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  • Linqify this: Aggregate a subset of a list

    - by JMarsch
    Suppose I have a list or array of items, and I want to sum a subset of the items in the list. (in my case, it happens to always be a sequential subset). Here's the old-fashioned way: int sum = 0; for(int i = startIndex; i <= stopIndex; i++) sum += myList[i].TheValue; return sum; What's the best way to linqify that code?

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  • ASP.NET MVC- Bizarre problem - suddennly lost all LINQTO SQL data context objects

    - by MikeD
    I was making an edit to a long existing project. Specifically I added some fields to a table and had to delete the table from the LINQTOSQL designer and re-add it. doesn't Also had to do the same for a view. Mode some other code changes and went to build . Now my project won't build because it can't resolve any of the data context objects (all tables and views) in my code. I don't know what I did or how this happeened. I have many tables and views in the project's L2S data context so I don't wont to try and do over. Please any suggestions on how to resolve this problem are greatly appreciated. Desparate! The error messages I am getting are the familiar The type or namespace name 'equipment' could not be found (are you missing a using directive or an assembly reference?)

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  • Precompile Lambda Expression Tree conversions as constants?

    - by Nathan
    It is fairly common to take an Expression tree, and convert it to some other form, such as a string representation (for example this question and this question, and I suspect Linq2Sql does something similar). In many cases, perhaps even most cases, the Expression tree conversion will always be the same, i.e. if I have a function public string GenerateSomeSql(Expression<Func<TResult, TProperty>> expression) then any call with the same argument will always return the same result for example: GenerateSomeSql(x => x.Age) //suppose this will always return "select Age from Person" GenerateSomeSql(x => x.Ssn) //suppose this will always return "select Ssn from Person" So, in essence, the function call with a particular argument is really just a constant, except time is wasted at runtime re-computing it continuously. Assuming, for the sake of argument, that the conversion was sufficiently complex to cause a noticeable performance hit, is there any way to pre-compile the function call into an actual constant?

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  • How do I simulate "Is In" using Linq2Sql

    - by flipdoubt
    I often find myself with a list of disconnected Linq2Sql objects or keys that I need to re-select from a Linq2Sql data-context to update or delete in the database. If this were SQL, I would use IS IN in the SQL WHERE clause, but I am stuck with what to do in Linq2Sql. Here is a sample of what I would like to write: public void MarkValidated(IList<int> idsToValidate) { using(_Db.NewSession()) // Instatiates new DataContext { // ThatAreIn <- this is where I am stuck var items = _Db.Items.ThatAreIn(idsToValidate).ToList(); foreach(var item in items) item.Validated = DateTime.Now; _Db.SubmitChanges(); } // Disposes of DataContext } Or: public void DeleteItems(IList<int> idsToDelete) { using(_Db.NewSession()) // Instatiates new DataContext { // ThatAreIn <- this is where I am stuck var items = _Db.Items.ThatAreIn(idsToValidate); _Db.Items.DeleteAllOnSubmit(items); _Db.SubmitChanges(); } // Disposes of DataContext } Can I get this done in one trip to the database? If so, how? Is it possible to send all those ints to the database as a list of parameters and is that more efficient than doing a foreach over the list to select each item one at a time?

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  • C# XElement: Node Formatting with HTML

    - by Arnej65
    I'm extracting XML node from an XElement. When I use XElement.Value it strips any HTML that may be in the node. I know that if I do XElement.ToString() I can keep the HTML, but it also gives me the node tags. Is there any way to extract the content of a Node as is without the HTML being stripped out? Cheers.

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  • Fixing up an entity framework query

    - by vdh_ant
    My table structure is as follows: Person 1-M PesonAddress Person 1-M PesonPhone Person 1-M PesonEmail Person 1-M Contract Contract M-M Program Contract M-1 Organization At the end of this query I need a populated object graph where each person has their: PesonAddress's PesonPhone's PesonEmail's PesonPhone's Contract's - and this has its respective Program's Now I had the following query and I thought that it was working great, but it has a couple of problems: from people in ctx.People.Include("PersonAddress") .Include("PersonLandline") .Include("PersonMobile") .Include("PersonEmail") .Include("Contract") .Include("Contract.Program") where people.Contract.Any( contract => (param.OrganizationId == contract.OrganizationId) && contract.Program.Any( contractProgram => (param.ProgramId == contractProgram.ProgramId))) select people; The problem is that it filters the person to the criteria but not the Contracts or the Contract's Programs. It brings back all Contracts that each person has not just the ones that have an OrganizationId of x and the same goes for each of those Contract's Programs respectively. What I want is only the people that have at least one contract with an OrgId of x with and where that contract has a Program with the Id of y... and for the object graph that is returned to have only the contracts that match and programs within that contract that match. I kinda understand why its not working, but I don't know how to change it so it is working... This is my attempt thus far: from people in ctx.People.Include("PersonAddress") .Include("PersonLandline") .Include("PersonMobile") .Include("PersonEmail") .Include("Contract") .Include("Contract.Program") let currentContracts = from contract in people.Contract where (param.OrganizationId == contract.OrganizationId) select contract let currentContractPrograms = from contractProgram in currentContracts let temp = from x in contractProgram.Program where (param.ProgramId == contractProgram.ProgramId) select x where temp.Any() select temp where currentContracts.Any() && currentContractPrograms.Any() select new Person { PersonId = people.PersonId, FirstName = people.FirstName, ..., ...., MiddleName = people.MiddleName, Surname = people.Surname, ..., ...., Gender = people.Gender, DateOfBirth = people.DateOfBirth, ..., ...., Contract = currentContracts, ... }; //This doesn't work But this has several problems (where the Person type is an EF object): I am left to do the mapping by myself, which in this case there is quite a lot to map When ever I try to map a list to a property (i.e. Scholarship = currentScholarships) it says I can't because IEnumerable is trying to be cast to EntityCollection Include doesn't work Hence how do I get this to work. Keeping in mind that I am trying to do this as a compiled query so I think that means anonymous types are out.

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  • LINQtoSQL Custom Constructor off Partial Class?

    - by sah302
    Hi all, I read this question here: http://stackoverflow.com/questions/82409/is-there-a-way-to-override-the-empty-constructor-in-a-class-generated-by-linqtosq Typically my constructor would look like: public User(String username, String password, String email, DateTime birthday, Char gender) { this.Id = Guid.NewGuid(); this.DateCreated = this.DateModified = DateTime.Now; this.Username = username; this.Password = password; this.Email = email; this.Birthday = birthday; this.Gender = gender; } However, as read in that question, you want to use partial method OnCreated() instead to assign values and not overwrite the default constructor. Okay so I got this : partial void OnCreated() { this.Id = Guid.NewGuid(); this.DateCreated = this.DateModified = DateTime.Now; this.Username = username; this.Password = password; this.Email = email; this.Birthday = birthday; this.Gender = gender; } However, this gives me two errors: Partial Methods must be declared private. Partial Methods must have empty method bodies. Alright I change it to Private Sub OnCreated() to remove both of those errors. However I am still stuck with...how can I pass it values as I would with a normal custom constructor? Also I am doing this in VB (converted it since I know most know/prefer C#), so would that have an affect on this?

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  • mvc fill dropdownlist

    - by user276640
    i use this code to fill dropdownlist ViewData["projectType"] = new SelectList(_dataManager.Project.ProjectTypeList(), "Id", "Name"); but what i must do if i want to use not one table column but two or more columns? for example ViewData["projectType"] = new SelectList(_dataManager.Project.ProjectTypeList(), "Id", "Name1"+"Name2");

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  • Using Linq2Sql to insert data into multiple tables using an auto incremented primary key

    - by Thomas
    I have a Customer table with a Primary key (int auto increment) and an Address table with a foreign key to the Customer table. I am trying to insert both rows into the database in one nice transaction. using (DatabaseDataContext db = new DatabaseDataContext()) { Customer newCustomer = new Customer() { Email = customer.Email }; Address b = new Address() { CustomerID = newCustomer.CustomerID, Address1 = billingAddress.Address1 }; db.Customers.InsertOnSubmit(newCustomer); db.Addresses.InsertOnSubmit(b); db.SubmitChanges(); } When I run this I was hoping that the Customer and Address table automatically had the correct keys in the database since the context knows this is an auto incremented key and will do two inserts with the right key in both tables. The only way I can get this to work would be to do SubmitChanges() on the Customer object first then create the address and do SubmitChanges() on that as well. This would create two roundtrips to the database and I would like to see if I can do this in one transaction. Is it possible? Thanks

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  • c#: Clean way to fit a collection into a multidimensional array?

    - by Rosarch
    I have an ICollection<MapNode>. Each MapNode has a Position attribute, which is a Point. I want to sort these points first by Y value, then by X value, and put them in a multidimensional array (MapNode[,]). The collection would look something like this: (30, 20) (20, 20) (20, 30) (30, 10) (30, 30) (20, 10) And the final product: (20, 10) (20, 20) (20, 30) (30, 10) (30, 20) (30, 30) Here is the code I have come up with to do it. Is this hideously unreadable? I feel like it's more hacky than it needs to be. private Map createWorldPathNodes() { ICollection<MapNode> points = new HashSet<MapNode>(); Rectangle worldBounds = WorldQueryUtils.WorldBounds(); for (float x = worldBounds.Left; x < worldBounds.Right; x += PATH_NODE_CHUNK_SIZE) { for (float y = worldBounds.Y; y > worldBounds.Height; y -= PATH_NODE_CHUNK_SIZE) { // default is that everywhere is navigable; // a different function is responsible for determining the real value points.Add(new MapNode(true, new Point((int)x, (int)y))); } } int distinctXValues = points.Select(node => node.Position.X).Distinct().Count(); int distinctYValues = points.Select(node => node.Position.Y).Distinct().Count(); IList<MapNode[]> mapNodeRowsToAdd = new List<MapNode[]>(); while (points.Count > 0) // every iteration will take a row out of points { // get all the nodes with the greatest Y value currently in the collection int currentMaxY = points.Select(node => node.Position.Y).Max(); ICollection<MapNode> ythRow = points.Where(node => node.Position.Y == currentMaxY).ToList(); // remove these nodes from the pool we're picking from points = points.Where(node => ! ythRow.Contains(node)).ToList(); // ToList() is just so it is still a collection // put the nodes with max y value in the array, sorting by X value mapNodeRowsToAdd.Add(ythRow.OrderByDescending(node => node.Position.X).ToArray()); } MapNode[,] mapNodes = new MapNode[distinctXValues, distinctYValues]; int xValuesAdded = 0; int yValuesAdded = 0; foreach (MapNode[] mapNodeRow in mapNodeRowsToAdd) { xValuesAdded = 0; foreach (MapNode node in mapNodeRow) { // [y, x] may seem backwards, but mapNodes[y] == the yth row mapNodes[yValuesAdded, xValuesAdded] = node; xValuesAdded++; } yValuesAdded++; } return pathNodes; } The above function seems to work pretty well, but it hasn't been subjected to bulletproof testing yet.

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  • XDocument holding onto Memory?

    - by Jon
    I have an appplication that does a XDocument.Load from a 20mb file and then gets passed to a form to view its contents: openFileDialog1.FileName = ""; if (openFileDialog1.ShowDialog() == DialogResult.OK) { AuditFile = XDocument.Load(openFileDialog1.FileName); fmAuditLogViewer AuditViewer = new fmAuditLogViewer(); AuditViewer.ReportDocument = AuditFile; AuditViewer.Init(); AuditViewer.ShowDialog(); AuditViewer.Dispose(); AuditFile.RemoveNodes(); AuditFile = null; } In Task Manager I can see the memory being used by my application shoot up when I open this file. When I have finished viewing this file in my application I call : myXDocument.RemoveNodes(); myXDocument = null; However the memory use in Task Manager is still pretty high against my app. Is the XDocument still being held in memory and can I decrease the memory usage by my app?

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  • GetRolesForUser tries to get Roles on old username?

    - by Xaisoft
    I have a section on a page where a user can change their username. This is basically the code for that: user.UserName = txtNewUserName.Text; user.Save(); user is a class in my dbml and Save calls SubmitChanges on the data context. The name is changed in the database, so when it calls the following method, it fails because it is trying to get the user with the old username instead of the one that is in the database now. public override string[] GetRolesForUser(string username) { return dc.Users.Where(u => u.UserName== username) .SingleOrDefault().Roles .Select(r => r.RoleName).ToArray<string>(); }

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  • Can't 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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  • ASP.NET GridView Sort?

    - by Curtis White
    I'm performing a query with a sort in the Selecting event of the LinqDataSource. I'm then casting my query to a list and assigning it to the result. I'm using this data source in an ASP.NET gridview. I can see the list is sorted but when the ASP.NET gridview does not seem to be respecting the sort order. How can I get the gridview to respect my default sort order?

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  • Is an IQueryable a query or just an object which can be queried?

    - by Albic
    I'm kinda confused what the IQueryable interface actually represents. The MSDN documentation for IQueryable says: "Provides functionality to evaluate queries against a specific data source." The documentation for IQueryProvider says: "Defines methods to create and execute queries that are described by an IQueryable object." The name and the documentation summary suggest that it is an object/data store which can be queried. The second quote and the fact the ObjectQuery class from the Entity Framework implements IQueryable suggest it is a query which can be executed. Did I misunderstood something or is it really kinda fuzzy?

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  • Why should I use Entity Framework over Linq2SQL ...

    - by Refracted Paladin
    To be clear, I am not asking for a side by side comparision which has already been asked Ad Nauseum here on SO. I am also Not asking if Linq2Sql is dead as I don't care. What I am asking is this.... I am building internal apps only for a non-profit organization. I am the only developer on staff. We ALWAYS use SQL Server as our Database backend. I design and build the Databases as well. I have used L2S successfully a couple of times already. Taking all this into consideration can someone offer me a compelling reason to use EF instead of L2S? I was at Code Camp this weekend and after an hour long demonstration on EF, all of which I could have done in L2S, I asked this same question. The speakers answer was, "L2S is dead..." Very well then! NOT! (see here) I understand EF is what MS WANTS us to use in the future(see here) and that it offers many more customization options. What I can't figure out is if any of that should, or does, matter for me in this environment. One particular issue we have here is that I inherited the Core App which was built on 4 different SQL Data bases. L2S has great difficulty with this but when I asked the aforementioned speaker if EF would help me in this regard he said "No!"

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  • Is there an easy way to compare if 2 XDocuments are equal ignoring element/attribute order?

    - by Davy8
    Unit testing my serialization code I found one failed because I had attributes listed in a different order (I'm just comparing the XDocument.ToString() values) and while I could fix that, it really doesn't matter to me in what order the elements or attributes appear as long as they're all there with the right name at the right level of hierarchy. I could probably write a method do this, but I'm wondering if there's an easy built in way I'm not aware of.

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  • Linq2XML: Get the count of elements where candidate has won2

    - by user287798
    I had an XML Document in the format below <Pronvice_Data> <Pronvice>PronviceA</Pronvice> <Registered_Voters>115852</Registered_Voters> <Sam_Kea>100</Sam_Kea> <Jeje>500</Jeje> <John_Doe>400</John_Doe> </Pronvice_Data> <Pronvice_Data> <Pronvice>PronviceA</Pronvice> <Registered_Voters>25852</Registered_Voters> <Sam_Kea>200</Sam_Kea> <Jeje>100</Jeje> <John_Doe>300</John_Doe> </Pronvice_Data> <Pronvice_Data> <Pronvice>PronviceC</Pronvice> <Registered_Voters>317684</Registered_Voters> <Sam_Kea>1000</Sam_Kea> <Jeje>1200</Jeje> <John_Doe>190</John_Doe> </Pronvice_Data> As suggested by help here,I used the code below to give me this format below C# Code: void Main() { XDocument xmlVectors2 = XDocument.Load(@"C:\\Province_Data.xml"); var elemList= from elem in xmlVectors2.Descendants("Province_Data") where elem.Elements().Count() > 1 select elem; foreach(XElement element in elemList) { XElement elem1= new XElement("Candidates", new XElement(element.Element("Sam_Kea").Name), new XElement(element.Element("Jeje").Name), new XElement(element.Element("John_Doe").Name) ); XElement elem2 = new XElement("Provinces", new XAttribute("Province", (string)element.Element("Province").Value), new XAttribute("Registered_Voters",element.Element("Registered_Voters").Value), new XElement ("Candidate", new XAttribute("Name",element.Element("Sam_Kea").Name), new XAttribute("Votes",element.Element("Sam_Kea").Value) ), new XElement ("Candidate", new XAttribute("Name",element.Element("Jeje").Name), new XAttribute("Votes",element.Element("Jeje").Value) ), new XElement ("Candidate", new XAttribute("Name",element.Element("John_Doe").Name), new XAttribute("Votes",element.Element("John_Doe").Value) )); } } New Format: <root> <Candidates> <Sam_Kea/> <Jeje/> <John_Doe/> </Candidates> <Provinces> <Province name='ProvinceA' Registered_Voters='115852'> <Candidate name='Sam_Kea' votes='100'/> <Candidate name='Jeje' votes='500'/> <Candidate name='John_Doe' votes='400'/> </Province> <Province name='ProvinceB' Registered_Voters='25852'> <Candidate name='Sam_Kea' votes='200'/> <Candidate name='Jeje' votes='100'/> <Candidate name='John_Doe' votes='300'/> </Province> <Province name='ProvinceC' Registered_Voters='317684'> <Candidate name='Sam_Kea' votes='1000'/> <Candidate name='Jeje' votes='1200'/> <Candidate name='John_Doe' votes='190'/> </Province> </Provinces> </root> How can i use the "foreach" in in my code to get the result in this link. http://stackoverflow.com/questions/2396203/get-the-count-of-elements-where-candidate-has-won

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  • Can I serialize an object if I didn't write the class used to instantiate that object?

    - by Richard77
    Hello, I've a simple class [Serializable] public class MyClass { public String FirstName { get; set: } public String LastName { get; set: } //Bellow is what I would like to do //But, it's not working //I get an exception ContactDataContext db = new ContactDataContext(); public void Save() { Contact contact = new Contact(); contact.FirstName = FirstName; contact.LastName = LastName; db.Contacts.InsertOnSubmit(contact); db.SubmitChanges(); } } I wanted to attach a Save method to the class so that I could call it on each object. When I introduced the above statement which contains ContactDataContext, I got the following error "In assembly ... PublicKeyToken=null' is not marked as serializable" It's clear that the DataContext class is generated by the framework (). I checked and did not see where that class was marked serialize. What can I do to overcome that? What's the rule when I'm not the author of a class? Just go ahead and mark the DataContext class as serializable, and pretend that everything will work? Thanks for helping

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  • C# Expression Tree Simple Arithmetic

    - by Richard Adnams
    Hello, I've been trying to figure out how to achieve some simple maths using the Expression class. What I'm trying to do is this (1 + 10 * 15) When I try to do this via Expression.Add and Expression.Constant but the result I get is this ((1 + 10) * 15) Which is not right as it evaluates the 1 + 10 first instead of 10 * 15. Is there a way to combine Expression.Add/Multiply etc.. without it creating the brackets? I assume there is but I just can't find where or how! The test code I have is this var v1 = Expression.Constant(1, typeof(int)); var v2 = Expression.Constant(10, typeof(int)); var v3 = Expression.Constant(15, typeof(int)); var a1 = Expression.Add(v1, v2); var m2 = Expression.Multiply(a1, v3); Thanks for your time, Richard.

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