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• Updating Many-to-Many relationship with LinqToSQL

  - by Noffie

  If I had, for example, a Many-to-Many mapping table called "RolesToUsers" between a Users and an Roles table, here is how I do it: // DataContext is db, usr is a User entity // newUserRolesMappings is a collection with the desired new mappings, probably // derived by looking at selections in a checkbox list of Roles on a User Edit page db.RolesToUsers.DeleteAllOnSubmit(usr.RolesToUsers); usr.RolesToUsers.Clear(); usr.RolesToUsers.AddRange(newUserRolesMappings); I used the SQL profiler once, and this seems to generate very intelligent SQL - it will only drop the rows which are no longer in the mapping relationship, and only add rows which did not already exist in the relationship. It doesn't blindly do a complete clearing and re-construction of the relationship, as I thought it would. The internet is surprisingly quiet on the subject, and the query "LinqToSQL many-to-many" mostly just turns up articles about how the LinqToSQL data mapper doesn't "support" it very well. How does everyone else update many-to-many with LinqToSQL?

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• Compiled query using list of class objects in C#

  - by Sukan

  Hello , Can somebody help me out in creating compiled queries where input is to be a list of class objects? I have seen examples where Func<DataContext, somematchobject, IQueryable<T>> is created and compiled. But can I do something like Func<List<T>, matchObject, T>, and compile it? Basically I want an object(T) meeting certain conditions (as in matchObject) to be returned from a list of objects(List<T>). Will CompiledQuery.Compile help me in this? Please help me experts!!

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• How to Solve this Error "Cannot convert lambda expression to type 'string' because it is not a deleg

  - by peace

  . I get this error: "Cannot convert lambda expression to type 'string' because it is not a delegate type" - keyword select become underlined in blue Can you please advice. Employee emp = new Employee(); comHandledBySQt.DataSource = from x in emp.GetDataFromTable("1") select new { x.Id, Name = x.FirstName + " " + x.LastName }; comHandledBySQt.DisplayMember = "Name"; comHandledBySQt.ValueMember = "Id"; Above code should displays drop list of employees first name and last name in a combo box

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• association of more than one model to a listview

  - by Veer

  I have 3 Tables in my database. Each table has 3 fields each, excluding the ID field. out of which 2 fields are of type nvarchar. None of the tables are related. My ListView in the application helps the user to search my database, the search being incremental. The search includes the nvarchar fields of the 3 tables ie, 6 fields in total. Eg: PhoneBook: Name, PhoneNo Notes: Title, Content Bookmarks: Name, url I've the models generated for the 3 tables. Now the ListBox should display the Ph.Name, Title and the Bo.Name fields. ie, It should be bound to them. But they are from different models. I also should be able to perform CRUD operation on the item searched. How would i do that? P.S: Separate ViewModels are created for each Model which are used for their respective views for handling those tables individually. But this is an integrated view where the user should be able to search everything. Also please somebody suggest me a better Title for this question:)

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• Linq2Sql How to write outer join query?

  - by Malcolm

  Hi, I have following SQL tables. ImportantMessages impID Message ImportantMessageUsers imuID imuUserID imuImpID I want to write a Linq2Sql query so that it returns any rows from ImportantMessages that does not have a record in ImportantMessagesUsers. Matchiing fields are impID ----- imuImpID Assume imuUserID of 6

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• Why can't you return a List from a Compiled Query?

  - by Andrew

  I was speeding up my app by using compiled queries for queries which were getting hit over and over. I tried to implement it like this: Function Select(ByVal fk_id As Integer) As List(SomeEntity) Using db As New DataContext() db.ObjectTrackingEnabled = False Return CompiledSelect(db, fk_id) End Using End Function Shared CompiledSelect As Func(Of DataContext, Integer, List(Of SomeEntity)) = _ CompiledQuery.Compile(Function(db As DataContext, fk_id As Integer) _ (From u In db.SomeEntities _ Where u.SomeLinkedEntity.ID = fk_id _ Select u).ToList()) This did not work and I got this error message: Type : System.ArgumentNullException, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089 Message : Value cannot be null. Parameter name: value However, when I changed my compiled query to return IQueryable instead of List like so: Function Select(ByVal fk_id As Integer) As List(SomeEntity) Using db As New DataContext() db.ObjectTrackingEnabled = False Return CompiledSelect(db, fk_id).ToList() End Using End Function Shared CompiledSelect As Func(Of DataContext, Integer, IQueryable(Of SomeEntity)) = _ CompiledQuery.Compile(Function(db As DataContext, fk_id As Integer) _ From u In db.SomeEntities _ Where u.SomeLinkedEntity.ID = fk_id _ Select u) It worked fine. Can anyone shed any light as to why this is? BTW, compiled queries rock! They sped up my app by a factor of 2.

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• Beginner Question on traversing a EF4 model

  - by user564577

  I have a basic EF4 model with two entities. I'm using Self Tracking Entities Client has ClientAddresses relationship on clientkey = clientkey. (1 to many) How do i get a list/collection of client entities (STE) and their addresses (STE) but only ones where they live in a particular state or some such filter on the address??? This seems to filter and bring back clients but doesnt bring back addresses. var j = from client in context.Clients where client.ClientAddresses.All(c => c.ZIP == "80923") select client; I cant get this to create the Addresses because ClientAddresses is IEnumerable and it needs a TrackableCollection var query = from t1 in context.Clients join t2 in context.ClientAddresses on t1.ClientKey equals t2.ClientKey where t2.ZIP == "80923" select new Client { FirstName = t1.FirstName, LastName = t1.LastName, IsEnabled = t1.IsEnabled, ClientKey = t1.ClientKey, ChangeUser = t1.ChangeUser, ChangeDate = t1.ChangeDate, ClientAddresses = from a in t1.ClientAddresses select new ClientAddress { AddressKey = a.AddressKey, AddressLine1 = a.AddressLine1, AddressLine2 = a.AddressLine2, AddressTypeCode = a.AddressTypeCode, City = a.City, ClientKey = a.ClientKey, State = a.State, ZIP = a.ZIP } }; Any pointers would be appreciated. Thanks Edit: This seems to work.... var j = from client in context.Clients.Include("ClientAddresses") where client.ClientAddresses.Any(c => c.ZIP == "80923") select client;

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• Updating an object with L2S with ASP.NET MVC

  - by Paul

  Is there an easier way to update an object with L2S other then doing it property by property? This is what I am doing now: Public ActionResult Edit(Object obj) { var objToUpdate = _repository.Single<Object>(o => o.id = obj.id); objToUpdate.Prop1 = obj.Prob1; objToUpdate.Prop2 = obj.Prop2; ... _repository.SubmitChanges(); } I am hoping there is a way to just say objToUpdate = obj then submit the changes??? Any help on this would be appreciated!

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• L2S DataContext out of synch: row not found or changed

  - by awrigley

  The Problem I am getting a number of errors that imply that the DataContext, or rather, the way I am using the DataContext is getting out of synch. The error occurs on db.SubmitChanges() where db is my DataContext instance. The error is: Row not found or changed. The problem only occurs intermitently, for example, adding a row then deleting it. If I stop the dev server and restart, the added row is there and I can delete it no problem. Ie, it seems that the problem is related to the DataContext losing track of the rows that have been added. IMPORTANT: Before anyone votes to close this thread, on the basis of it being a duplicate, I have checked the sql server profiler and there is no "Where 0 = 1" in the SQL. I have also recreated the dbml file, so am satisfied that the database schema is in synch with the schema represented by the dbml file. Ie, no cases of mismatched nullable/not nullable columns, etc. My Diagnosis (for what it is worth): It seems to be a problem related to how I am using the DataContext. I am new to MVC, Repositories and Services patterns, so suspect that I have wired things up wrong. The Setup Simple eLearning app in its early stages. Pupils need to be able to add and delete courses (Courses table) to their UserCourses. To do this, I have a service that gets a specific DataContext instance Dependency Injected into its constructor. Service Class Constructor: public class SqlPupilBlockService : IPupilBlockService { DataContext db; public SqlPupilBlockService(DataContext db) { this.db = db; CoursesRepository = new SqlRepository<Course>(db); UserCoursesRepository = new SqlRepository<UserCourse>(db); } // Etc, etc } The CoursesRepository and UserCoursesRepository are both private properties of the service class that are of Type IRepository (just a simple generic repository interface). Sql Respoitory Code: public class SqlRepository<T> : IRepository<T> where T : class { DataContext db; public SqlRepository(DataContext db) { this.db = db; } #region IRepository<T> Members public IQueryable<T> Query { get { return db.GetTable<T>(); } } public List<T> FetchAll() { return Query.ToList(); } public void Add(T entity) { db.GetTable<T>().InsertOnSubmit(entity); } public void Delete(T entity) { db.GetTable<T>().DeleteOnSubmit(entity); } public void Save() { db.SubmitChanges(); } #endregion } The two methods for adding and deleting UserCourses are: Service Methods for Adding and Deleting UserCourses: public void AddUserCourse(int courseId) { UserCourse uc = new UserCourse(); uc.IdCourse = courseId; uc.IdUser = UserId; uc.DateCreated = DateTime.Now; uc.DateAmended = DateTime.Now; uc.Role = "Pupil"; uc.CourseNotes = string.Empty; uc.ActiveStepIndex = 0; UserCoursesRepository.Add(uc); UserCoursesRepository.Save(); } public void DeleteUserCourse(int courseId) { var uc = (UserCoursesRepository.Query.Where(x => x.IdUser == UserId && x.IdCourse == courseId)).Single(); UserCoursesRepository.Delete(uc); UserCoursesRepository.Save(); } Ajax I am using Ajax via Ajax.BeginForm I don't think that is relevant. ASP.NET MVC 3 I am using mvc3, but don't think that is relevant: the errors are related to model code.

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• Generate Numbers and Select in memory

  - by Jasl

  I want to do the following dynamically Generate numbers from 1 to 100 and then select 25 random numbers from it and display it in a console. Any easy way to do so?

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• initializing properties with private sets in .Net

  - by Martin Neal

  public class Foo { public string Name { get; private set;} // <-- Because set is private, } void Main() { var bar = new Foo {Name = "baz"}; // <-- This doesn't compile /*The property or indexer 'UserQuery.Foo.Name' cannot be used in this context because the set accessor is inaccessible*/ using (DataContext dc = new DataContext(Connection)) { // yet the following line works. **How**? IEnumerable<Foo> qux = dc.ExecuteQuery<Foo>( "SELECT Name FROM Customer"); } foreach (q in qux) Console.WriteLine(q); } I have just been using the private modifier because it works and kept me from being stupid with my code, but now that I need to create a new Foo, I've just removed the private modifier from my property. I'm just really curious, why does the ExecuteQuery into an IEnumerable of Foo's work?

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• Eager loading in EF1.0

  - by Dave Swersky

  I have a many-to-many relationship: Application - Applications_Servers - Server This is set up in my Entity Data Model and all is well. My problem is that I'd like to eager-load the whole graph of Applications so that I have an IEnumerable<Applications>, each Application member populated with the Servers collection associated by the many-to-many relationship. Normally this wouldn't be a problem, but according to my research there must be a navigation property between Application and Server. This is not the case for me because my Applications_Servers join table has more in it than just the two keys. Therefore, there is no navigation property directly between Application and Server, and this doesn't work: var apps = (from a in context.Application.Include("Server") select a).ToList(); I get an error saying there is no navigation property on Application called "Server", and that's correct, there is none. How do I write the query to eager-load my Applications with their Servers in this case?

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• ToList()-- Does it Create a New List?

  - by Ngu Soon Hui

  Let's say I have a class public class MyObject { public int SimpleInt{get;set;} } And I have a List<MyObject>, and I ToList() it and then change one of the SimpleInt, will my change be propagated back to the original list. In other words, what would be the output of the following method? public void RunChangeList() { var objs = new List<MyObject>(){new MyObject(){SimpleInt=0}}; var whatInt = ChangeToList(objs ); } public int ChangeToList(List<MyObject> objects) { var objectList = objects.ToList(); objectList[0].SimpleInt=5; return objects[0].SimpleInt; } Why? P/S: I'm sorry if it seems obvious to find out. But I don't have compiler with me now...

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• Lambda expressions and nullable types

  - by Mathew

  I have two samples of code. One works and returns the correct result, one throws a null reference exception. What's the difference? I know there's some magic happening with capturing variables for the lambda expression but I don't understand what's going on behind the scenes here. int? x = null; bool isXNull = !x.HasValue; // this works var result = from p in data.Program where (isXNull) select p; return result.Tolist(); // this doesn't var result2 = from p in data.Program where (!x.HasValue) select p; return result2.ToList();

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• Losing scope for DataContex using LINQToSQL intermediately

  - by greektreat

  I am having a weird Situation with my DataConext. All My code is in C# I have a DLL project for my data access layer and business Layer which and Winforms project for my UI layer. My Data access Layer's Namespace is xxx.Data this is where have my xxx.dbml I also have xxx.Data.BusinessObjects name space of course for my business object in that project In my UI Layer I have these namespaces xxxApp(for Forms), xxxApp.Controls (For Controls) I have lost scope of the DataContext, it was accessible now when I do a Rebuild Solution I sometimes get compile errors saying for example: Error 34 'xxx.Data.xxxDataContext' does not contain a definition for 'SubmitChanges' and no extension method 'SubmitChanges' accepting a first argument of type 'xxx.Data.xxxDataContext' could be found (are you missing a using directive or an assembly reference?) Also intelisense doesn't recognize the methods and table classes from my xxxDataContext anymore I can access all object fine when I am in the DLL project but now in the Winforms project this is very strange. If anyone can help me out I would be extremely grateful!

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• StreamInsight complex query with filter on HoppingWindow

  - by hh354

  I'm trying out StreamInsight and I came across a problem with a query I need. I'm trying to throw a warning if there are several changes in my measured values (of up to 20% change) in the last 30 minutes. This is the query I came up with for now but it isn't working and it's not even correct I think. Apparently I can't filter on a window...? var deviationQuery = from s in wcfStream group s by s.SensorId into grouped from window in grouped.HoppingWindow(TimeSpan.FromMinutes(30),TimeSpan.FromMinutes(1)) where window.StdDev(e => e.Value) > measurableValue * 1.2 select new OutputEvent { Error = "Deviation" }; Thanks in advance!

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• Distinct items from IEnumerable< T>

  - by ScG

  I have an IEnumerable< Person object. The Person class has a Designation proeprty. I want to select distinct Designation values from IEnumerable< Person and assign that to a DropDownList. How can I do it?

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• Updating database row from model

  - by Jamie Dixon

  Hey everyone, I'm haing a few problems updating a row in my database using Linq2Sql. Inside of my model I have two methods for updating and saving from my controller, which in turn receives an updated model from my view. My model methods like like: public void Update(Activity activity) { _db.Activities.InsertOnSubmit(activity); } public void Save() { _db.SubmitChanges(); } and the code in my Controller likes like: [HttpPost] public ActionResult Edit(Activity activity) { if (ModelState.IsValid) { UpdateModel<Activity>(activity); _activitiesModel.Update(activity); _activitiesModel.Save(); } return View(activity); } The problem I'm having is that this code inserts a new entry into the database, even though the model item i'm inserting-on-submit contains a primary key field. I've also tried re-attaching the model object back to the data source but this throws an error because the item already exists. Any pointers in the right direction will be greatly appreciated. UPDATE: I'm using dependancy injection to instantiate my datacontext object as follows: IMyDataContext _db; public ActivitiesModel(IMyDataContext db) { _db = db; }

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• Matching on search attributes selected by customer on front end

  - by CodeNinja1974

  I have a method in a class that allows me to return results based on a certain set of Customer specified criteria. The method matches what the Customer specifies on the front end with each item in a collection that comes from the database. In cases where the customer does not specify any of the attributes, the ID of the attibute is passed into the method being equal to 0 (The database has an identity on all tables that is seeded at 1 and is incremental). In this case that attribute should be ignored, for example if the Customer does not specify the Location then customerSearchCriteria.LocationID = 0 coming into the method. The matching would then match on the other attributes and return all Locations matching the other attibutes, example below: public IEnumerable<Pet> FindPetsMatchingCustomerCriteria(CustomerPetSearchCriteria customerSearchCriteria) { if(customerSearchCriteria.LocationID == 0) { return repository.GetAllPetsLinkedCriteria() .Where(x => x.TypeID == customerSearchCriteria.TypeID && x.FeedingMethodID == customerSearchCriteria.FeedingMethodID && x.FlyAblityID == customerSearchCriteria.FlyAblityID ) .Select(y => y.Pet); } } The code for when all criteria is specified is shown below: private PetsRepository repository = new PetsRepository(); public IEnumerable<Pet> FindPetsMatchingCustomerCriteria(CustomerPetSearchCriteria customerSearchCriteria) { return repository.GetAllPetsLinkedCriteria() .Where(x => x.TypeID == customerSearchCriteria.TypeID && x.FeedingMethodID == customerSearchCriteria.FeedingMethodID && x.FlyAblityID == customerSearchCriteria.FlyAblityID && x.LocationID == customerSearchCriteria.LocationID ) .Select(y => y.Pet); } I want to avoid having a whole set of if and else statements to cater for each time the Customer does not explicitly select an attribute of the results they are looking for. What is the most succint and efficient way in which I could achieve this?

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• How to perform a select using a WHERE NOT EXISTS

  - by Peter Bridger

  I'm using LINQ2SQL and I want to compare two tables and select all rows that are missing from one tables (based upon one of the column values). In standard SQL I would write this as: SELECT FirstName, LastName, RefId, Email FROM Users_ActiveDirectory AS ADU WHERE NOT EXISTS ( SELECT U.RefId FROM Users AS U WHERE U.RefID = ADU.RefId ) However I'm not sure how to achieve the same result using LINQ2SQL?

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• Where is the best place to call the .tolist(); inside my controller classes or inside my model repository classes

  - by john G

  I have the following action method, inside my asp.net mvc web application:- public JsonResult LoadZoneByDataCenter(string id) { var zonelist = repository.getrealtedzone(Convert.ToInt32(id)).ToList(); //code goes here Which calls the following model repository method:- public IQueryable<Zone> getrealtedzone(int? dcid) { return tms.Zones.Where(a=> a.DataCenterID == dcid || dcid == null); } Currently I am calling the .tolist() which will interpret the Database from my action method, but my question is where is the best place to call the .tolist() inside the controller or inside the model classes and why ? thanks

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• How to return a message from my repository class to my controller and then to my view in asp.net-mvc

  - by Pandiya Chendur

  I use this for checking an existing emailId in my table and inserting it...It works fine how to show message to user when he tries to register with an existing mailId.... if (!taxidb.Registrations.Where(u => u.EmailId == reg.EmailId).Any()) { taxidb.Registrations.InsertOnSubmit(reg); taxidb.SubmitChanges(); } and my controller has this, RegistrationBO reg = new RegistrationBO(); reg.UserName = collection["UserName"]; reg.OrgName = collection["OrgName"]; reg.Address = collection["Address"]; reg.EmailId = collection["EmailId"]; reg.Password = collection["Password"]; reg.CreatedDate = System.DateTime.Now; reg.IsDeleted = Convert.ToByte(0); regrep.registerUser(reg); Any sugesstion how to show "EmailID" already exists to the user with asp.net mvc...

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• DataContext to DB

  - by JD

  Hi all, I have designed my DB using the ORM in VS 2008. What is the best way to export this to an SQL server so it will create the tables and relations on SQL Server? Thanks, JD

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• How can I find all items beginning with a or â?

  - by Malcolm Frexner

  I have a list of items that are grouped by their first letter. By clicking a letter the user gets alle entries that begin with that letter. This does not work for french. If I choose the letter a, items with â are not returned. What is a good way to return items no matter if they have an accent or not? <% char alphaStart = Char.Parse("A"); char alphaEnd = Char.Parse("Z"); %> <% for (char i = alphaStart; i <= alphaEnd; i++) { %> <% char c = i; %> <% var abcList = Model.FaqList.Where(x => x.CmsHeader.StartsWith(c.ToString())).ToList(); %> <% if (abcList.Count > 0 ) { %> <div class="naviPkt"> <a id="<%= i.ToString().ToUpper() %>" class="naviPktLetter" href="#<%= i.ToString().ToLower() %>"><%= i.ToString().ToUpper() %></a> </div> <ul id="menuGroup<%= i.ToString().ToUpper() %>" class="contextMenu" style="display:none;"> <% foreach (var info in abcList) { %> <li class="<%= info.CmsHeader%>"> <a id="infoId<%= info.CmsInfoId%>" href="#<%= info.CmsInfoId%>" class="abcEntry"><%= info.CmsHeader%></a> </li> <% } %> </ul> <% } %> <% } %>

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• Quickly or concisely determine the longest string per column in a row-based data collection

  - by ccornet

  Judging from the failure of my last inquiry, I need to calculate and preset the widths of a set of columns in a table that is being made into an Excel file. Unfortunately, the string data is stored in a row-based format, but the widths must be calculated in a column-based format. The data for the spreadsheets are generated from the following two collections: var dictFiles = l.Items.Cast<SPListItem>().GroupBy(foo => foo.GetSafeSPValue("Category")).ToDictionary(bar => bar.Key); StringDictionary dictCols = GetColumnsForItem(l.Title); Where l is an SPList whose title determines which columns are used. Each SPListItem corresponds to a row of data, which are sorted into separate worksheets based on Category (hence the dictionary). The second line is just a simple StringDictionary that has the column name (A, B, C, etc.) as a key and the corresponding SPListItme field display name as the corresponding value. So for each Category, I enumerate through dictFiles[somekey] to get all the rows in that sheet, and get the particular cell data using SPListItem.Fields[dictCols[colName]]. What I am asking is, is there a quick or concise method, for any one dictFiles[somekey], to retrieve a readout of the longest string in each column provided by dictCols? If it is impossible to get both quickness and conciseness, I can settle for either (since I always have the O(n*m) route of just enumerating the collection and updating an array whenever strCurrent.Length strLongest.Length). For example, if the goal table was the following... Item# Field1 Field2 Field3 1 Oarfish Atmosphere Pretty 2 Raven Radiation Adorable 3 Sunflower Flowers Cute I'd like a function which could cleanly take the collection of items 1, 2, and 3 and output in the correct order... Sunflower, Atmosphere, Adorable Using .NET 3.5 and C# 3.0.

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