN dbo.TaskCommentRecipient RIGHT OUTER JOIN dbo.TaskComment ON dbo.TaskCommentRecipient.TaskCommentID = dbo.TaskComment.TaskCommentID ON dbo.Task.Taskid = dbo.TaskComment.TaskCommentTaskId

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  • Search by Letters using LINQ

    - by Biswo
    hi i m using Linq & C# and i want to filter my data as this syntax in Sql Syntax in sql is I hav one table name Customer in which name is field 'Select name from customer where name like 'C%'' can u help to solve this code in Linq

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  • how to specify literal value in linq union

    - by lowlyintern
    I have the following SQL query, note I want the literal value '0' in the second field in the second SELECT statement from the ItemSale table. How do I express this in LINQ? I get the error message 'Invalid anonymous type member declarator'. SELECT BranchNumber,QuantitySold FROM Department UNION SELECT BranchNumber,0 FROM ItemSale How to express the '0' in LINQ? var unionQuery = (from dept in Department select new { dept.BranchNumber, dept.QuantitySold, }) .Concat(from item in ItemSale select new { item.BranchNumber, 0 });

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  • .Net Linq - Join together all item of a List

    - by Melursus
    How can I write a Linq expression that select item from a List and join them together ? Example IList<string> data = new List<string>(); data.Add("MyData1"); data.Add("MyData2"); string result = //some linq query... I try data.Select(x => x + ","); //result = "MyData1, MyData2"

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  • How do linq Last() work?

    - by acidzombie24
    I dont understand how current can be null and last can be an object while last being a LINQ function. I thought last uses GetEnumerator and keeps going until current == null and returns the object. However as you can see the first GetEnumerator().Current is null and last somehow returns an object. How do linq Last() work? var.GetEnumerator().Current var.Last()

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  • Data access layer using Linq to SQL

    - by Andrei Tanasescu
    I am building a c# - linq - sql server winforms/asp.net application, accessing a database. I would like my business logic layer to be easily testable, and that means not littering it with Linq database queries everywhere. What design patterns/ best practices are available for the following use cases - inserting/updating a new object - searching for an object - loading a bunch of related data into a sort of "presentation" object that could be displayed by various views ?

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  • LINQ - joining multiple lists

    - by kristian
    I've looked at the 101 Linq Samples here but I can't see anything like this in that list. If I'm just not seeing a relevant example there, please link to it. If I have these 3 classes: class Student { int id; string name } class Course { int id, string name } class Enrolment { int studentId; int courseId; } How would I use LINQ to get a list of courses a student is enrolled on? (assume I have an IList of all three classes)

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  • Linq to XSD processing

    - by goel
    For Typed Xml to Linq processing ,do i need to download Linq to XSD alpha installer or is it available in VS 2008 ? (I am using VS 2008 Professional edition).

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  • Cast problem with LINQ

    - by yigit
    I'm tring to get my product's types to a list with Linq. var types = (from t in NHibernateSession.Linq<Product>() select t.Type).Distinct().ToList<Type>(); return types; But its giving an Unable to cast object of type error '...Domain.Product' to type '...Domain.Type'. Please tell where am I going wrong.

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  • LINQ to Entites - Left Outer Join - SQL 2000

    - by user255234
    Hi! I'm using Linq to Entities. I have the following query in my code, it includes left outer Join: var surgeonList = (from item in context.T1_STM_Surgeon.Include("T1_STM_SurgeonTitle") .Include("OTER").Include("OSLP") join reptable in context.OSLP on item.Rep equals reptable.SlpCode into surgRepresentative where item.ID == surgeonId select new { ID = item.ID, First = item.First, Last = item.Last, Rep = (surgRepresentative.FirstOrDefault() != null) ? surgRepresentative.FirstOrDefault().SlpName : "N/A", Reg = item.OTER.descript, PrimClinic = item.T1_STM_ClinicalCenter.Name, Titles = item.T1_STM_SurgeonTitle, Phone = item.Phone, Email = item.Email, Address1 = item.Address1, Address2 = item.Address2, City = item.City, State = item.State, Zip = item.Zip, Comments = item.Comments, Active = item.Active, DateEntered = item.DateEntered }) .ToList(); My DEV server has SQL 2008, so the code works just fine. When I moved this code to client's production server - they use SQL 2000, I started getting "Incorrect syntax near '(' ". I've tried changing the ProviderManifestToken to 2000 in my .edmx file, then I started getting "The execution of this query requires the APPLY operator, which is not supported in versions of SQL Server earlier than SQL Server 2005." I tied changing the token to 2005, the "Incorrect syntax near '(' " is back. Can anybody help me to find a workaround for this? Thank you very much in advance!

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  • Should I be learning Linq, Direct SQL Commands (in .net), EF or other?

    - by Wil
    Basically, I have a very good knowledge of plain old SQL coming from Classic ASP programming. Over the past couple of months, I have been learning C# and today was my first full day at MVC 3 (Razor) which I am loving! I need to get back in to Databases and I know that writing SqlCommand everywhere is obviously outdated (although it is nice I can still do it!). I used to go to a great usergroup as an IT Pro and the developer stuff went completely over my head, however I do remember a few things which kept coming up such as LINQ... However, that was some time ago and now the same people on Twitter are saying how out dated it is. I have tried to do research on both and I am clueless as to what direction I should go in, or when to use one over another (if learning both is a good thing). I am more so confused as I thought EF was a part of the .Net Framework, however, reading through the quick start guide, I had to download a component using Nuget. ... Basically I am out of my depth here and just need some honest advice of where to go!

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  • LINQ to Entity, using a SQL LIKE operator

    - by Mario
    I have a LINQ to ENTITY query that pulls from a table, but I need to be able to create a "fuzzy" type search. So I need to add a where clause that searches by lastname IF they add the criteria in the search box (Textbox, CAN be blank --- in which case it pulls EVERYTHING). Here is what I have so far: var query = from mem in context.Member orderby mem.LastName, mem.FirstName select new { FirstName = mem.FirstName, LastName = mem.LastName, }; That will pull everything out of the Member table that is in the Entity object. Then I have an addition to the logic: sLastName = formCollection["FuzzyLastName"].ToString(); if (!String.IsNullOrEmpty(sLastName)) query = query.Where(ln => ln.LastName.Contains(sLastName)); The problem is when the search button is pressed, nothing is returned (0 results). I have run the query against the SQL Server that I expect to happen here and it returns 6 results. This is the query I expect: SELECT mem.LastName, mem.FirstName FROM Members mem WHERE mem.LastName = 'xxx' (when xxx is entered into the textbox) Anyone see anything wrong with this?

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  • Use CompiledQuery.Compile to improve LINQ to SQL performance

    - by Michael Freidgeim
    After reading DLinq (Linq to SQL) Performance and in particular Part 4  I had a few questions. If CompiledQuery.Compile gives so much benefits, why not to do it for all Linq To Sql queries? Is any essential disadvantages of compiling all select queries? What are conditions, when compiling makes whose performance, for how much percentage? World be good to have default on application config level or on DBML level to specify are all select queries to be compiled? And the same questions about Entity Framework CompiledQuery Class. However in comments I’ve found answer  of the author ricom 6 Jul 2007 3:08 AM Compiling the query makes it durable. There is no need for this, nor is there any desire, unless you intend to run that same query many times. SQL provides regular select statements, prepared select statements, and stored procedures for a reason.  Linq now has analogs. Also from 10 Tips to Improve your LINQ to SQL Application Performance   If you are using CompiledQuery make sure that you are using it more than once as it is more costly than normal querying for the first time. The resulting function coming as a CompiledQuery is an object, having the SQL statement and the delegate to apply it.  And your delegate has the ability to replace the variables (or parameters) in the resulting query. However I feel that many developers are not informed enough about benefits of Compile. I think that tools like FxCop and Resharper should check the queries  and suggest if compiling is recommended. Related Articles for LINQ to SQL: MSDN How to: Store and Reuse Queries (LINQ to SQL) 10 Tips to Improve your LINQ to SQL Application Performance Related Articles for Entity Framework: MSDN: CompiledQuery Class Exploring the Performance of the ADO.NET Entity Framework - Part 1 Exploring the Performance of the ADO.NET Entity Framework – Part 2 ADO.NET Entity Framework 4.0: Making it fast through Compiled Query

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  • LINQ - Select Statement - The null value cannot be assigned to a member with type System.Int32 which

    - by thiag0
    I am trying to achieve the following... _4S.NJB_Request request = (from r in db.NJB_Requests where r.RequestId == referenceId select r).Take(1).SingleOrDefault(); Getting the following exception... Message: The null value cannot be assigned to a member with type System.Int32 which is a non-nullable value type. StackTrace: at System.Data.Linq.SqlClient.SqlProvider.Execute(Expression query, QueryInfo queryInfo, IObjectReaderFactory factory, Object[] parentArgs, Object[] userArgs, ICompiledSubQuery[] subQueries, Object lastResult) at System.Data.Linq.SqlClient.SqlProvider.ExecuteAll(Expression query, QueryInfo[] queryInfos, IObjectReaderFactory factory, Object[] userArguments, ICompiledSubQuery[] subQueries) at System.Data.Linq.SqlClient.SqlProvider.System.Data.Linq.Provider.IProvider.Execute(Expression query) at System.Data.Linq.DataQuery`1.System.Linq.IQueryProvider.Execute[S](Expression expression) at System.Linq.Queryable.SingleOrDefault[TSource](IQueryable`1 source) at DAL.SqlDataProvider.MarkNJBPCRequestAsComplete(Int32 referenceId, Int32 processState) I have verified that 'referenceId' does have a value. Anyone know why this would happen in a select statement? Thanks!

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  • Linq to SQL and concurrency with Rob Conery repository pattern

    - by David Hall
    I have implemented a DAL using Rob Conery's spin on the repository pattern (from the MVC Storefront project) where I map database objects to domain objects using Linq and use Linq to SQL to actually get the data. This is all working wonderfully giving me the full control over the shape of my domain objects that I want, but I have hit a problem with concurrency that I thought I'd ask about here. I have concurrency working but the solution feels like it might be wrong (just one of those gitchy feelings). The basic pattern is: private MyDataContext _datacontext private Table _tasks; public Repository(MyDataContext datacontext) { _dataContext = datacontext; } public void GetTasks() { _tasks = from t in _dataContext.Tasks; return from t in _tasks select new Domain.Task { Name = t.Name, Id = t.TaskId, Description = t.Description }; } public void SaveTask(Domain.Task task) { Task dbTask = null; // Logic for new tasks omitted... dbTask = (from t in _tasks where t.TaskId == task.Id select t).SingleOrDefault(); dbTask.Description = task.Description, dbTask.Name = task.Name, _dataContext.SubmitChanges(); } So with that implementation I've lost concurrency tracking because of the mapping to the domain task. I get it back by storing the private Table which is my datacontext list of tasks at the time of getting the original task. I then update the tasks from this stored Table and save what I've updated This is working - I get change conflict exceptions raised when there are concurrency violations, just as I want. However, it just screams to me that I've missed a trick. Is there a better way of doing this? I've looked at the .Attach method on the datacontext but that appears to require storing the original version in a similar way to what I'm already doing. I also know that I could avoid all this by doing away with the domain objects and letting the Linq to SQL generated objects all the way up my stack - but I dislike that just as much as I dislike the way I'm handling concurrency.

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