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  • C# LINQ: Join and Group

    - by Soo
    I have two tables TableA aId aValue TableB bId aId bValue I want to join these two tables via aId, and from there, group them by bValue var result = from a in db.TableA join b in db.TableB on a.aId equals b.aId group b by b.bValue into x select new {x}; My code doesn't recognize the join after the group. In other words, the grouping works, but the join doesn't (or at least I can't figure out how to access all of the data after the join). Any help would be appreciated. I'm a n00b.

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  • VB.NET LINQ to SQL Delete All Records

    - by Daniel
    I am having problems with deleting all records in a table with VB.NET. I am using this code to delete all records in the Contacts table For Each contact In database.Contacts database.Contacts.DeleteOnSubmit(contact) Next But I get this error Can't perform Create, Update or Delete operations on 'Table(Contact)' because it has no primary key. Anyone have any suggestions? Thanks

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  • linq null refactoring code

    - by user276640
    i have code public List<Files> List(int? menuId) { if (menuId == null) { return _dataContext.Files.ToList(); } else { return _dataContext.Files.Where(f => f.Menu.MenuId == menuId).ToList(); } } is it possible to make it only one line like return _dataContext.Files.Where(f = f.Menu.MenuId == menuId).ToList();?

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  • Linq SqlMethods.Like fails

    - by Russell Steen
    I'm following the tips here, trying to leverage the statement that the sql doesn't get created until the enumerator is tripped. However I get the following error on the code below. I'm using Linq2Entities, not linq2sql. Is there a way to do this in Linq2entities? Method 'Boolean Like(System.String, System.String)' cannot be used on the client; it is only for translation to SQL. query = db.MyTables.Where(x => astringvar.Contains(x.Field1)); if (!String.IsNullOrEmpty(typeFilter)) { if (typeFilter.Contains('*')) { typeFilter = typeFilter.Replace('*', '%'); query = query.Where(x=> SqlMethods.Like(x.Type, typeFilter)); } else { query = query.Where(x => x.Type == typeFilter); } }

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  • No output from Linq to XML

    - by Gogster
    Hi all, I have the following code: protected void Page_Load(object sender, EventArgs e) { XElement xml = XElement.Load(Server.MapPath("ArenasMembers.xml")); var query = from p in xml.Descendants("members") select new { Name = p.Element("name").Value, Email = p.Attribute("email").Value }; foreach (var member in query) { Response.Write("Employee: " + member.Name + " " + member.Email + "<br />"); } } Which, using the hover information in Visual Studio, is reading the XNL file in correctly, however the foreach is not outputting any of the records. XML: <?xml version="1.0" encoding="utf-8" ?> <members> <member> <arena>EAA Office</arena> <memberid>1</memberid> <name>Jane Doe</name> <email>[email protected]</email> </member> <member> <arena>EAA Office</arena> <memberid>2</memberid> <name>John Bull</name> <email>[email protected]</email> </member> <member> <arena>O2 Arena</arena> <memberid>3</memberid> <name>John Doe</name> <email>[email protected]</email> </member> <member> <arena>O2 Arena</arena> <memberid>4</memberid> <name>Bernard Cribbins</name> <email>[email protected]</email> </member> <member> <arena>Colourline Arena</arena> <memberid>5</memberid> <name>John Bon Jovi</name> <email>[email protected]</email> </member> <member> <arena>NIA</arena> <memberid>6</memberid> <name>Rhianna</name> <email>[email protected]</email> </member> </members> Can you see what is wrong?

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  • Odd Linq behavior with IList / IEnumerable

    - by Aren B
    I've got the following code: public IList<IProductViewModel> ChildProducts { get; set; } public IList<IProductViewModel> GiftItems { get; set; } public IList<IProductViewModel> PromoItems { get; set; } public IList<IProductViewModel> NonGiftItems { get { return NonPromoItems.Except(GiftItems, new ProductViewModelComparer()).ToList(); } } public IList<IProductViewModel> NonPromoItems { get { return ChildProducts.Where(p => !p.IsPromotion).ToList(); } } So basically, NonPromoItems is (ChildProducts - PromoItems) and NonGiftItems is (NonPromoItems - GiftItems) However When: ChildProducts = IEnumerable<IProductViewModel>[6] PromoItems = IEnumerable<IProductViewModel>[1] where item matches 1 item in ChildProducts GiftItems = IEnumerable<IProductViewModel>[0] My Result is NonPromoItems = IEnumerable<IProductViewModel>[5] This is Correct NonGiftItems = IEnumerable<IProductViewModel>[4] This is Incorrect Somehow an Except(...) is removing an item when given an empty list to subtract. Any ideas anyone?

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  • How to use Linq to group DateTime by month and days calculation

    - by Daoming Yang
    Hi all, I have two questions: First one: I have a order list and want to group them by the created month for the reports. Each order's created datetime will be like "2010-03-13 11:17:16.000" How can I make them only group by date like "2010-03"? Note: the DateCreated is the DateTime tpye The following code is not correct. var items = orderList.GroupBy(t => t.DateCreated.Month) .Select(g => new Order() { DateCreated = g.Key }) .OrderByDescending(x => x.OrderID).ToList(); Second one: Output the full months between two dates in C# If an user choose 2010-04-08 and 2010-06-04, I want to output the 2010-04-01 and 2010-06-30. I can always get the first day and last day of the months, but I want to find out some other options Many thanks. Many thanks.

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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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  • Compiled Linq Queries with Built-in SQL functions

    - by Brandi
    I have a query that I am executing in C# that is taking way too much time: string Query = "SELECT COUNT(HISTORYID) FROM HISTORY WHERE YEAR(CREATEDATE) = YEAR(GETDATE()) "; Query += "AND MONTH(CREATEDATE) = MONTH(GETDATE()) AND DAY(CREATEDATE) = DAY(GETDATE()) AND USERID = '" + EmployeeID + "' "; Query += "AND TYPE = '5'"; I then use SqlCommand Command = new SqlCommand(Query, Connection) and SqlDataReader Reader = Command.ExecuteReader() to read in the data. This is taking over a minute to execute from C#, but is much quicker in SSMS. I see from google searching you can do something with CompiledQuery, but I'm confused whether I can still use the built in SQL functions YEAR, MONTH, DAY, and GETDATE. If anyone can show me an example of how to create and call a compiled query using the built in functions, I will be very grateful! Thanks in advance.

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  • LINQ "table" variable

    - by Cat
    I'm trying to turn a method I have right now into a more "generic" method that returns a string. Right now, the method uses a statement like this: var app = (from d in testContext.DAPPs where d.sserID == (Guid)user.ProviderUserKey select d).ToList(); I process the results of "app", add extra text etc. The piece that changes (that I need to make more "generic") is the table name (DAPPs). Is there a way I can do that, or, a better way to go around this all together?

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  • DBnull in Linq query causing problems

    - by nat
    hi there i am doing a query thus: int numberInInterval = (from dsStatistics.J2RespondentRow item in jStats.J2Respondent where item.EndTime > dtIntervalLower && item.EndTime <= dtIntervalUpper select item).count(); there appear to be some dbnulls in the endtime column.. any way i can avoid these? tried adding && where item.endtime != null.. and even != dbnull.value do i have to do a second (first) query to grab all that arent null then run the above one? im sure its super simple fix, but im still missing it.. as per thanks nat

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  • Linq To Sql: Compiled Queries and Extension Methods

    - by Beni
    Hi community, I'm interessted, how does Linq2Sql handles a compiled query, that returns IQueryable. If I call an extension method based on a compiled query like "GetEntitiesCompiled().Count()" or "GetEntitiesCompiled().Take(x)". What does Linq2Sql do in the background? This would be very bad, so in this situation I should write a compiled query like "CountEntitiesCompiled". Does he load the result (in this case "GetEntitiesCompiled()") into the memory (mapped to the entity class like "ToList()")? So what situations make sense, when the compiled queries return IQueryable, that query is not able to modify, before request to the Sql-Server. So in my opinion I can just as good return List. Thanks for answers!

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  • 'And' operator in Linq

    - by Ani
    I have a query that prints userid in label1 when username is entered.Works fine; but i want to write query for username and password that prints userid. so how can i write it? i tried writing using 'and' operator but dont seems to work. int id = (from auser in lq.logins where auser.username == userNameString //&& auser.Password =pwdString select auser.userid).SingleOrDefault(); label1.Text = id.ToString(); Thanks Ani

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  • Why LINQ will work this way?

    - by Benny
    public static ArrayList GetStudentAsArrayList() { ArrayList students = new ArrayList { new Student() { RollNumber = 1,Name ="Alex " , Section = 1 ,HostelNumber=1 }, new Student() { RollNumber = 2,Name ="Jonty " , Section = 2 ,HostelNumber=2 }, }; return students; } this doesn't compile: ArrayList is not IEnumerable ArrayList lstStudents = GetStudentAsArrayList(); var res = from r in lstStudents select r; but this will compile: ArrayList lstStudents = GetStudentAsArrayList(); var res = from Student r in lstStudents select r; Can anybody explain? what's the magic here?

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  • Using Multiple Foreign Keys to the same table in LINQ

    - by Graeme
    I have a table Users and a table Items In the Items table, I have fields such as ModifiedBy CreatedBy AssignedTo which all have a userId integer. The database is set up to have these as foreign keys back to the Users table. When using LINQToSQL, the relationships which are automatically built from the dbml end up giving me names like User, User1 and User2 e.g. myItem.User1.Name or myItem.User2.Name Obviously this isn't very readable and I'd like it be along the lines of myItem.CreatedByUser.Name or myItem.ModifiedByUser.Name etc I could change the names of the relationships but that means I have to redo that every time I change the db schema and refresh the dbml. Is there any way round this?

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  • Linq 2 SQL Store inherited classes - not mapped to tables in the database

    - by user348672
    Hi. I'm trying to introduce the Linq2SQL technique into the project and have encountered the following issue: I've created ORM classes based on the Northwind database. In some other application I create several classes derived from the Linq2SQL classes. I'm able to add such a class to EntitySet but the application fails to submit changes. Is there any way around this? Sample code(MyClass is derived from the Order): DataClasses1DataContext northwind = new DataClasses1DataContext(); Product chai = northwind.Products.Single(p => p.ProductName == "Chai"); Product tofu = northwind.Products.Single(p => p.ProductName == "Tofu"); Order myOrder = new Order(); myOrder.OrderDate = DateTime.Now; myOrder.RequiredDate = DateTime.Now.AddDays(1); myOrder.Freight = 34; Order_Detail myItem1 = new Order_Detail(); myItem1.Product = chai; myItem1.Quantity = 12345; Order_Detail myItem2 = new Order_Detail(); myItem2.Product = tofu; myItem2.Quantity = 3; myOrder.Order_Details.Add(myItem1); myOrder.Order_Details.Add(myItem2); Customer myCustomer = northwind.Customers.Single(c => c.CompanyName == "B's Beverages"); MyClass newOrder = new MyClass(); newOrder.OrderDate = DateTime.Now; newOrder.RequiredDate = DateTime.Now.AddDays(31); newOrder.Freight = 35; Order_Detail myItem3 = new Order_Detail(); myItem3.Product = tofu; myItem3.Quantity = 3; newOrder.Order_Details.Add(myItem3); myCustomer.Orders.Add(myOrder); myCustomer.Orders.Add(newOrder); As I said I'm able to add the newOrder object but unable to submit into the database.

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  • Which LINQ query is more effective?

    - by Danny Chen
    I have a huge IEnumerable(suppose the name is myItems), which way is more effective? Solution 1: Filter it first then ForEach. Array.ForEach(myItems.Where(FILTER-IT-HERE).ToArray(),MY-ACTION); Solution 2: Do RETURN in MY-ACTION if the item is not up to the mustard. Array.ForEach(myItems.ToArray(),MY-ACTION-WITH-FILTER); Is one of them always better than another? Or any other good suggestions? Thanks in advance.

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  • What's FirstOrDefault for DateTime in Linq?

    - by Keltex
    If I have a query that returns a DateTime, what's the value of FirstOrDefault? Is there a generic way to get the default value of a C# scalar? Example: var list = (from item in db.Items where item.ID==1234 select item.StartDate).FirstOrDefault(); Edit: Assume that the column StartDate can't be null.

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  • linq null parameter

    - by kusanagi
    how can i do the code static string BuildMenu(List<Menu> menu, int? parentId) { foreach (var item in menu.Where(i => i.ParentMenu == parentId || i.ParentMenu.MenuId == parentId).ToList()) { } } return BuildMenu(menuList,null); so if parentId==null then return only records i = i.ParentMenu == null but when parentId is 0 then return records with i.ParentMenu.MenuId == parentId

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  • using Linq to partition data into arrays

    - by user200295
    I have an array of elements where the element has a Flagged boolean value. 1 flagged 2 not flagged 3 not flagged 4 flagged 5 not flagged 6 not flagged 7 not flagged 8 flagged 9 not flagged I want to break it into arrays based on the flagged indicator output array 1 {1,2,3} array 2 {4,5,6,7} array 3 {8,9}

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  • linq selecting into custom object

    - by user276640
    what is wrong with such code public List<SearchItem> Search(string find) { return (from i in _dataContext.News where i.Text.Contains(find) select new SearchItem { ControllerAction = "test", id = i.Id.ToString(), LinkText = "test" }).ToList(); } public struct SearchItem { public string ControllerAction; public string LinkText; public string id; }

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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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  • LINQ to XML Query Help

    - by cw
    Hello, I am trying to get a "diff" of 2 xml documents and end up with a list of Elements that are different. Below is the XML, I was wondering if anyone can assist. In the case below, I want the list to contain the "file2.xml" element and the "file3.xml" element because they are both different or new than the first xml document. Thanks in advance! <?xml version="1.0" encoding="utf-8" ?> <versioninfo> <files> <file version="1.0">file1.xml</file> <file version="1.0">file2.xml</file> </files> </versioninfo> <?xml version="1.0" encoding="utf-8" ?> <versioninfo> <files> <file version="1.0">file1.xml</file> <file version="1.1">file2.xml</file> <file version="1.0">file3.xml</file> </files> </versioninfo>

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  • LINQ to SQL repository - caching data

    - by creativeincode
    I have built my first MVC solution and used the repository pattern for retrieving/inserting/updating my database. I am now in the process of refactoring and I've noticed that a lot of (in fact all) the methods within my repository are hitting the database everytime. This seems overkill and what I'd ideally like is to do is 'cache' the main data object e.g. 'GetAllAdverts' from the database and to then query against this cached object for things like 'FindAdvert(id), AddAdvert(), DeleteAdvert() etc..' I'd also need to consider updating/deleting/adding records to this cache object and the database. What is the best apporoach for something like this? My knowledge of this type of things is minimal and really looking for advice/guidance/tutorial to point me in the right direction. Thanks in advance.

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