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  • Linq to SQL inheritance and Table per Class - approach needed for multiple roles

    - by Ash Machine
    I am using L2S and an inheritance model for mapping Persons against certain roles. Guy Burstein's excellent blog post explains how to accomplish this: http://blogs.microsoft.co.il/blogs/bursteg/archive/2007/10/01/linq-to-sql-inheritance.aspx However, I have a specific case where a Person has multiple roles. For example 'Jane Doe' is a Contact and a Programmer. In this model, she would need two rows in the People table, one as Contact (PersonType = 1) and one as Programmer (PersonType = 3). If she changes her last name, and that update happens in her role as Contact, I would need to change all instances of 'Jane Doe' to reflect the name change everywhere. What sort of best approach (improved data structure) could be used to change last name within all roles? Finally, I am hoping to avoid overriding each general form update events to include all instances, but that may be the only way. Any suggestions or approaches appreciated.

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  • Using multiple databases within one application (ASP.NET MVC, LINQ to SQL)

    - by Alex
    I have a web application made for several groups of people not connected with each other. Instead of using one database for all of them, I'm thinking about making separate databases. This will improve the speed of the queries and make me free from checking to what group the user belongs. But since I'm working with LINQ to SQL, my classes are explicitly connected with the databases, so I will have to make separate DataContexts for all of the databases. So how can I solve this problem? Or should I just not bother and use one database only?

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  • LINQ - Using where or join - Performance difference ?

    - by Patrick Säuerl
    Hi Based on this question: http://stackoverflow.com/questions/3013034/what-is-difference-between-where-and-join-in-linq My question is following: Is there a performance difference in the following two statements: from order in myDB.OrdersSet from person in myDB.PersonSet from product in myDB.ProductSet where order.Persons_Id==person.Id && order.Products_Id==product.Id select new { order.Id, person.Name, person.SurName, product.Model,UrunAdi=product.Name }; and from order in myDB.OrdersSet join person in myDB.PersonSet on order.Persons_Id equals person.Id join product in myDB.ProductSet on order.Products_Id equals product.Id select new { order.Id, person.Name, person.SurName, product.Model,UrunAdi=product.Name }; I would always use the second one just because it´s more clear. My question is now, is the first one slower than the second one? Does it build a cartesic product and filters it afterwards with the where clauses ? Thank you.

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  • Creating LINQ to SQL for counting a parameter

    - by Matt
    I'm trying to translate a sql query into LINQ to SQL. I keep getting an error "sequence operators not supported for type 'system.string'" If I take out the distinct count part, it works. Is it not because I'm using the GROUP BY? SELECT COUNT(EpaValue) AS [Leak Count], Location, EpaValue AS [Leak Desc.] FROM ChartMes.dbo.RecourceActualEPA_Report WHERE (EpaName = N'LEAK1') AND (Timestamp) '20100429030000' GROUP BY EpaValue, Location ORDER BY Location, [Leak Count] DESC Dim temp = (From p In db2.RecourceActualEPA_Reports _ Where (p.Timestamp = str1stShiftStart) And (p.Timestamp < str2ndShiftCutoff) _ And (p.EpaName = "Leak1") _ Select p.EpaName.Distinct.Count(), p.Location, p.EpaValue)

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  • Linq to SQl Stored Procedure Problem( it can't figure out the return type)

    - by chobo2
    Hi I have this SP USE [Test] GO SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO CREATE PROCEDURE [dbo].[UsersInsert](@UpdatedProdData XML) AS INSERT INTO dbo.UserTable(UserId,UserName,LicenseId,Password,PasswordSalt,Email,IsApproved,IsLockedOut,CreateDate, LastLoginDate,LastLockOutDate,FailedPasswordAttempts,RoleId) SELECT @UpdatedProdData.value('(/ArrayOfUsers/Users/UserId)[1]', 'uniqueidentifier'), @UpdatedProdData.value('(/ArrayOfUsers/Users/UserName)[1]', 'varchar(20)'), @UpdatedProdData.value('(/ArrayOfUsers/Users/LicenseId)[1]', 'varchar(50)'), @UpdatedProdData.value('(/ArrayOfUsers/Users/Password)[1]', 'varchar(128)'), @UpdatedProdData.value('(/ArrayOfUsers/Users/PasswordSalt)[1]', 'varchar(128)'), @UpdatedProdData.value('(/ArrayOfUsers/Users/Email)[1]', 'varchar(50)'), @UpdatedProdData.value('(/ArrayOfUsers/Users/IsApproved)[1]', 'bit'), @UpdatedProdData.value('(/ArrayOfUsers/Users/IsLockedOut)[1]', 'bit'), @UpdatedProdData.value('(/ArrayOfUsers/Users/CreateDate)[1]', 'datetime'), @UpdatedProdData.value('(/ArrayOfUsers/Users/LastLoginDate)[1]', 'datetime'), @UpdatedProdData.value('(/ArrayOfUsers/Users/LastLockOutDate)[1]', 'datetime'), @UpdatedProdData.value('(/ArrayOfUsers/Users/FailedPasswordAttempts)[1]', 'int'), @UpdatedProdData.value('(/ArrayOfUsers/Users/RoleId)[1]', 'int') Now this SP creates just fine. It's when I go to VS2010 and try to drag this SP in my method panel of my linq to sql file in design view. It tells me that it can't figure out the return type. I try to go to the properties but it does not have "none" as a choice and I can't type it in. It should be "none" so how do I set it to "none"?

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  • Linq to SQL - design question.

    - by UshaP
    HI, Currently i have one big datacontex with 35 tables (i dragged all my DB tables to the designer). I must admit it is very comfortable cause i have ORM to my full DB and query with linq is easy and simple. My questions are: 1. Would you consider it bad design to have one datacontext with 35 tables or should i split it to logic units? 2. Is there any performance penalties for using such a big datacontext? Thanks, Pini.

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  • 'Recursive' LINQ calls

    - by Sir Psycho
    Hi, I'm trying to build an XML tree of some data with a parent child relationship, but in the same table. The two fields of importance are CompetitionID ParentCompetitionID Some data might be CompetitionID=1, ParentCompetitionID=null CompetitionID=2, ParentCompetitionID=1 CompetitionID=3, ParentCompetitionID=1 The broken query I have simply displays results in a flat format. Seeing that I'm working with XML, some sort of recursive functionality is required. I can do this using recursion, but would like to see the linq version. Any help appreciated. var results = from c1 in comps select new { c.CompetitionID, SubComps= from sc in comps.Where (c2 => c2.CompetitionID == c1.CompetitionID) select sc };

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  • Neat way of gettings position of my Object in linq collections

    - by Steve
    I currently have a object called Week. A week is part of a Season object. the season can contain many weeks. What I want to do is find the position of my week (is it the first week in the season (so #1) or is it the second (so #2). int i = 0; foreach ( var w in Season.Weeks.OrderBy(w => w.WeekStarts)){ if(w.Id == Id){ return i; } i+=1; } At the moment this is what I have. I order the weeks in a second by there start date to make sure they are in the correct order. and I cycle through them until I find the week that matches the week I am currently looking at. and return the int that I have been counting up.. I feel there should be a easier linq way to do this as it feels pretty messy!

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  • Is it possible to create custom methods in entity classes in linq to sql

    - by doekman
    I have a table Site in SQL with (amongst others) three properties idReviewer1, idReviewer2, idReviewer3. Now I would like to create a methods on the entity class of Site to check if a user is a reviewer: partial class Site { public bool IsReviewer(int idUser) { return idReviewer1 == idUser || idReviewer2 == idUser || idReviewer3 == idUser; } } and I use it like this: return from s in db.Sites where s.IsReviewer(user) select s; However, Linq to SQL doesn't know how to translate this to SQL. I get the following error message: Method 'Boolean IsReviewer(Int32)' has no supported translation to SQL. I'd rather not write this: return from s in db.Sites where idReviewer1 == idUser || idReviewer2 == idUser || idReviewer3 == idUser select s; Is there any way to put this functionality in one place, without resorting to SQL?

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  • Select a Column Dynamically using LINQ?

    - by vsj
    Hi all I am trying to do a very simple dynamic query which will select a column dynamically I mean the selection of column would depend upon another query so I would select x col if cond1 and y if cond2 so I tried using query.Select(colname) using the extension method also tried using Func< but I am not sure how to go about this I have read about dynamic extension for linq and also reflection but woth reflection to the GetValue function does not return value for my column in database. please help me out I am jus trying to select a column dynamically at runtime and no condtions really on it.

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  • Linq to SQL and Realtime Data

    - by Jeremy
    I have an application that needs to constantly (every 50ms), call to an MVC action, and pickup/drop off data. I am using Linq to SQL and MVC because of how simple they are to implement, and I know that they aren't perfect when it comes to performance, but it works relatively well, but the best speed I can get with my current approach is 200ms (without requests overlapping). Each call to the site will create a new instance of the datacontext, query/insert it and return that data. Is there a way to have the datacontext static, but submitchanges say every 5 seconds, so that i am pretty much hitting an in-memory version of the data?

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  • Linq-to-SQL- A stored procedure returns field which is not there in Mapped Table Info

    - by jalpesh
    We are using Linq-to-SQL with stored Procedures we need help on one of our problem. We are having user tables which is having all field required for user table like firstname,lastname and other fields that table is also there in our DBML files.Now the problem is that we are having a stored procedure that is mapped to table-User returning a field called fullname (Combination of firstname and lastname)which is not there in usertable. So what is the best way to slove this. Another thing is that one of other stored procedure return inner join of two tables with mix columns in this case how can i mapped that stored procedure with Table mapped info class in our dbml files.

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  • Using a linq or lambda expression in C# return a collection plus a single value

    - by ahsteele
    I'd like to return a collection plus a single value. Presently I am using a field to create a new list adding a value to the list and then returning the result. Is there a way to do this with a linq or lambda expression? private List<ChargeDetail> _chargeBreakdown = new List<ChargeDetail>(); public ChargeDetail PrimaryChargeDetail { get; set; } public List<ChargeDetail> ChargeBreakdown { get { List<ChargeDetail> result = new List<ChargeDetail>(_chargeBreakdown); result.Add(PrimaryChargeDetail); return result; } }

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  • Safely dereferencing FirstOrDefault call in Linq c#

    - by samy
    For brevity's sake in my code, i'd like to be able to do the following: having a collection, find the first element matching a lambda expression; if it exists, return the value of a property or function. If it doesn't exist, return null. var stuff = {"I", "am", "many", "strings", "obviously"}; var UpperValueOfAString = stuff.FirstOrDefault(s => s.contains("bvi")).ToUpper(); // would return "OBVIOUSLY" var UpperValueOfAStringWannabe = stuff.FirstOrDefault(s => s.contains("unknown token")).ToUpper(); // would return null Is it possible with some linq-syntax-fu or do i have to check explicitly for the return value before proceeding?

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  • LINQ Multiple LIKE based on List

    - by Bathan
    I have a list of keywords in an ArrayList and I wanted to be able to build a query to find records in a table based on this keywords. Since the list of keywords is dynamic I cannot build a fixed query here. if I do something like this: foreach (string kw in keywords) { query = query.Where(p => p.Name.StartsWith(kw)); } The "StartsWith" is required here because I need to search those records that actually start with the provided keyword. In T-SQL it Would be something like this Select * from Table where Name like 'keyword1%' or Name like 'keyword2%' or Name like 'keyword3%' or ... But I need to be able to do this in LINQ...Is this possible?

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  • LINQ How to force query to materialize?

    - by Bobb
    Say I have simple LINQ extenstion: var filtered = data.Where(i => i.Count > 0); I know that this will not evaluated unless I start to use filtered i.e. foreach(DataItem i in filtered) ... However I need to create cloned version of data and release data as soon as possible. data can be changed in other thread so I want to get immediate snapshot of it. How can I force filtered to be evaluated immediately?

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  • Using database default values with Linq to SQL codewise

    - by Ivo
    I am using Dynamic Data with linq to SQL and SQL Server 2008. I have a GUID column that gets his value from the default value with newguid(). When I set IsDbGenerated to true in the designer it works like a charm. But when I renew table this property is set back to false again. So I added it to the metadata. For some reason it's not being pickup, "00000000-0000-0000-0000-000000000000" is being inserted in database. The displayname and readonly change are being pick up. What am I missing? [MetadataType(typeof(CMS_Data_HistoryMetadata))] public partial class CMS_Data_History { } [TableName("Content")] public class CMS_Data_HistoryMetadata { [DisplayName("Pagina Title")] public object pageTitleBar { get; set; } [ReadOnly(true)] [DisplayName("Versie")] public object version_date { get; set; } [ColumnAttribute(IsDbGenerated = true)] public object entity_id; }

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  • Need help with formulating LINQ query

    - by eponymous23
    I'm building a word anagram program that uses a database which contains one simple table: Words --------------------- varchar(15) alphagram varchar(15) anagram (other fields omitted for brevity) An alphagram is the letters of a word arranged in alphabetical order. For example, the alphagram for OVERFLOW would be EFLOORVW. Every Alphagram in my database has one or more Anagrams. Here's a sample data dump of my table: Alphagram Anagram EINORST NORITES EINORST OESTRIN EINORST ORIENTS EINORST STONIER ADEINRT ANTIRED ADEINRT DETRAIN ADEINRT TRAINED I'm trying to build a LINQ query that would return a list of Alphagrams along with their associated Anagrams. Is this possible?

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  • LINQ - if condition

    - by ile
    In code, the commented part is what I need to solve... Is there a way to write such query in LINQ? I need this because I will need sorting based on Status. var result = ( from contact in db.Contacts join user in db.Users on contact.CreatedByUserID equals user.UserID join deal in db.Deals on contact.ContactID equals deal.ContactID into deals orderby contact.ContactID descending select new ContactListView { ContactID = contact.ContactID, FirstName = contact.FirstName, LastName = contact.LastName, Email = contact.Email, Deals = deals.Count(), EstValue = deals.Sum(e => e.EstValue), SalesAgent = user.FirstName + " " + user.LastName, Tasks = 7, // This is critical part if(Deals == 0) Status = "Prospect"; else Status = "Client"; // End of critical part... }) .OrderBy(filterQuery.OrderBy + " " + filterQuery.OrderType) .Where(filterQuery.Status);

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  • Taking 2 attributes from XElement to create a dictionary LINQ

    - by AndyC
    I'm trying to take one attribute to use as the key, and another to use as the value. If I use (xDoc is an XDocument object in the example): Dictionary<string, XElement> test = xDoc.Descendants() .Where<XElement>(t => t.Name == "someelement") .ToDictionary<XElement, string>(t => t.Attribute("myattr").Value.ToString()); I get a dictionary with the myattr value as key (which is what I want) but the entire XElement object as the value. What I want to do, is to select a second attribute to set as the value property on each dictionary item, but can't seem to figure that out. Is it possible to do all of this in 1 Linq statement? Curiousity has caught me! Cheers!

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  • How to convert objects in reflection (Linq to XML)

    - by user829174
    I have the following code which is working fine, the code creates plugins in reflection via run time: using System; using System.Collections.Generic; using System.Linq; using System.IO; using System.Xml.Linq; using System.Reflection; using System.Text; namespace WindowsFormsApplication1 { public abstract class Plugin { public string Type { get; set; } public string Message { get; set; } } public class FilePlugin : Plugin { public string Path { get; set; } } public class RegsitryPlugin : Plugin { public string Key { get; set; } public string Name { get; set; } public string Value { get; set; } } static class MyProgram { [STAThread] static void Main(string[] args) { string xmlstr =@" <Client> <Plugin Type=""FilePlugin""> <Message>i am a file plugin</Message> <Path>c:\</Path> </Plugin> <Plugin Type=""RegsitryPlugin""> <Message>i am a registry plugin</Message> <Key>HKLM\Software\Microsoft</Key> <Name>Version</Name> <Value>3.5</Value> </Plugin> </Client> "; Assembly asm = Assembly.GetExecutingAssembly(); XDocument xDoc = XDocument.Load(new StringReader(xmlstr)); Plugin[] plugins = xDoc.Descendants("Plugin") .Select(plugin => { string typeName = plugin.Attribute("Type").Value; var type = asm.GetTypes().Where(t => t.Name == typeName).First(); Plugin p = Activator.CreateInstance(type) as Plugin; p.Type = typeName; foreach (var prop in plugin.Descendants()) { var pi = type.GetProperty(prop.Name.LocalName); object newVal = Convert.ChangeType(prop.Value, pi.PropertyType); pi.SetValue(p, newVal, null); } return p; }).ToArray(); // //"plugins" ready to use // } } } I am trying to modify the code and adding new class named DetailedPlugin so it will be able to read the following xml: string newXml = @" <Client> <Plugin Type=""FilePlugin""> <Message>i am a file plugin</Message> <Path>c:\</Path> <DetailedPlugin Type=""DetailedFilePlugin""> <Message>I am a detailed file plugin</Message> </DetailedPlugin> </Plugin> <Plugin Type=""RegsitryPlugin""> <Message>i am a registry plugin</Message> <Key>HKLM\Software\Microsoft</Key> <Name>Version</Name> <Value>3.5</Value> <DetailedPlugin Type=""DetailedRegsitryPlugin""> <Message>I am a detailed registry plugin</Message> </DetailedPlugin> </Plugin> </Client> "; for this i modified my classes to the following: public abstract class Plugin { public string Type { get; set; } public string Message { get; set; } public DetailedPlugin DetailedPlugin { get; set; } // new } public class FilePlugin : Plugin { public string Path { get; set; } } public class RegsitryPlugin : Plugin { public string Key { get; set; } public string Name { get; set; } public string Value { get; set; } } // new classes: public abstract class DetailedPlugin { public string Type { get; set; } public string Message { get; set; } } public class DetailedFilePlugin : Plugin { public string ExtraField1 { get; set; } } public class DetailedRegsitryPlugin : Plugin { public string ExtraField2{ get; set; } } from here i need some help to accomplish reading the xml and create the plugins with the nested DetailedPlugin

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  • Linq: comparison with nonexisting value should not cause the exception, but it does

    - by Seacat
    Hello, Given I don't know if the parameter will be null or not and I want to use it in the following way: if Param != null then compare with its id if Param == null then compare with null. Something like that: var c = from cat in context.Categories where ParamCat != null && cat.ParentId == ParamCat.Id || ParamCat == null && cat.ParentId == null select c; If ParamCat is null as soon as I try to get something from c (for example c.Count()) it throws the exception. Usually when we use some kind of condition it stop comparison as soon as condition fail especially if we use AND. For example this code will not cause any exception: if (ParamCat != null && cat.ParentId == RaramCat.Id) { } If so, why the linq code above throw exception? (Null reference) Thanks

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  • Update 2 table values in one query in LINQ

    - by fireBand
    Hello, I have 2 tables Table1 with columns [BId,Name,Amount] Table2 with columns [CId,BId, ExpenseType,Expense]. BId Is the foreign key in Table2. The Amount field in Table1 is always higher than Expense in Table2. I need to update the values of Amount (increase or decrease) based on value of Expense and I want to do it in single query in LINQ. Eg If the Expense has to be updated with 200, I would decrease(negate) Amount value with 200. If Expense is reduce to 100 then the Amount is increased by a value of 100. Thanks in advance for any suggestions.

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  • Datatable -filter records with linq based on some internal index

    - by Karan
    Hello Guys, I have a datatable with plenty of records. And i have a range like lowerRange = 10 and upperRange = 200. I want the pull the records starting at row 10 till row 200. Now i don't want to add any new index based column into the datatable. Is there any way with the help of linq, i can pull the set of rows based on some internal datatable index? I guess, the datatable must be maintaining some row index implicitly. Please suggest.

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  • Help with a algorithm in linq to resolve a query

    - by Deumber
    I have been some time thinking how to resolve this problem, but out of ideas i prefer expose it for help. I have 2 tables (linq to sql) A and B, A have a many relation with B, so A have a property EntitySet of B A have the following properties: CreateDate (Datetime) ModificateDate (Datetime) Bs (EntitySet<B>) B have the following properties: CreateDate (Datetime) ModificateDate (Datetime) All that i want is return a ordered collection of A by the Max date between : A.CreateDate, A.ModificateDate, The Max B.CreateDate of all B in A The Max B.ModificateDate of all B in A if i someone need a little example, just ask for it.

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