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  • linq-to-sql combine child expressions

    - by VictorS
    I need to create and combine several expressions for child entity into one to use it on "Any" operator of a parent. Code now looks like this: Expresion<Child, bool> startDateExpression = t => t.start_date >= startDate; Expression<Child, bool> endDateExpression = t => t.end_date <= endDate; .... ParameterExpression param = startDateExpression.Parameters[0]; Expression<Func<T, bool>> Combined = Expression.Lambda<Func<Child, bool>>( Expression.AndAlso(startDateExpression.Body, startDateExpression.Body), param); //but now I am trying to use combined expression on parent //this line fails just to give an idea on what I am trying to do: //filter type is IQueryable<Parent>; var filter = filter.Where(p =>p.Children.Any(Combined)); How can I do that? Is there better(more elegant way way of doing it?

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  • Linq to SQL ordered child collection

    - by Matt Connolly
    Is there a way to define a default order column from a child collection? In my case, I have a Form entity that has a collection of FormItem entities called FormItems. FormItem has a property called DisplayOrder (int). I want to make sure that any Form entities I return from a method have that collection properly ordered. Is there a way to do this before returning the result? For example, I tried this but the list is not actually sorted: var form = context.Forms.FirstOrDefault(x => x.IsDeleted == false && x.FormName == formName); if (form != null) { form.FormItems.OrderBy(x => x.DisplayOrder); // I can't even figure out a way to cast this next line so that it will compile // form.FormItems = form.FormItems.OrderBy(x => x.DisplayOrder); } return form; Is there a way to do this without using DataLoadOptions?

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  • LINQ If .Any matches .Any

    - by molgan
    Hello I have 2 string arrays, and I would like to return if any of them exists in _authRole array. How is that done? string[] _userRoles = userdata.Split(','); string[] _authRoles = AuthRoles.Split(','); bool isAuthorized = _authRoles.Any(_userRoles ??); /M

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  • LINQ to Objects .Distinct() not pulling distinct objects

    - by Anthony Potts
    I have two ways that I am doing a fuzzy search for a customer. One is by an abbreviated name and the other is by the customers full name. When I take these two and then union them together (which I have read several places should remove distinct values) I get duplicates. Thinking that all I need to do is then call the .Distinct() method on this I also still get Duplicates. Do I need to implement some compare functionality in my customer object? My code: Dim shortNameMatch As List(Of ICustomer) = CustomerLibrary.GetCustomersByShortName(term) Dim custNameMatch As List(Of ICustomer) = CustomerLibrary.GetCustomersByCustName(term) Dim allMatch = (From a In (From s In shortNameMatch Select s).Union(From c In custNameMatch Select c) Select a).Distinct()

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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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  • 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 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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  • 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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  • 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 "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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  • 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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  • 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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  • 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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  • 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 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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  • 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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  • Return an empty collection when Linq where returns nothing

    - by ahsteele
    I am using the below statement with the intent of getting all of the machine objects from the MachineList collection (type IEnumerable) that have a MachineStatus of i. The MachineList collection will not always contain machines with a status of i. At times when no machines have a MachineStatus of i I'd like to return an empty collection. My call to ActiveMachines (which is used first) works but InactiveMachines does not. public IEnumerable<Machine> ActiveMachines { get { return Customer.MachineList .Where(m => m.MachineStatus == "a"); } } public IEnumerable<Machine> InactiveMachines { get { return Customer.MachineList .Where(m => m.MachineStatus == "i"); } } Edit Upon further examination it appears that any enumeration of MachineList will cause subsequent enumerations of MachineList to throw an exeception: Object reference not set to an instance of an object. Therefore, it doesn't matter if a call is made to ActiveMachines or InactiveMachines as its an issue with the MachineList collection. This is especially troubling because I can break calls to MachineList simply by enumerating it in a Watch before it is called in code. At its lowest level MachineList implements NHibernate.IQuery being returned as an IEnumerable. What's causing MachineList to lose its contents after an initial enumeration?

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  • LINQ Join 2 List<T>s

    - by David Murdoch
    Preface: I don't understand what this does: o => o.ID, i => i.ID, (o, id) => o So go easy on me. :-) I have 2 lists that I need to join together: // contains ALL contacts for a customer. // Each item has a unique ID. // There are no duplicates. ContactCollection list1 = myCustomer.GetContacts(); // contains the customer contacts (in list1) relevant to a REPORT // the items in this list may have properties that differ from those in list1. /*****/// e.g.: /*****/ bool SelectedForNotification; /*****/// may be different. ContactCollection list2 = myReport.GetContacts(); I need to create a third ContactCollection that contains all of the contacts in list1 but with the properties of the items in list2, if they are there (list3.Count == list1.Count). I feel as though I'm not making any sense. So, please ask questions in the comments and I'll try to clarify.

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  • substring with linq??

    - by phenevo
    I've got collection of words, and i wanna create collection from this collection limited to 5 chars Input: Car Collection Limited stackoverflow Output: car colle limit stack word.Substring(0,5) throws exception (length) word.Take(10) is not good idea, too... Any good ideas ??

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  • Using LINQ to remove dupicates in dictionary and the count of those duplicates

    - by Robert
    I have some code that returns unique elements in my dictionary, but I would also like to return the count of the duplicate elements. Basically change dictionary[key, uniqueelement] to dictionary[uniqueelement, count]. Here is my code that just returns the unique elements. var uniqueItems = deviceInstances.Children.GroupBy(pair => pair.Value.Information.UnderlyingDeviceType) .Select(group => group.First()) .ToDictionary(pair => pair.Key, pair => pair.Value.Information.UnderlyingDeviceType.ToString());

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  • Referencing object's identity before submitting changes in LINQ

    - by Axarydax
    Hi, is there a way of knowing ID of identity column of record inserted via InsertOnSubmit beforehand, e.g. before calling datasource's SubmitChanges? Imagine I'm populating some kind of hierarchy in the database, but I wouldn't want to submit changes on each recursive call of each child node (e.g. if I had Directories table and Files table and am recreating my filesystem structure in the database). I'd like to do it that way, so I create a Directory object, set its name and attributes, then InsertOnSubmit it into DataContext.Directories collection, then reference Directory.ID in its child Files. Currently I need to call InsertOnSubmit to insert the 'directory' into the database and the database mapping fills its ID column. But this creates a lot of transactions and accesses to database and I imagine that if I did this inserting in a batch, the performance would be better. What I'd like to do is to somehow use Directory.ID before commiting changes, create all my File and Directory objects in advance and then do a big submit that puts all stuff into database. I'm also open to solving this problem via a stored procedure, I assume the performance would be even better if all operations would be done directly in the database.

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