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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 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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• 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 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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• Help with linq to sql compiled query

  - by stackoverflowuser

  Hi I am trying to use compiled query for one of my linq to sql queries. This query contains 5 to 6 joins. I was able to create the compiled query but the issue I am facing is my query needs to check if the key is within a collection of keys passed as input. But compiled queries do not allow passing of collection (since collection can have varying number of items hence not allowed). For instance input to the function is a collection of keys. Say: List<Guid> InputKeys List<SomeClass> output = null; var compiledQuery = CompiledQueries.Compile<DataContext, IQueryable<SomeClass>>( (context) => from a in context.GetTable<A>() where InputKeys.Contains(a.Key) select a); using(var dataContext = new DataContext()) { output = compiledQuery(dataContext).ToList(); } return output; Is there any work around or better way to do the above?

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• ADO.NET Entity Model and LINQ

  - by Richard

  Hi all I'm using an ADO.NET Entity Model which I'm trying to query using LINQ. The problem I'm having is that I can't specify the where clause as I'd like. For instance, consider the following query: AccountsDM db = new AccountsDM(ConfigurationManager.ConnectionStrings["PrimaryEF"].ConnectionString); var accounts = from a in db.Accounts select a; foreach (var account in accounts) { foreach (var ident in account.Identifiers) { if (ident.Identifier == identifier) { // ident.Identifier is what I'd like to be filtering in the WHERE clause below } } } Ideally, I'd like that to become: var accounts = from a in db.Accounts where a.Identifiers.Identifier == identifier select a; I'm guessing I've probably not set up my Entity Model correctly in VS2010. Any advice you can offer would be gratefully received. Thanks, Richard.

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• linq to sql datacontext for a web application

  - by rap-uvic

  Hello, I'm trying to use linq to sql for my project (very short deadline), and I'm kind of in a bind. I don't know the best way to have a data context handy per request thread. I want something like a singleton class from which all my repository classes can access the current data context. However, singleton class is static and is not thread-safe and therefore not suitable for web apps. I want something that would create a data context at the beginning of the request and dispose of it along with the request. Can anyone please share their solution to this problem? I've been searching for a solution and I've found a good post from Rick Strahl : http://www.west-wind.com/weblog/posts/246222.aspx but I don't completely understand his thread-safe or business object approach. If somebody has a simplified version of his thread-safe approach, i'd love to take a look.

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• Linq to sql translation to sql of custom method

  - by DJPB

  hi there is there a way to translate an expression to sql to use with linq to sql? for example I have a method that compares two values example: MyComparer.Compare(value1, value2, ">") return value1 > value2 MyComparer.Compare(value1, value2, "=") return value1 == value2 MyComparer.Compare(value1, value2, "<=") return value1 <= value2 and i would like a query like var list = from i in dataContext.items where MyComparer.Compare(i.value, someValue, "some operator") select ... this won't work because, obviously, MyComparer doesn't translate to sql maybe this is a twisted question, but how can i translate this method to sql or is this possible? tks

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• LINQ To SQL Wildcards

  - by mcass20

  How can I build in wildcards to my LINQ To SQL lambda expression? This is what I have currently: var query = from log in context.Logs select log; foreach (string filter in CustomReport.ExtColsToFilter) { string tempFilter = filter; query = query.Where(Log => Log.FormattedMessage.Contains(tempFilter)); } This works fine up until I try and pass wildcards in the filter string. I'm experimenting with SqlMethods.Like() but to no avail. The filters above look like this: "<key>NID</key><value>mcass</value>". I'd like to be able to pass filters like this: "<key>NID</key><value>%m%</value>"

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• Getting a set of elements using linq

  - by MarceloRamires

  I have the following piece of XML: <xml> <ObsCont xCampo="field1"> <xTexto>example1</xTexto> </ObsCont> <ObsCont xCampo="field2"> <xTexto>example2</xTexto> </ObsCont> <ObsCont xCampo="field3"> <xTexto>example3</xTexto> </ObsCont> </xml> How do I (using linq) get for example what is inside the xTexto tag that has as parent the ObsCont with the xCampo attribute "field2" ? (c#, vb.net, your choice)

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• Should methods containing LINQ expressions be tested / mocked?

  - by Phil.Wheeler

  Assuming I have a class with a method that takes a System.Linq.Expressions.Expression as a parameter, how much value is there in unit testing it? public void IEnumerable<T> Find(Expression expression) { return someCollection.Where(expression).ToList(); } Unit testing or mocking these sorts of methods has been a mind-frying experience for me and I'm now at the point where I have to wonder whether it's all just not worth it. How would I unit test this method using some arbitrary expression like List<Animal> = myAnimalRepository.Find(x => x.Species == "Cat");

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• Binding Linq To Entities query results to a datagridview

  - by Nickson

  I just started playing with Linq to entities in a windows forms application and am not understanding one behavior that looks so simple though. If i type code below, i get ReadOnly records in my dataGridView Dim x = From n in Table1 _ Select n.FirstName, n.LastName, N.Department DataGridView1.DataSource = x But if i type the following code, i get editable rows in my dataGridView Dim x = From n in Table1 _ Select n DataGridView1.DataSource = x So, basically if i specify the column names to select and databind to my DataGridView1, the rows are readonly but if i do not specify the column names and databind to the DataGridView, the rows are editable and i don't understand why.

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