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• Linq - How to query specific columns and return a lists

  - by Billy Logan

  Hello Everyone, I am trying to write a linq query that will only return certain columns from my entity object into a list object. Below is my code which produces an error(can't implicitly convert a generic list of anonymous types to a generic list of type TBLPROMOTION): List<TBLPROMOTION> promotionInfo = null; promotionInfo = (from p in matches orderby p.PROMOTION_NM descending select new { p.EFFECTIVE_DT, p.EXPIRE_DT, p.IS_ACTIVE, p.PROMOTION_DESC, p.PROMOTION_ID, p.PROMOTION_NM }).ToList(); What would be the best way to accomplish this. I do not want to do a "select p" in this case and return all the columns associated with the query. thanks in advance, Billy

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• In LINQ-SQL, wrap the DataContext is an using statement - pros cons

  - by hIpPy

  Can someone pitch in their opinion about pros/cons between wrapping the DataContext in an using statement or not in LINQ-SQL in terms of factors as performance, memory usage, ease of coding, right thing to do etc. Update: In one particular application, I experienced that, without wrapping the DataContext in using block, the amount of memory usage kept on increasing as the live objects were not released for GC. As in, in below example, if I hold the reference to List of q object and access entities of q, I create an object graph that is not released for GC. DataContext with using using (DBDataContext db = new DBDataContext()) { var q = from x in db.Tables where x.Id == someId select x; return q.toList(); } DataContext without using and kept alive DBDataContext db = new DBDataContext() var q = from x in db.Tables where x.Id == someId select x; return q.toList(); Thanks.

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• LINQ OrderBy: best search results at top of results list

  - by p.campbell

  Consider the need to search a list of Customer by both first and last names. The desire is to have the results list sorted by the Customer with the most matches in the search terms. FirstName LastName ---------- --------- Foo Laurie Bar Jackson Jackson Bro Laurie Foo Jackson Laurie string[] searchTerms = new string[] {"Jackson", "Laurie"}; //want to find those customers with first, last or BOTH names in the searchTerms var matchingCusts = Customers .Where(m => searchTerms.Contains(m.FirstName) || searchTerms.Contains(m.LastName)) .ToList(); /* Want to sort for those results with BOTH FirstName and LastName matching in the search terms. Those that match on both First and Last should be at the top of the results, the rest who match on one property should be below. */ return matchingCusts.OrderBy(m=>m); Desired Sort: Jackson Laurie (matches on both properties) Foo Laurie Bar Jackson Jackson Bro Laurie Foo How can I achieve this desired functionality with LINQ and OrderBy / OrderByDescending?

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• linq sort many 2 many question

  - by user169867

  My main entity is called [Contract]. Contract has a many 2 many relationship w/ [Service]. When I query for a list of Contracts I grab the 1st Service available like this: q.Select(c => new ContractSearchResult() { ContractID = c.ContractID, FirstService = c.Contract2Service.FirstOrDefault().Service.Name, ServiceCount = c.Contract2Service.Count, } ).ToList(); q is an IQueryable that has some filtering & paging already applied. (When I display this list I show the FirstService if there's only 1. If 1 I show "My1stService (3)" to show I'm seeing the 1st of 3 services) This works fine. My question is this: Is there any way to sort by FirstService? Or is this impossible? I haven't found a way of expressing this in linq. Any help would be appreciated.

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• Linq query - multiple where, with extension method

  - by Cj Anderson

  My code works for ORs as I've listed it below but I want to use AND instead of OR and it fails. I'm not quite sure what I'm doing wrong. Basically I have a Linq query that searches on multiple fields in an XML file. The search fields might not all have information. Each element runs the extension method, and tests the equality. Any advice would be appreciated. refinedresult = From x In theresult _ Where x.<thelastname>.Value.TestPhoneElement(LastName) Or _ x.<thefirstname>.Value.TestPhoneElement(FirstName) Or _ x.<id>.Value.TestPhoneElement(Id) Or _ x.<number>.Value.TestPhoneElement(Telephone) Or _ x.<location>.Value.TestPhoneElement(Location) Or _ x.<building>.Value.TestPhoneElement(building) Or _ x.<department>.Value.TestPhoneElement(Department) _ Select x Public Function TestPhoneElement(ByVal parent As String, ByVal value2compare As String) As Boolean 'find out if a value is null, if not then compare the passed value to see if it starts with Dim ret As Boolean = False If String.IsNullOrEmpty(parent) Then Return False End If If String.IsNullOrEmpty(value2compare) Then Return ret Else ret = parent.ToLower.StartsWith(value2compare.ToLower.Trim) End If Return ret End Function

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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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• LINQ To Entities - Items, ItemCategories & Tags

  - by Simon

  Hi There, I have an Entity Model that has Items, which can belong to one or more categories, and which can have one or more tags. I need to write a query that finds all tags for a given ItemCategory, preferably with a single call to the database, as this is going to get called fairly often. I currently have: Dim q = (From ic In mContext.ItemCategory _ Where ic.CategoryID = forCategoryID _ Select ic).SelectMany(Function(cat) cat.Items).SelectMany(Function(i) i.Tags) _ .OrderByDescending(Function(t) t.Items.Count).ToList This is nearly there, apart from it doesn't contain the items for each tag, so I'd have to iterate through, loading the item reference to find out how many items each tag is related to (for font sizing). Ideally, I want to return a List(Of TagCount), which is just a structure, containing Tag as string, and Count as integer. I've looked at Group and Join, but I'm not getting anywhere so any help would be greatly appreciated!

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• How to do a STAR search in LINQ

  - by aNui

  I'm not sure about clarity of the STAR word. I'm implementing a search method using linq-to-object in c#. And I want to do a search with * (star) operator like most of search apps or web can do. e.g. If I typed "p*", results should be everything starting with "p". And it should work for prefix star, suffix star or star in the middle. And it would be great if the search can do with "-" (minus/NOT) operator or "+" (plus/OR) operator or "AND" operator Thanks in advance.

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• Dynamic Linq Library Help

  - by Alon

  Hi, I have the following class: public class Item { public Dictionary<string, string> Data { get; set; } } and a list of it: List<Item> items; I need to filter and order this list dynamicly using SQL-Like strings. The catch is, that I need to order it by the Data dictionary. For example: Order By Data["lastname"] or Where Data["Name"].StartsWith("a"). I thought to use the dynamic linq library, but is there any way that my clients can write without the Data[]? For example: Name.StartsWith("abc") instead of Data["Name"].StartsWith("abc") ? Thank you.

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• How to perform a many-to-many Linq query with Include in the EF.

  - by despart

  Hi, I don't know how to perform this query using Linq and the EF. Imagine I have three tables A, B and C. A and B have a many-to-many relationship. B and C have a 1-to-many relationship. I want to obtain records from B including C but filtering from A's Id. I can get easily the records from B: var b = Context.A.Where(x => x.Id.Equals(aId)).SelectMany(x => x.B); but when I try to include C I don't know how to do it: //This doesn't work var b = Context.A.Where(x => x.Id.Equals(aId)).SelectMany(x => x.B.Include("C")); Also I've tried this with no luck (it is equivalent to the above): //Not working var b = (from a in Context.A.Where(x => x.Id.Equals(aId)) from b in a.B.Include("C") select b); Thanks for your help.

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• Using LINQ to find a common prefix?

  - by Roger Lipscombe

  I've got two sequences: IEnumerable<string> x = new[] { "a", "b", "c" }; IEnumerable<string> y = new[] { "a", "b", "d", "e" }; I'd like to find the common prefix of these two sequences (i.e. "a", "b"). Is there a succinct way to do this in LINQ? Bear in mind that these aren't really IEnumerable<string>; they're IEnumerable<PathComponent>, where I have an implementation of IEqualityComparer<PathComponent>.

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• how to convert Database Hierarchical Data to XML using ASP.net 3.5 and LINQ

  - by mahdiahmadirad

  hello guys! i have a table with hierarchical structure. like this: and table data shown here: this strategy gives me the ability to have unbounded categories and sub-categories. i use ASP.net 3.5 SP1 and LINQ and MSSQL Server2005. How to convert it to XML? I can Do it with Dataset Object and ".GetXML()" method. but how to implement it with LINQtoSQL or LINQtoXML??? or if there is another simpler way to perform that? what is your suggestion? the best way? I searched the web but found nothing for .net 3.5 featuers.

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• LINQ Expression<Func<T, bool>> equavalent of .Contains()

  - by BK

  Has anybody got an idea of how to create a .Contains(string) function using Linq Expressions, or even create a predicate to accomplish this public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> expr1, Expression<Func<T, bool>> expr2) { var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>()); return Expression.Lambda<Func<T, bool>> (Expression.OrElse(expr1.Body, invokedExpr), expr1.Parameters); } Something simular to this would be ideal?

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• LINQ expression precedence with Skip(), Take() and OrderBy()

  - by Robert Koritnik

  I'm using LINQ to Entities and display paged results. But I'm having issues with the combination of Skip(), Take() and OrderBy() calls. Everything works fine, except that OrderBy() is assigned too late. It's executed after result set has been cut down by Skip() and Take(). So each page of results has items in order. But ordering is done on a page handful of data instead of ordering of the whole set and then limiting those records with Skip() and Take(). How do I set precedence with these statements? My example (simplified) var query = ctx.EntitySet.Where(/* filter */).OrderBy(/* expression */); int total = query.Count(); var result = query.Skip(n).Take(x).ToList();

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• Converting SQL to LINQ to XML

  - by Morano88

  I'm writing the following code to convert SQL to LINQ and then to XML: SqlConnection thisConnection = new SqlConnection(@"Data Source=3BDALLAH-PC;Initial Catalog=XMLC;Integrated Security=True;Pooling=False;"); thisConnection.Open(); XElement eventsGive = new XElement("data", from c in ?????? select new XElement("event", new XAttribute("start", c.start), new XAttribute("end",c.eend), new XAttribute("title",c.title), new XAttribute("Color",c.Color), new XAttribute("link",c.link))); Console.WriteLine(eventsGive); The name of the table is "XMLC" and I want to refer to it. How can I do that? When I put its name directly VS gives an error. Also when I say thisConnection.XMLC it doesn't work.

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• Use delegate for Projection in Linq to SQL

  - by Redeemed1

  I have code something like this in an IRepository implementation in Linq to Sql: var newlist = from h in list where h.StringProp1 == "1" select new MyBusinessBO{ firstProp = h.StringProp1, secondProp = h.StringProp2 }; The projection into MyBusinessBO is not difificult but when the Business Object has many properties the projection code becomes very lengthy. Also, as the projection can occur in several places in the Repository we break the DRY principle. Is there any way to abstract out the projection or replace it with a delegate? I.e. replace the code firstProp = h.StringProp1, secondProp = h.StringProp2 with something reusable?

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• linq to sql using foreign keys returning iqueryable(of myEntity]

  - by Gern Blandston

  I'm trying to use Linq to SQL to return an IQueryable(of Project) when using foreign key relationships. Using the below schema, I want to be able to pass in a UserId and get all the projects created for the company the user is associated with. DB tables: Projects Projid ProjCreator FK (UserId from UserInfo table) Companyid FK (CompanyID from Companies table) UserInfo UserID PK Companyid FK Companies CompanyId PK Description I can get the iqueryable(of project) when simply getting the ProjectCreator with this: Return (From p In db.Projects _ Where p.ProjectCreator = Me.UserId) But I'm having trouble getting the syntax to get a iqueryable(of projects) when using foreign keys. Below gives me an IQueryable(of anonymous) but I can't seem to convince it to give me an IQueryable(of project) even if I try to cast it: Dim retval = (From p In db.Projects _ Join c In db.Companies On p.CompanyId Equals c.CompanyId _ Join u In db.UserInfos On u.CompanyId Equals c.CompanyId _ Where u.Login = UserId)

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• How to Expression.Invoke an arbitrary LINQ 2 SQL Query

  - by Remus Rusanu

  Say I take an arbitrary LINQ2SQL query's Expression, is it possible to invoke it somehow? MyContext ctx1 = new MyContext("..."); var q = from t in ctx1.table1 where t.id = 1 select t; Expression qe = q.Expression; var res = Expression.Invoke(qe); This throws ArgumentException "Expression of type System.Linq.IQueryable`1[...]' cannot be invoked". My ultimate goal is to evaluate the same query on several different data contexts.

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• How to turn this linq query to lazy loading

  - by Luke101

  I would like to make a certain select item to lazy load latter in my linq query. Here is my query 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_votecount, FavoriteCount = context.PostVotes.Where(x => x.PostVote_postid == p.post_id).Count() //this should load latter }; I have deleted the FavoriteCount item in the select query and would like it to ba added later based on certain conditions. Here is the way I have it lazy loaded if (GetFavoriteInfo) { posts = posts.Select(x => new { FavoriteCount = context.PostVotes.Where(y => y.PostVote_postid == x.post_id).Count() }); } I am getting a syntax error with this the above query. How do I fix this

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• VB.NET LINQ Result Set Manipulation.

  - by davemackey

  I have a table that looks like this: ID / Description / textValue / dateValue / timeValue / Type 1 / FRRSD / NULL / 2010-04-16 00:00:00.000 / NULL / classdates Now I've got a LINQ command to pull only the rows where the type is classdates from this table: Dim dbGetRegisterDates As New dcConfigDataContext Dim getDates = (From p In dbGetRegisterDates.webConfigOptions _ Where p.Type = "classdates" _ Select p) I now want to display the data in five different labels like so: lblClass1.Text = "Your class is from " & getDates.Description("FRRSD").dateValue & "to " & getDates.Description("FRRCD").dateValue Basically, I want to pull a row based on the description column value and then return the datevalue column value from that same row.

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• Custom Grid LINQ to SQL help

  - by user488361

  Following is my custome cotrol grid... public partial class LinqGrid : UserControl { object tmpDataTable = new object(); public LinqGrid() { InitializeComponent(); } public void Bind(System.Data.Linq.Table listSource) where T : class { Project.dbClassesDataContext dbc = new Project.dbClassesDataContext(); tmpDataTable = listSource; var query = (from c in listSource select c); dgvRecords.DataSource = query.Take(10).ToList(); } private void btnNext_Click(object sender, EventArgs e) { // now what i have to do here if i want next 10 records.....means how to retrive tmpDataTable object here... ??? i can't find Type of variable....?? plz help me.... } }

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• Handling auto-incrementing IDENTITY SQL Server fields with LINQ to SQL in C#

  - by Maxim Z.

  I'm building an ASP.NET MVC site that uses LINQ to SQL to connect to SQL Server, where I have a table that has an IDENTITY bigint primary key column that represents an ID. In one of my code methods, I need to create an object of that table to get its ID, which I will place into another object based on another table (FK-to-PK relationship). At what point is the IDENTITY column value generated and how can I obtain it from my code? Is the right approach to: Create the object that has the IDENTITY column Do an InsertOnSubmit() and SubmitChanges() to submit the object to the database table Get the value of the ID property of the object

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• LINQ-to-SQL class doesn't implement INotifyPropertyChanging & INotifyPropertyChanged if pulling from

  - by Traples

  I modified my data source in my LINQ-to-SQL class (by the old delete and drag back in method), and was surprised to see the INotifyPropertyChanging & INotifyPropertyChanged interfaces no longer implemented in the generated classes (MyDb.designer.cs). The methods for the individual fields went from looking like this... [Column(Storage="_Size", DbType="NVarChar(100)")] public string Size { get { return this._Size; } set { if ((this._Size != value)) { this.OnSizeChanging(value); this.SendPropertyChanging(); this._Size = value; this.SendPropertyChanged("Size"); this.OnSizeChanged(); } } } To looking like this... [Column(Storage="_Size", DbType="NVarChar(100)")] public string Size { get { return this._Size; } set { if ((this._Size != value)) { this._Size = value; } } } Any ideas on why this happens and how it will affect my application?

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• LINQ-to-SQL: Searching against a CSV

  - by Peter Bridger

  I'm using LINQtoSQL and I want to return a list of matching records for a CSV contains a list of IDs to match. The following code is my starting point, having turned a CSV string in a string array, then into a generic list (which I thought LINQ would like) - but it doesn't: Error Error 22 Operator '==' cannot be applied to operands of type 'int' and 'System.Collections.Generic.List<int>' C:\Documents and Settings\....\Search.cs 41 42 C:\...\ Code DataContext db = new DataContext(); List<int> geographyList = new List<int>( Convert.ToInt32(geography.Split(',')) ); var geographyMatches = from cg in db.ContactGeographies where cg.GeographyId == geographyList select new { cg.ContactId }; Where do I go from here?

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• Combining 2 Linq queries into 1

  - by Mike Fielden

  Given the following information, how can I combine these 2 linq queries into 1. Having a bit of trouble with the join statement. 'projectDetails' is just a list of ProjectDetails ProjectDetails (1 to many) PCardAuthorizations ProjectDetails (1 to many) ExpenditureDetails Notice I am grouping by the same information and selecting the same type of information var pCardAccount = from c in PCardAuthorizations where projectDetails.Contains(c.ProjectDetail) && c.RequestStatusId == 2 group c by new { c.ProjectDetail, c.ProgramFund } into g select new { Key = g.Key, Sum = g.Sum(x => x.Amount) }; var expenditures = from d in ExpenditureDetails where projectDetails.Contains(d.ProjectDetails) && d.Expenditures.ExpenditureTypeEnum == 0 group d by new { d.ProjectDetails, d.ProgramFunds } into g select new { Key = g.Key, Sum = g.Sum(y => y.ExpenditureAmounts.FirstOrDefault(a => a.IsCurrent && !a.RequiresAudit).CommittedMonthlyRecords.ProjectedEac) };

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