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• stepping into a linq query

  - by MyNameIsJob

  Is it possible to step into a linq query? I have a linq to entity framework 4 query in it's simplest form: List = List.Where(f => f.Value.ToString().ToLowerInvariant().Contains(filter.ToLowerInvariant())); It's a query against an Entity Framework DbContext and I'm having trouble seeing why it works for something like: List searching for 001 yields no results against the following list Test001 Test002 Test003 Test004 However any other search yields results (Such as t00 or Test) I was hoping to figure out a way to see the resulting sql but it appears that I need Intellitrace, which I don't currently have or possibly stepping through the query itself and see each iteration build itself.

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• Cannot convert lambda expression to type 'string' because it is not a delegate type

  - by RememberME

  I have the following code written by another developer on 2 pages of my site. This used to work just fine, but now is giving the error "Cannot convert lambda expression to type 'string' because it is not a delegate type" on the Delete line with Ajax.ThemeRollerActionLink. I don't go into this section of the site often, and we recently upgraded from MVC 1.0 to 2.0. I'm guessing that's probably when it stopped working. I've looked up this error and the recommended fix seems to be add using System.Linq However, the page already has <%@ Import Namespace="System.Linq" %> <% Html.Grid(Model).Columns(col => { col.For(c => "<a href='" + Url.Action("Edit", new { userName = c }) + "' class=\"fg-button fg-button-icon-solo ui-state-default ui-corner-all\"><span class=\"ui-icon ui-icon-pencil\"></span></a>").Named("Edit").DoNotEncode(); col.For(c => Ajax.ThemeRollerActionLink("fg-button fg-button-icon-solo ui-state-default ui-corner-all", "ui-icon ui-icon-close", "Delete", new { userName = c }, new AjaxOptions { Confirm = "Delete User?", HttpMethod = "Delete", InsertionMode = InsertionMode.Replace, UpdateTargetId = "gridcontainer", OnSuccess = "successDeleteAssignment", OnFailure = "failureDeleteAssignment" })).Named("Delete").DoNotEncode(); col.For(c => c).Named("User"); }).Attributes(id => "userlist").Render(); %>

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• I need to convert the result of a stored procedure in a dbml file to IQueryable to view a list in an

  - by RJ

  I have a MVC project that has a Linq to SQL dbml class. It is a table called Clients that houses client information. I can easily get the information to display in a View using the code I followed in Nerd Dinner but I have added a stored procedure to the dbml and it's result set is of IQueryable, not IQueryable. I need to convert IQueryable to IQueryable so I can display it in the same View. The reason for the sproc is so I can pass a search string tothe sproc and return the same information as a full list but filtered on the search. I know I can use Linq to filter the whole list but I don't want the whole list so I am using the sproc. Here is the code in my ClientRepository with a comment where I need to convert. What code goes in the commented spot. public IQueryable<Client> SelectClientsBySearch(String search) { IQueryable<SelectClientsBySearchResult> spClientList = (from p in db.SelectClientsBySearch(search) select p).AsQueryable(); //what is the code to convert IQueryable<SelectClientsBySearchResult> to IQueryable<Client> return clientList; }

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• How do I do a table join on two fields in my second table?

  - by Cannonade

  I have two tables: Messages - Amongst other things, has a to_id and a from_id field. People - Has a corresponding person_id I am trying to figure out how to do the following in a single linq query: Give me all messages that have been sent to and from person x (idself). I had a couple of cracks at this. Not quite right MsgPeople = (from p in db.people join m in db.messages on p.person_id equals m.from_id where (m.from_id == idself || m.to_id == idself) orderby p.name descending select p).Distinct(); This almost works, except I think it misses one case: "people who have never received a message, just sent one to me" How this works in my head So what I really need is something like: join m in db.messages on (p.people_id equals m.from_id or p.people_id equals m.to_id) Gets me a subset of the people I am after It seems you can't do that. I have tried a few other options, like doing two joins: MsgPeople = (from p in db.people join m in AllMessages on p.person_id equals m.from_id join m2 in AllMessages on p.person_id equals m2.to_id where (m2.from_id == idself || m.to_id == idself) orderby p.name descending select p).Distinct(); but this gives me a subset of the results I need, I guess something to do with the order the joins are resolved. My understanding of LINQ (and perhaps even database theory) is embarrassingly superficial and I look forward to having some light shed on my problem.

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• LINQ to Twitter Queries with LINQPad

  - by Joe Mayo

  LINQPad is a popular utility for .NET developers who use LINQ a lot.  In addition to standard SQL queries, LINQPad also supports other types of LINQ providers, including LINQ to Twitter.  The following sections explain how to set up LINQPad for making queries with LINQ to Twitter. LINQPad comes in a couple versions and this example uses LINQPad4, which runs on the .NET Framework 4.0. 1. The first thing you'll need to do is set up a reference to the LinqToTwitter.dll. From the Query menu, select query properties. Click the Browse button and find the LinqToTwitter.dll binary. You should see something similar to the Query Properties window below. 2. While you have the query properties window open, add the namespace for the LINQ to Twitter types.  Click the Additional Namespace Imports tab and type in LinqToTwitter. The results are shown below: 3. The default query type, when you first start LINQPad, is C# Expression, but you'll need to change this to support multiple statements.  Change the Language dropdown, on the Main window, to C# Statements. 4. To query LINQ to Twitter, instantiate a TwitterContext, by typing the following into the LINQPad Query window: var ctx = new TwitterContext(); Note: If you're getting syntax errors, go back and make sure you did steps #2 and #3 properly. 5. Next, add a query, but don't materialize it, like this: var tweets = from tweet in ctx.Status where tweet.Type == StatusType.Public select new { tweet.Text, tweet.Geo, tweet.User }; 6. Next, you want the output to be displayed in the LINQPad grid, so do a Dump, like this: tweets.Dump(); The following image shows the final results:   That was an unauthenticated query, but you can also perform authenticated queries with LINQ to Twitter's support of OAuth.  Here's an example that uses the PinAuthorizer (type this into the LINQPad Query window): var auth = new PinAuthorizer { Credentials = new InMemoryCredentials { ConsumerKey = "", ConsumerSecret = "" }, UseCompression = true, GoToTwitterAuthorization = pageLink => Process.Start(pageLink), GetPin = () => { // this executes after user authorizes, which begins with the call to auth.Authorize() below. Console.WriteLine("\nAfter you authorize this application, Twitter will give you a 7-digit PIN Number.\n"); Console.Write("Enter the PIN number here: "); return Console.ReadLine(); } }; // start the authorization process (launches Twitter authorization page). auth.Authorize(); var ctx = new TwitterContext(auth, "https://api.twitter.com/1/", "https://search.twitter.com/"); var tweets = from tweet in ctx.Status where tweet.Type == StatusType.Public select new { tweet.Text, tweet.Geo, tweet.User }; tweets.Dump(); This code is very similar to what you'll find in the LINQ to Twitter downloadable source code solution, in the LinqToTwitterDemo project.  For obvious reasons, I changed the value assigned to ConsumerKey and ConsumerSecret, which you'll have to obtain by visiting http://dev.twitter.com and registering your application. One tip, you'll probably want to make this easier on yourself by creating your own DLL that encapsulates all of the OAuth logic and then call a method or property on you custom class that returns a fully functioning TwitterContext.  This will help avoid adding all this code every time you want to make a query. Now, you know how to set up LINQPad for LINQ to Twitter, perform unauthenticated queries, and perform queries with OAuth. Joe

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• Linq - reuse expression on child property

  - by user175528

  Not sure if what I am trying is possible or not, but I'd like to reuse a linq expression on an objects parent property. With the given classes: class Parent { int Id { get; set; } IList<Child> Children { get; set; } string Name { get; set; } } class Child{ int Id { get; set; } Parent Dad { get; set; } string Name { get; set; } } If i then have a helper Expression<Func<Parent,bool> ParentQuery() { Expression<Func<Parent,bool> q = p => p.Name=="foo"; } I then want to use this when querying data out for a child, along the lines of: using(var context=new Entities.Context) { var data=context.Child.Where(c => c.Name=="bar" && c.Dad.Where(ParentQuery)); } I know I can do that on child collections: using(var context=new Entities.Context) { var data=context.Parent.Where(p => p.Name=="foo" && p.Childen.Where(childQuery)); } but cant see any way to do this on a property that isnt a collection. This is just a simplified example, actually the ParentQuery will be more complex and I want to avoid having this repeated in multiple places as rather than just having 2 layers I'll have closer to 5 or 6, but all of them will need to reference the parent query to ensure security.

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• Linq to SQL Intersect help needed

  - by mohang

  Hi, I have tried various suggestions given in SO. I still did not get the answers needed. Kindly help me. I appreciate your help. I have two sets. I need help to get the linq to sql intersection done. I have two sets. IQueryable<BusinessEntity> firstSet = from ent in all entities where ... // Code to get the first set. IQueryable<BusinessEntity> secondSet = from ent in all entities where... // Code to get the second set. Now I want the intersection, that is common elements of these sets. I have tried various ways including the following and I did not get the result I wanted. Please help me to get the right result. var commonEntities = (from ent1 in firstSet from ent2 in secondSet where ent1.BusinessEntityId == ent2.BusinessEntityId select ent1);

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• Finally! Entity Framework working in fully disconnected N-tier web app

  - by oazabir

  Entity Framework was supposed to solve the problem of Linq to SQL, which requires endless hacks to make it work in n-tier world. Not only did Entity Framework solve none of the L2S problems, but also it made it even more difficult to use and hack it for n-tier scenarios. It’s somehow half way between a fully disconnected ORM and a fully connected ORM like Linq to SQL. Some useful features of Linq to SQL are gone – like automatic deferred loading. If you try to do simple select with join, insert, update, delete in a disconnected architecture, you will realize not only you need to make fundamental changes from the top layer to the very bottom layer, but also endless hacks in basic CRUD operations. I will show you in this article how I have  added custom CRUD functions on top of EF’s ObjectContext to make it finally work well in a fully disconnected N-tier web application (my open source Web 2.0 AJAX portal – Dropthings) and how I have produced a 100% unit testable fully n-tier compliant data access layerfollowing the repository pattern. http://www.codeproject.com/KB/linq/ef.aspx In .NET 4.0, most of the problems are solved, but not all. So, you should read this article even if you are coding in .NET 4.0. Moreover, there’s enough insight here to help you troubleshoot EF related problems. You might think “Why bother using EF when Linq to SQL is doing good enough for me.” Linq to SQL is not going to get any innovation from Microsoft anymore. Entity Framework is the future of persistence layer in .NET framework. All the innovations are happening in EF world only, which is frustrating. There’s a big jump on EF 4.0. So, you should plan to migrate your L2S projects to EF soon.

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• Linq query with aggregate function OrderBy

  - by Billy Logan

  Hello everyone, I have the following LinqToEntities query, but am unsure of where or how to add the orderby clause: var results = from d in db.TBLDESIGNER join s in db.TBLDESIGN on d.ID equals s.TBLDESIGNER.ID where s.COMPLETED && d.ACTIVE let value = new { s, d} let key = new { d.ID, d.FIRST_NAME, d.LAST_NAME } group value by key into g orderby g.Key.FIRST_NAME ascending, g.Key.LAST_NAME ascending select new { ID = g.Key.ID, FirstName = g.Key.FIRST_NAME, LastName = g.Key.LAST_NAME, Count = g.Count() }; This should be sorted by First_Name ascending and then Last_Name ascending. I have tried adding ordering but It has had no effect on the result set. Could someone please provide an example of where the orderby would go assuming the query above. Thanks, Billy

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• Linq : problem with primary key

  - by Nickson

  I get the following error message The table/view 'TABLE1' does not have a primary key defined and no valid primary key could be inferred. This table/view has been excluded. To use the entity you will need to review your schema, add the correct keys and uncomment it when I try to add a view to an Entity Data Model. For testing, I have created a very simple view and I still get the error. below is the view definition SELECT DISTINCT TOP (100) PERCENT MIN(id) AS Expr4, MIN(EmpNo) AS Expr1, MIN(Name) AS Expr2, MIN(Category) AS Expr3 FROM dbo.MYView1 GROUP BY id does any one know of a simple work around. I have looked at this thread http://stackoverflow.com/questions/745341/can-ms-sql-views-have-primary-and-foriegn-keys but in my scenario, what is recommended is not applicable. If I could only have the view added to the Model.

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• Solving Combinatory Problems with LINQ /.NET4

  - by slf

  I saw this article pop-up in my MSDN RSS feed, and after reading through it, and the sourced article here I began to wonder about the solution. The rules are simple: Find a number consisting of 9 digits in which each of the digits from 1 to 9 appears only once. This number must also satisfy these divisibility requirements: The number should be divisible by 9. If the rightmost digit is removed, the remaining number should be divisible by 8. If the rightmost digit of the new number is removed, the remaining number should be divisible by 7. And so on, until there's only one digit (which will necessarily be divisible by 1). This is his proposed monster LINQ query: // C# and LINQ solution to the numeric problem presented in: // http://software.intel.com/en-us/blogs/2009/12/07/intel-parallel-studio-great-for-serial-code-too-episode-1/ int[] oneToNine = new int[] { 1, 2, 3, 4, 5, 6, 7, 8, 9 }; // the query var query = from i1 in oneToNine from i2 in oneToNine where i2 != i1 && (i1 * 10 + i2) % 2 == 0 from i3 in oneToNine where i3 != i2 && i3 != i1 && (i1 * 100 + i2 * 10 + i3) % 3 == 0 from i4 in oneToNine where i4 != i3 && i4 != i2 && i4 != i1 && (i1 * 1000 + i2 * 100 + i3 * 10 + i4) % 4 == 0 from i5 in oneToNine where i5 != i4 && i5 != i3 && i5 != i2 && i5 != i1 && (i1 * 10000 + i2 * 1000 + i3 * 100 + i4 * 10 + i5) % 5 == 0 from i6 in oneToNine where i6 != i5 && i6 != i4 && i6 != i3 && i6 != i2 && i6 != i1 && (i1 * 100000 + i2 * 10000 + i3 * 1000 + i4 * 100 + i5 * 10 + i6) % 6 == 0 from i7 in oneToNine where i7 != i6 && i7 != i5 && i7 != i4 && i7 != i3 && i7 != i2 && i7 != i1 && (i1 * 1000000 + i2 * 100000 + i3 * 10000 + i4 * 1000 + i5 * 100 + i6 * 10 + i7) % 7 == 0 from i8 in oneToNine where i8 != i7 && i8 != i6 && i8 != i5 && i8 != i4 && i8 != i3 && i8 != i2 && i8 != i1 && (i1 * 10000000 + i2 * 1000000 + i3 * 100000 + i4 * 10000 + i5 * 1000 + i6 * 100 + i7 * 10 + i8) % 8 == 0 from i9 in oneToNine where i9 != i8 && i9 != i7 && i9 != i6 && i9 != i5 && i9 != i4 && i9 != i3 && i9 != i2 && i9 != i1 let number = i1 * 100000000 + i2 * 10000000 + i3 * 1000000 + i4 * 100000 + i5 * 10000 + i6 * 1000 + i7 * 100 + i8 * 10 + i9 * 1 where number % 9 == 0 select number; // run it! foreach (int n in query) Console.WriteLine(n); Octavio states "Note that no attempt at all has been made to optimize the code", what I'd like to know is what if we DID attempt to optimize this code. Is this really the best this code can get? I'd like to know how we can do this best with .NET4, in particular doing as much in parallel as we possibly can. I'm not necessarily looking for an answer in pure LINQ, assume .NET4 in any form (managed c++, c#, etc all acceptable).

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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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• How to optimize this Linq query

  - by Luke101

  I am trying to optimize this query. It is not slow for now but I am expecting a spike to hit this query in the near future. Is there anything else i can do to make this query faster? var posts = from p in context.post where p.post_isdeleted == false && p.post_parentid == null select new { p.post_date, p.post_id, p.post_titleslug, p.post_title, p.post_descriptionrender, p.userinfo.user_username, p.userinfo.user_userid, p.userinfo.user_GravatarHash, p.userinfo.user_points, p.category.catid, p.category.name, p.post_answercount, p.post_hasbestanswer, p.post_hits, p.post_isanonymous, p.post_votecount, FavoriteCount = context.favorites.Where(x => x.post.post_id == p.post_id).Count(), tags = from tg in context.posttag where tg.posttag_postid == p.post_id select new { tg.tag.tag_id, tg.tag.tag_title } };

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• LINQ to Entites: How should I handle System.InvalidOperationException when checking for existance of

  - by chris

  I have a many-to-one relationship that users can edit via checkboxes. PK of Foo is ID, and fid contains the id from the checkbox. I'm checking to see if an element exists with: Foo ent; try { ent = ctx.Foo.First(f => f.ID == fid); } catch (System.InvalidOperationException ioe) { ent = new Foo(); } It seems to me that I should be able to do this without throwing an exception. What would be the best way to do this?

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• Manual Linq to SQL entity framework mapping

  - by kprobst

  I've been playing with the O/R designer in VS and I was wondering if someone could shed come light on this. I'm used to OR mappers that are largely manual (homegrown and e.g., NHibernate). I don't mind encoding the entity classes myself, since they don't change all that often to begin with, and I have this irrational fear of designers and auto generated code as it is. I have noticed that the generated entity classes contain a lot of boilerplate extensibility methods, e.g. On[Property]Changed() and so on where [Property] is a mapped member of the class. These are placed in the setters of the property accessors. I assume it's OK if I don't include these when I do my hand coding, correct? They would be nice if I needed some sort of interception pattern but that's certainly not the case. I guess I just need to know if any of those methods are required by the entity framework to keep track of changes to the mapping types in order for things to work when updating the database. Thanks!

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• LINQ to Entites: Doing a count over one-to-many relationships

  - by chris

  I have a couple of tables where there are one to many relationships. Let's say I have a Country table, a State table with a FK to Country, and a City table with a FK to State. I'd like to be able to create a count of all Cities for a given country, and also a count of cities based on a filter - something like: foreach( var country in Model.Country ) { total = country.State.All().City.All().Count() ; filtered = country.State.All().City.Any(c=>c.field == value).Count(); } Obviously, this doesn't work - is there any way to do this?

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• BindingSource And ComboBox: Combobox Binded on another Source

  - by Garcia Julien

  Hi, I would like to make Something in my form. I have a Binding source binded on Linq to Sql Class. The class Workorder contains one field Site. I would like to display The combobox with all the site, but selected on the site form my workorder. I'm clear? Julien

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• LINQDataSource - Query Multiple Tables?

  - by davemackey

  I have a database and I've created a DBML Linq-to-SQL file to represent this database. I've created a new aspx page and dropped a linqdatasource and a formview control onto it. When I configure the linqdatasource it gives me the choice only to select * from one table...but I want to pull from multiple tables. e.g. I have tables like simple_person, simple_address, simple_phone, and I want to pull from all of them. How can I accomplish this?

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• Group by and order by

  - by Simon Thompson

  using LINQ to NHibernate does anybody know how to use group by and order by in the same expression. I am having to execute the group by into a list and then order this, seem that I am missing soemthing here ??? Example:- Private function LoadStats(...) ... Dim StatRepos As DataAccess.StatsExtraction_vwRepository = New DataAccess.StatsExtraction_vwRepository return (From x In StatRepos.GetAnswers(Question, Questionnaire) _ Group x By xData = x.Data Into Count() _ Select New ChartData With {.TheData = xData, .TheValue = xData.Count} ).ToList.OrderBy(Function(x) x.TheData) End Sub

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• Select some records ...

  - by Kris-I

  I have an IList<MyList>. I'd like with LINQ keep the same list (same number of record) but I'd like reduce or/and rename some record. At the end I'd like to have IList<MyNewList>.

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• Friendly way to parse XDocument

  - by Oli

  I have a class that various different XML schemes are created from. I create the various dynamic XDocuments via one (Very long) statement using conditional operators for optional elements and attributes. I now need to convert the XDocuments back to the class but as they are coming from different schemes many elements and sub elements may be optional. The only way I know of doing this is to use a lot of if statements. This approach doesn't seem very LINQ and uses a great deal more code than when I create the XDocument so I wondered if there is a better way to do this? An example would be to get <?xml version="1.0"?> <root xmlns="somenamespace"> <object attribute1="This is Optional" attribute2="This is required"> <element1>Required</element1> <element1>Optional</element1> <List1> Optional List Of Elements </List1> <List2> Required List Of Elements </List2> </object> </root> Into public class Object() { public string Attribute1; public string Attribute2; public string Element1; public string Element2; public List<ListItem1> List1; public List<ListItem2> List2; } In a more LINQ friendly way than this: public bool ParseXDocument(string xml) { XNamespace xn = "somenamespace"; XDocument document = XDocument.Parse(xml); XElement elementRoot = description.Element(xn + "root"); if (elementRoot != null) { //Get Object Element XElement elementObject = elementRoot.Element(xn + "object"); if(elementObject != null) { if(elementObject.Attribute(xn + "attribute1") != null) { Attribute1 = elementObject.Attribute(xn + "attribute1"); } if(elementObject.Attribute(xn + "attribute2") != null) { Attribute2 = elementObject.Attribute(xn + "attribute2"); } else { //This is a required Attribute so return false return false; } //If, If/Elses get deeper and deeper for the next elements and lists etc.... } else { //Object is a required element so return false return false; } } else { //Root is a required element so return false return false; } return true; } Update: Just to clarify the ParseXDocument method is inside the "Object" class. Every time an xml document is received the Object class instance has some or all of it's values updated.

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• Manual (Dynamic) LINQ subquery using IN clause

  - by immortalali-msn-com

  Hi Everyone, I want to query the DB through LINQ writing manual SQL, my linq method is: var q = db.TableView.Where(sqlAfterWhere); returnValue = q.Count(); this method queries well if the value passed to variable "sqlAfterWhere" is: (this variable is String type) it.Name = 'xyz' but what if i want to use IN clause, using a sub query. (i need to use 'it' before every column name in the above query to work), i cant use 'it' before the sub query columns as its a separate query, so what should i do, if i dont use any thing, and use column names directly it gives error saying " could not be resolved" where is my column names with out 'it' at the begining. So the query not working is: (this is a string passed to the variable above): it.Name IN (SELECT Name FROM TableName WHERE Address LIKE '%SomeAddress%') the errors come out as: Name could not be resolved Address could not be resolved The exact error is: "'Name' could not be resolved in the current scope or context. Make sure that all referenced variables are in scope, that required schemas are loaded, and that namespaces are referenced correctly., near simple identifier, line 6, column 25." Same error for "Address as well if i use 'it.' before these columns it gives error as: "The element type 'Edm.Int32' and the CollectionType 'Transient.collection[Transient.rowtype(GroupID,Edm.Int32(Nullable=True,DefaultValue=))]' are not compatible. The IN expression only supports entity, primitive, and reference types. , near WHERE predicate, line 6, column 14." Thanks for the help

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• LINQ - IEnumerable.Join on Anonymous Result Set in VB.NET

  - by user337501

  I've long since built a way around this, but it still keeps bugging me... it doesnt help that my grasp of dynamic LINQ queries is still shakey. For the example: Parent has fields (ParentKey, ParentField) Child has fields (ChildKey, ParentKey, ChildField) Pet has fields (PetKey, ChildKey, PetField) Child has a foreign key reference to Parent on Child.ParentKey = Parent.ParentKey Pet has a foreign key reference to Child on Pet.Childkey = Child.ChildKey Simple enough eh? Lets say I have LINQ like this... Dim Q = FROM p in DataContext.Parent _ Join c In DataContext.Child On c.ParentKey = p.ParentKey Consider this a "base query" on which I will perform other filtering actions. Now I want to join the Pet table like this: Q = Q.Join(DataContext.Pet, _ Function(a) a.c.ChildKey, _ Function(p As Pet) p.ChildKey, _ Function(a, p As Pet) p.ChildKey = a.c.ChildKey) The above Join call doesnt work. I sort of understand why it doesnt work, but hopefully it'll show you how I tried to accomplish this task. After all this was done I would have appended a Select to finish the job. Any ideas on a better way to do this? I tried it with the PredicateBuilder with little success. I might not know how to use it right but it felt like it wasnt gonna handle the joining.

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• LINQ To SQL ignore unique constraint exception and continue

  - by Martin

  I have a single table in a database called Users Users ------ ID (PK, Identity) Username (Unique Index) I have setup a unique index on the Username table to prevent duplicates. I am then enumerating through a collection and creating a new user in the database for each item. What I want to do is just insert a new user and ignore the exception if the unique key constraint is violated (as it's clearly a duplicate record in that case). This is to avoid having to craft where not exists kind of queries. First off, is this going to be any more efficient or should my insert code be checking for duplicates instead? I'm drawn more to the database having that logic as this prevents any other type of client from inserting duplicate data. My other issue is related to LINQ To SQL. I have the following code: public class TestRepo { DatabaseDataContext database = new DatabaseDataContext(); public void Add(string username) { database.Users.InsertOnSubmit(new User() { Username = username }); } public void Save() { database.SubmitChanges(); } } And then I iterate over a collection and insert new users, ignoring any exceptions: TestRepo repo = new TestRepo(); foreach (var name in new string[] { "Tim", "Bob", "John" }) { try { repo.Add(name); repo.Save(); } catch { } } The first time this is run, great I have three users in the table. If I remove the second one and run this code again, nothing is inserted. I expected the first insert to fail with the exception, the second to succeed (as I just removed that item from the DB) and the third to then fail. What seems to be happening is that once the SqlException is thrown (even though the loop continues to iterate) all of the next inserts fail - even when there isn't a row in the table that would cause a unique violation. Can anyone explain this? P.S. The only workaround I could find was to instantiate the repo each time before the insert, then it worked exactly as excepted - indicating that it's something to do with the LINQ To SQL DataContext. Thanks.

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• Linq-to-Sql IIS7 Login failed for user ‘DOMAIN\MACHINENAME$’

  - by cfdev9

  I am encountering unexpected behaviour using Linq-to-sql DataContext. When I run my application locally it works as expected however after deploying to a test server which runs IIS7, I get an error Login failed for user ‘DOMAIN\MACHINENAME$’ when attempting to open objects from the DataContext. This code explains the error, which breaks on the very last line with the error "System.Data.SqlClient.SqlException: Login failed for user". var connStr ="Data Source=server;Initial Catalog=Test;User Id=testuser;Password=password"; //Test 1 var conn1 = new System.Data.SqlClient.SqlConnection(connStr); var cmdString = "SELECT COUNT(*) FROM Table1"; var cmd = new System.Data.SqlClient.SqlCommand(cmdString, conn1); conn1.Open(); var count1 = cmd.ExecuteScalar(); conn1.Close(); //Test 2 var conn2 = new System.Data.SqlClient.SqlConnection(connStr); var context = new TestDataContext(conn2); var count2 = context.Table1s.Count(); The connection string is not even using integrated security, so why is Linq-to-sql trying to connect as a specific user? If I change the server name in the connection string I get a different error so its using atleast part of the connection string, but apparently ignoring the UserId and Password. Very confused.

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