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• How to aggregate over few types with linq?

  - by Shimmy

  Can someone help me translate the following to one liner: Dim items As New List(Of Object) For Each c In ph.Contacts items.Add(New With {.Type = "Contact", .Id = c.ContactId, .Title = c.Title}) Next For Each c In ph.Persons items.Add(New With {.Type = "Person", .Id = c.PersonId, .Title = c.Title}) Next For Each c In ph.Jobs items.Add(New With {.Type = "Job", .Id = c.JobId, .Title = c.Title}) Next Is it possible to merge them all into one query or method line, I don't really care if this will be done with something other than linq, I am just looking for a more efficient way as I have a long list coming ahead, and the aggregating list will be strongly-typed using Dim list = blah blah

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• Sync Framework,LINQ, and my DAL

  - by Refracted Paladin

  I am creating a WPF app that needs to allow users to work in a temporary disconnected state and I plan to use a Local Database Cache. My question's are about my data access layer. Do you typically create the whole DAL to point at the Cache or both and create a switching mechanism? Is Entity's a good way to go for my DAL against the Cache? I am used to L2S but my understanding is that I can't use that against SQLCE, correct? Thanks! PS: Any good resources out there for using Sync, Linq, and WPF ALL TOGETHER? Tutorials, videos, etc?

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• Convert XML attributes to a Dictionary in Linq to XML

  - by NateD

  I've got a program that needs to convert two attributes of a particular tag to the key and value of an Dictionary<int,string>. The XML looks like this: (fragment) <startingPoint coordinates="1,1" player="1" /> and so far my LINQ looks something like this: XNamespace ns = "http://the_namespace"; var startingpoints = from sp in xml.Elements(ns+"startingPoint") from el in sp.Attributes() select el.Value; Which gets me a nice IEnumerable full of things like "1,1" and "1", but there should be a way to adapt something like this answer to do attributes instead of elements. Little help please? Thank you!

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• What's the convention for extending Linq datacontext with set based helper operations specific to on

  - by Luke Rohde

  Hi All I might be vaguing out here but I'm looking for a nice place to put set based helper operations in linq so I can do things like; db.Selections.ClearTemporary() which does something like db.DeleteAllOnSubmit(db.Selections.Where(s => s.Temporary)) Since I can figure out how to extend Table<Selection> the best I can do is create a static method in partial class of Selection (similar to Ruby) but I have to pass in the datacontext like; Selection.ClearTemporary(MyDataContext) This kind of sucks because I have two conventions for doing set based operations and I have to pass the data context to the static class. I've seen other people recommending piling helper methods into a partial of the datacontext like; myDataContext.ClearTemporarySelections(); But I feel this makes the dc a dumping ground for in-cohesive operations. Surely I'm missing something. I hope so. What's the convention? TIA

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• Using LINQ to SQL with multiple databases

  - by Stuart Ferguson

  I am working on a new project and hoping to use LINQ to SQL for the data access but have come across the following issue. I need to have my application access 3 databases with similar but not the same table structure, for example Database1 and Database 2 has a table called tblCustomer with 2 columns CustomerKey and CustomerName Database2 has a table called tblCustomer with 3 columns CustomerKey, CustomerName and CustomerPostCode I am looking for a solution that will allow me a query all three databases without the need for 3 GetCustomerList functions as Database1 and Database2 could use the same function as are the same structure, with an override function for database 3 to bring back the additional field. Is there a way i can declare a base datacontext class to handle Database 1 and 2 with an inherited version for Database 3. Thanks In Advance Stuart Ferguson

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• How to get index using LINQ?

  - by codymanix

  Given a datasource like that: var c = new Car[] { new Car{ Color="Blue", Price=28000}, new Car{ Color="Red", Price=54000}, new Car{ Color="Pink", Price=9999}, // .. }; How can I find the index of the first car satisfying a certain condition with LINQ? EDIT: I could think of something like this but it looks horrible: int firstItem = someItems.Select((item, index) => new { ItemName = item.Color, Position = index }).Where(i => i.ItemName == "purple") .First() .Position; Will it be the best to solve this with a plain old loop?

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• LINQ-To-SQL and Many-To-Many Relationship Deletions

  - by Jake

  I have a many-to-many relationship between two tables, let's say Friends and Foods. If a friend likes a food I stick a row into the FriendsFoods table, like this: ID Friend Food 1 'Tom' 'Pizza' FriendsFoods has a Primary Key 'ID', and two non-null foreign keys 'Friend' and 'Food' to the 'Friends' and 'Foods' tables, respectively. Now suppose I have a Friend tom .NET object corresponding to 'Tom', and Tom no longer likes pizza (what is wrong with him?) FriendsFoods ff = tom.FriendsFoods.Where(x => x.Food.Name == 'Pizza').Single(); tom.FriendsFoods.Remove(ff); pizza.FriendsFoods.Remove(ff); If I try to SubmitChanges() on the DataContext, I get an exception because it attempts to insert a null into the Friend and Food columns in the FriendsFoods table. I'm sure I can put together some kind of convoluted logic to track changes to the FriendsFoods table, intercept SubmitChanges() calls, etc to try and get this to work the way I want, but is there a nice, clean way to remove a Many-To-Many relationship with LINQ-To-SQL?

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• Using Linq methods causes missing references to DependencyObject in WindowsBase

  - by Jason Coyne

  I have some c# source that I want to compile using CodeDom within my application (for a plugin) Everything works fine, except if I use a Linq extension function on some of my collections var dict = new Dictionary<KeyType, ValueType>(); .... dict.Any(KV=>KV.Key == "Some Key); When I try to compile source that has this code, it CodeDom complains that I am missing a reference to DependencyObject in WindowsBase. I do not understand why this is happening. Neither the Dictionary class, or the Any extension method reference that class, which apparently is part of Windows.Forms I would normally just ignore the quirk, make the CodeDom add a reference and move on, but Apparently WindowsBase is special and is not always distributed and I don't want to cause issues for users that may not have it installed correctly.

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• LINQ aggregate / SUM grouping problem

  - by Chrissi

  I'm having trouble getting my head around converting a traditional SQL aggregate query into a LINQ one. The basic data dump works like so: Dim result = (From i As Models.InvoiceDetail In Data.InvoiceDetails.GetAll Join ih As Models.InvoiceHeader In Data.InvoiceHeaders.GetAll On i.InvoiceHeaderID Equals ih.ID Join p As Models.Product In Data.Products.GetAll On i.ProductID Equals p.ID Join pg As Models.ProductGroup In Data.ProductGroups.GetAll On p.ProductGroupID Equals pg.ID Join gl As Models.GLAccount In Data.GLAccounts.GetAll On pg.GLAccountSellID Equals gl.ID Where (gl.ID = GLID) Select ih.Period,i.ExtendedValue) What I need to really be getting out is ih.Period (a value from 1 to 12) and a corresponding aggregate value for i.ExtendedValue. When I try to Group ih I get errors about i being out of scope/context, and I'm not sure how else to go about it.

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• Mysql and Subsonic 3 with LINQ: Cannot insert rows

  - by Gustavo

  I'm using Susbsonic 3 with the LINQ templates. I've already added a column called 'ID' to my Articles table. When I try to insert a row using the following code var db = new LDB(); int newID = db.Insert.Into<ArticlesTable> ( x => x.Description ).Values( "TestDescription" ).Execute(); I get the following error message Can't decide which property to consider the Key - you can create one called 'ID' or mark one with SubSonicPrimaryKey attribute Any clue on what I'm doing wrong?

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• Linq Query Help Needed

  - by Randy Minder

  Say I have the following LINQ queries: var source = from workflow in sourceWorkflowList select new { SubID = workflow.SubID, ReadTime = workflow.ReadTime, ProcessID = workflow.ProcessID, LineID = workflow.LineID }; var target = from workflow in targetWorkflowList select new { SubID = workflow.SubID, ReadTime = workflow.ReadTime, ProcessID = workflow.ProcessID, LineID = workflow.LineID }; var difference = source.Except(target); sourceWorkflowList and targetWorkflowList have the exact same column definitions. But they both contain more columns of data than what is shown in the queries above. Those are just the columns needed for this particular issue. difference contains all rows in sourceWorkflowList that are not contained in targetWorkflowList Now what I would like to do is to remove all rows from sourceWorkflowList that do not exist in difference. Could someone show me a query that would do this? Thanks very much - Randy

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• LINQ to SQL join when there aren't results

  - by Boarder2

  Given the following database structure I'm trying to write a LINQ query that will return images grouped by tags it's associated with. So far I've got this: var images = from img in db.Images join imgTags in db.ImageTags on img.idImage equals imgTags.idImage join t in db.Tags on imgTags.idTag equals t.idTag where img.OCRData.Contains(searchText.Text) group img by new { t.TagName } into aGroup select new { GroupName = aGroup.Key.TagName, Items = from x in aGroup select new ImageFragment() { ImageID = x.idImage, ScanDate = x.ScanTime } }; Which works great. However, I also want to return Images that do not have any tags associated with them in a group of "(Untagged)" or something. I can't wrap my head around how I would do this without inserting a default tag for every image and that seems like generally not a very good solution.

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• how to read value of an xml node (single) using linq to xml

  - by Wondering

  Hi All, I have a xml structure similar to below one: <test> <test1>test1 value</test1> </test> Now I am reading the value of node using below LINQ to xml code. var test = from t in doc.Descendants("test") select t.Element("test1").Value; Console.WriteLine("print single node value"); Console.WriteLine(test); above code works fine, but here I have one single node, but to retrive value I am using foreach loop, which I dont think is good..any better way of doing the same thing without a foreach loop Thanks.

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• Getting multiple data items in an element with linq to xml

  - by Maestro1024

  Getting multiple data items in an element with linq to xml I have an xml file like this <TopLevel> <Inside> Jibba </Inside> <Inside> Jabba </Inside> </TopLevel> I was given said xml and and want to get all the elements. Here is the code I have. var q = from c in loaded.Descendants("TopLevel") select (XElement)c.Element("Inside"); I tried c.Elements but that did not work. What do I need to do to get all of the internal elements? This code just gets the first "Inside" tag.

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• Default Object being modified because of LINQ Query

  - by msarchet

  I'm doing the following code to filter a list of objects before it gets sent off to be printed. Dim printList As New List(Of dispillPatient) For Each pat As dispillPatient In patList If (From meds In pat.Medication Select meds Where meds.Print = True).Count > 0 Then Dim patAdd As New dispillPatient patAdd = pat patAdd.Medication = DirectCast((From meds In pat.Medication Select meds Where meds.Print = True).ToList, List(Of dispillMedication)) printList.Add(patAdd) End If Next What is happening is patList, which is my initial list, for every dispillPatient inside of it, that specific patients Medication object (which is another list), is being shorten to the list that is returned to the patAdd object. I think this has something to do with both the way that .NET makes the copy of my pat object when I do patAdd = pat and the LINQ query that I'm using. Has anyone had a similar issue before and\or what can I do to keep my initial list from getting truncated. Thanks

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• Linq to SQL Error with Many-to-Many table

  - by Matt Connolly

  I am getting the following error with linq-to-sql when I try to access a many-to-many collection: Members 'Int32 XXX' and 'Int32 YYY' both marked as IsPrimaryKey and IsDbGenerated. The statement is true, in that both of those columns are primary key integers with identity insert. The table I am trying to access has a foreign key to both YYY and ZZZ, and then ZZZ has a foreign key to XXX. There doesn't appear to be anything wrong with my data structure. I tried setting "Child Property" to false on the ZZZ-YYY relationship, but it didn't change anything.

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• what possible workarounds are there for "only parameterless constructors are support in Linq to Enti

  - by Ralph Shillington

  In my query I need to return instances of a class that doesn't have a default constructor (specifically this is in a custom Membership provider, and MembershipUser is the culprit) var users = from l in context.Logins select new MembershipUser( Name, l.Username, // username l.Id, // provider key l.MailTo, l.PasswordQuestion, l.Notes.FirstOrDefault().NoteText, l.IsApproved, l.IsLockedOut, l.CreatedOn, l.LastLoginOn.HasValue ? l.LastLoginOn.Value : DateTime.MinValue, l.LastActivityOn.HasValue ? l.LastActivityOn.Value : DateTime.MinValue, DateTime.MinValue, l.LastLockedOutOn.HasValue ? l.LastLockedOutOn.Value : DateTime.MinValue ); is syntacitally correct, but results in a runtime error as Only parameterless constructors and initializers are supported in LINQ to Entities.

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• Can you update/add records in SQL using a datagridview and LINQ to SQL

  - by Jordan S

  Is it possible to bind a DataGridView to a LINQ to SQL class so that when I make changes to the records in the datagridview it automatically updates the SQL database? I have tried binding the data like this but if I make changes to the data in the datagrid view they do not actually affect the data in the database... BOMClassesDataContext DB = new BOMClassesDataContext(); var mfrs = from m in DB.Manufacturers select m; BindingSource bs = new BindingSource(); bs.DataSource = mfrs; dataGridView1.DataSource = bs;

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• Linq Where Clauses - Better to stack or combine?

  - by burnt_hand

  When writing a method chain for LINQ, I can do the Where statements one of two ways: var blackOldCats = cats.Where(cat => cat.Age > 7 && cat.Colour == "noir" ) Or var blackOldCats = cats.Where(cat => cat.Age > 7).Where(cat.Colour == "noir" ) Are there any benefits of one over the other? Don't worry too much about the datatypes in this example, but if there are issues with datatypes, then that would be good to know too.

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• Insert record in Linq to Sql

  - by Anders Svensson

  Is this the easiest way to insert a record with Linq to Sql when there's a many-to-many relationship, or is there a better/cleaner way? I wasn't sure why things weren't working at first, but when I added a second SubmitChanges() it worked. Why was this necessary? Would be grateful if someone could clarify this a bit! private void InsertNew() { UserPageDBDataContext context = new UserPageDBDataContext(); User user = new User(); ManyToMany.Model.Page page = new ManyToMany.Model.Page(); user.Name = "Madde Andersson"; page.Url = "anderscom/references"; context.Users.InsertOnSubmit(user); context.Pages.InsertOnSubmit(page); context.SubmitChanges(); UserPage userPage = new UserPage(); userPage.UserID = user.UserID; userPage.PageID = page.PageID; user.UserPages.Add(userPage); context.SubmitChanges(); }

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• Problem with Linq query and date format

  - by Alan T

  Hi All I have a C# console application written using Visual Studio 2008. My system culture is en-GB. I have a Linq query that looks like this: var myDate = "19-May-2010"; var cus = from x in _dataContext.testTable where x.CreateDate == Convert.ToDateTime(myDate) select x; The resulting SQL query generates and error because it returns the dates as "19/05/2010" which it interprets as an incorrect date. For some reason even though my system culture is set to en-GB it looks like it's trying to intrepret it as a en-US date. Any ideas how I get around this? Thanks. Alan T

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• LINQ to remove duplicated property

  - by Shawn Mclean

  I have a LINQ statement like this: var media = (from p in postService.GetMedia(postId) select new { PostId = postId, SynthId = p.SynthId }); There are many(possibly thousands) of records returned with the same SynthId. I want to select one one, any random one. So when I'm finished, media should contain records with distinct SynthId. SynthId can be null, I want all nulls to be in media (the distinct should not affect them). My DAL is EntityFramework, if that will help. How do I accomplish this in the most efficient way?

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• ASP.NET MVC TDD with LINQ and SQL database

  - by dean nolan

  I am trying to start a new MVC project with tests and I thought the best way to go would have 2 databases. 1 for testing against and 1 for when I run the app and use it (also test really as it's not production yet). For the test database I was thinking of putting create table scripts and fill data scripts within the test setup method and then deleting all this in the tear down method. I am going to be using Linq to SQL though and I don't think that will allow me to do this? Will I have to just go the ADO route if I want to do it this way? Or should I just use a mock object and store data as an array or something?. Any tips on best practices? How did Jeff go about doing this for StackOveflow?

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• Make CSV from list of string in LINQ

  - by CmdrTallen

  Hi I would like to take a list collection and generate a single csv line. So take this; List<string> MakeStrings() { List<string> results = new List<string>(); results.add("Bob"); results.add("Nancy"); results.add("Joe"); results.add("Jack"); } string ContactStringsTogether(List<string> parts) { StringBuilder sb = new StringBuilder(); foreach (string part in parts) { if (sb.Length > 0) sb.Append(", "); sb.Append(part); } return sb.ToString(); } This returns "Bob,Nancy,Joe,Jack" Looking for help on the LINQ to do this in a single statement. Thanks!

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• Linq to sql add/update in different methods with different datacontexts

  - by Kurresmack

  I have to methods, Add() and Update() which both create a datacontext and returns the object created/updated. In my unit test I call first Add(), do some stuff and then call Update(). The problem is that Update() fails with the exception: System.Data.Linq.DuplicateKeyException: Cannot add an entity with a key that is already in use.. I understand the issue but want to know what to do about it? I've read a bit about how to handle multiple datacontext objects and from what I've heard this way is OK. I understand that the entity is still attached to the datacontext in Add() but I need to find out how to solve this? Thanks in advance

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