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  • Entity framework with Linq to Entities performance

    - by mare
    If I have a static method like this public static string GetTicClassificationTitle(string classI, string classII, string classIII) { using (TicDatabaseEntities ticdb = new TicDatabaseEntities()) { var result = from classes in ticdb.Classifications where classes.ClassI == classI where classes.ClassII == classII where classes.ClassIII == classIII select classes.Description; return result.FirstOrDefault(); } } and use this method in various places in foreach loops or just plain calling it numerous times, does it create and open new connection every time? If so, how can I tackle this? Should I cache the results somewhere, like in this case, I would cache the entire Classifications table in Memory Cache? And then do queries vs this cached object? Or should I make TicDatabaseEntities variable static and initialize it at class level? Should my class be static if it contains only static methods? Because right now it is not.. Also I've noticed that if I return result.First() instead of FirstOrDefault() and the query does not find a match, it will issue an exception (with FirstOrDefault() there is no exception, it returns null). Thank you for clarification.

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

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

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  • how to get particular column distinct in linq to sql

    - by kart
    Hi All, Am having columns as category and songs in my table for each category there are almost 10 songs and in total there are 7 category such that which was tabled as category1 songCategory1a category1 songCategory1b category1 songCategory1c --- category2 songCategory2a category2 songCategory2b category2 songCategory2c --- category3 songCategory3a category3 songCategory3b category3 songCategory3c --- like that there is table in that i want to get the result as category1 category2 category3 category4 kindly any one help me , i tried (from s in _context.db_songs select new { s.Song_Name, s.Song_Category }).Distinct().ToList(); but it didnt work its resulting as such.

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  • Linq DBML multiple sql servers

    - by Hurricanepkt
    I have an archive system that had to be on two sql databases for simplicity one is Archive2009 and the other Archive2010 they are both on the same sql server and instance and have identical structures however I have a page that needs to view the old one and the new one (I can make two seperate pages) How best would I go about doing this? Dynamically changing the connection string etc?

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  • LINQ parent child relation

    - by Shane Km
    I'm working on the BLOG functionality in MVC. I need to be able to create 'blog comments'. So each comment may have a parent comment etc. Given table "Comments": CommentId - int - identity autoincrement PostId - int ParentId - int Comment - string Is there a way to get a list of comments for a given article ordered by CreateDate and ParentId? Or maybe there is a better table design you may suggest. What is the best design when inserting Post comments like this? I'm using Entity framework. thanks

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  • Linq to xml : can't load all elements

    - by aleo
    hello i'm trying to load some elements from a xml file. but it XDocument.Load seems not treating xml file properly in this case, the method returns the content of the xml file as one node. here is my xml content: <processes> <process>winamp</process> <process>Acrobat</process> <process>WinRAR</process> </processes> and the code that reads the file: XDocument loaded = XDocument.Load("/process_list.xml"); var x = from a in loaded.Descendants("processes") select a.Element("process"); foreach (var t in x) { Console.WritleLine(t.Value.ToString()); } thank you

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  • LINQ to SQL left outer joins

    - by César
    Is this query equivalent to a LEFT OUTER join? var rows = from a in query join s in context.ViewSiteinAdvise on a.Id equals s.SiteInAdviseId where a.Order == s.Order select new {....}; I tried this but it did not result from s in ViewSiteinAdvise join q in query on s.SiteInAdviseId equals q.Id into sa from a in sa.DefaultIfEmpty() where s.Order == a.Order select new {s,a} I need all columns from View

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  • Linq To Sql Entity Updated from Trigger

    - by James Helms
    I have a Table called Address. I have a Trigger for insert on that table that does some spacial calculations on the address that determines what neighborhood boundaries it is in. address = new Address { Street = this.Street, City = this.City, State = this.State, ZipCode = this.ZipCode, latitude = this.Latitude, longitude = this.Longitude, YearBuilt = this.YearBuilt, LotSize = this.LotSize, FinishedSize = this.FinishedSize, Bedrooms = this.Bedrooms, Bathrooms = this.Bathrooms, UseCode = this.UseCode, HOA = this.HOA, UpdateDate = DateTime.Now }; db.AddToAddresses(address); db.SaveChanges(); In the database i can clearly see that the Trigger ran and updated the neighborhoodID in the address table for the row. I tried to just reload that record to get the assigned id like this: address = (from a in db.Addresses where a.AddressID == address.AddressID select a).First(); In the debugger i can clearly see that the address.AddressID is correct, entity doesn't update in memory. Is there any work around for this?

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  • LINQ, creating unique collection of a collection

    - by Wish
    I have class Vertex and a class Edge (Edge holds 2 properties - Vertex Source and Vertex Target); Edges and Vertexes are collected into lists Some example: A-->B // edge from vertex A to B B-->C // edge from vertex B to C C-->A // edge from vertex C to A A-->C // edge from vertex A to C -- this is two way edge So I would like to make IDictionary<Edge, bool> which would hold edges (A--B and B--A would be like 1), and bool - if it is two way or no. I need it because when I draw them now, it draws 2 arrows under one another. I would better make 1 arrow. So I'm pretty stuck right here... May anybody help me a bit ?

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  • LINQ - more than or equal to

    - by trnTash
    Part of the code: ...where se.DateFrom >= pDateFrom && se.DateTo <= pDateTo select se... Does not work. There is no any error but the To and From days do not get returned. How do I query "more than or equal to" and "less than or equal to"? Thanks :)

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  • LINQ to SQL: NOTing a prebuilt expression

    - by ck
    I'm building a library of functions for one of my core L2S classes, all of which return a bool to allow checking for certain situations. Example: Expression<Func<Account, bool>> IsSomethingX = a => a.AccountSupplementary != null && a.AccountSupplementary.SomethingXFlag != null && a.AccountSupplementary.SomethingXFlag.Value; Now to query where this is not true, I CAN'T do this: var myAccounts= context.Accounts .Where(!IsSomethingX); // does not compile However, using the syntax from the PredicateBuilder class, I've come up with this: public static IQueryable<T> WhereNot<T>(this IQueryable<T> items, Expression<Func<T, bool>> expr1) { var invokedExpr = Expression.Invoke(expr1, expr1.Parameters.Cast<Expression>()); return items.Where(Expression.Lambda<Func<T, bool>> (Expression.Not(invokedExpr), expr1.Parameters)); } var myAccounts= context.Accounts .WhereNot(IsSomethingX); // does compile which actually produces the correct SQL. Does this look like a good solution, and is there anything I need to be aware of that might cause me problems in future?

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  • Keeping Linq to SQL alive when using ViewModels (ASP.NET MVC)

    - by Kohan
    I have recently started using custom ViewModels (For example, CustomerViewModel) public class CustomerViewModel { public IList<Customer> Customers{ get; set; } public int ProductId{ get; set; } public CustomerViewModel(IList<Customer> customers, int productId) { this.Customers= customers; this.ProductId= productId; } public CustomerViewModel() { } } ... and am now passing them to my view instead of the Entities themselves (for example, var Custs = repository.getAllCusts(id) ) as it seems good practice to do so. The problem i have encountered is that when using ViewModels; by the time it has got to the the view i have lost the ability to lazy load on customers. I do not believe this was the case before using them. Is it possible to retain the ability of Lazy Loading while still using ViewModels? Or do i have to eager load using this method? Thanks, Kohan.

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  • linq to xml return second element

    - by Phil
    Hi Im trying to return to the second element in the xml from flickr. This always returns the first element: ImageUrl = item.Element(ns + "link").Attribute("href").Value, and this errors? ImageUrl = item.Elements(ns + "link")[1].Attribute("href").Value, Thanks

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  • Linq TakeWhile depending on sum (or aggregate) of elements

    - by martinweser
    I have a list of elements and want to takeWhile the sum (or any aggregation of the elements) satisfy a certain condition. The following code does the job, but i am pretty sure this is not an unusual problem for which a proper pattern should exist. var list = new List<int> { 1, 2, 3, 4, 5, 6, 7 }; int tmp = 0; var listWithSum = from x in list let sum = tmp+=x select new {x, sum}; int MAX = 10; var result = from x in listWithSum where x.sum < MAX select x.x; Does somebody know how to solve the task in nicer way, probably combining TakeWhile and Aggregate into one query? Thx

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  • For-Loop and LINQ's deferred execution don't play well together

    - by Tim Schmelter
    The title suggests that i've already an idea what's going on, but i cannot explain it. I've tried to order a List<string[]> dynamically by each "column", beginning with the first and ending with the minimum Length of all arrays. So in this sample it is 2, because the last string[] has only two elements: List<string[]> someValues = new List<string[]>(); someValues.Add(new[] { "c", "3", "b" }); someValues.Add(new[] { "a", "1", "d" }); someValues.Add(new[] { "d", "4", "a" }); someValues.Add(new[] { "b", "2" }); Now i've tried to order all by the first and second column. I could do it statically in this way: someValues = someValues .OrderBy(t => t[0]) .ThenBy(t => t[1]) .ToList(); But if i don't know the number of "columns" i could use this loop(that's what I thought): int minDim = someValues.Min(t => t.GetLength(0)); // 2 IOrderedEnumerable<string[]> orderedValues = someValues.OrderBy(t => t[0]); for (int i = 1; i < minDim; i++) { orderedValues = orderedValues.ThenBy(t => t[i]); } someValues = orderedValues.ToList(); // IndexOutOfRangeException But that doesn't work, it fails with an IndexOutOfRangeException at the last line. The debugger tells me that i is 2 at that time, so the for-loop condition seems to be ignored, i is already == minDim. Why is that so?

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  • Manual Linq to SQL entity framework mapping

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

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  • Linq grouping question

    - by Mike C.
    I have the following objects in a collection: Transaction: Type = "Widget" Date = "3/1/2011" Name = "Foo" Transaction: Type = "Widget" Date = "3/4/2011" Name = "Bar" Transaction: Type = "Gadget" Date = "3/2/2011" Name = "Baz" Transaction: Type = "Gizmo" Date = "3/1/2011" Name = "Who" Transaction: Type = "Gizmo" Date = "3/2/2011" Name = "What" Transaction: Type = "Gizmo" Date = "3/6/2011" Name = "When" I want to end up with the following, grouped by Type. If there are multiple, return only the first one chronologically by date. Transaction: Type = "Widget" Date = "3/1/2011" Name = "Foo" Transaction: Type = "Gadget" Date = "3/2/2011" Name = "Baz" Transaction: Type = "Gizmo" Date = "3/1/2011" Name = "Who"

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  • C# LINQ filtering with nested if statements

    - by Tim Sumrall
    I have a learning project where a data grid is filtered by 3 controls (a checkbox and 2 dropdowns) I'm about to wrap up and move on to another project as it works well but I don't like the complexity of nesting IF statements to capture all the possible combinations of the 3 filters and was wondering if there is a better way. For example: Something that would allow for more filters to be added easily rather than walking through all the nests and adding another level of madness. private void BuildQuery() { EntityQuery<MASTER_DOCKS> query = QDocksContext.GetMASTER_DOCKSQuery(); if (Tonnage.IsChecked.HasValue && Tonnage.IsChecked.Value) { if (null != FilterWaterWay.SelectedValue) { string WaterwaytoFilterBy = FilterWaterWay.SelectedValue.ToString(); if (!string.IsNullOrWhiteSpace(WaterwaytoFilterBy) && WaterwaytoFilterBy != "[Select WaterWay]") { if (null != FilterState.SelectedValue) { string StateToFilterBy = FilterState.SelectedValue.ToString(); if (null != FilterState.SelectedValue && !string.IsNullOrWhiteSpace(StateToFilterBy) && StateToFilterBy != "[Select State]") { if (!string.IsNullOrWhiteSpace(StateToFilterBy) && StateToFilterBy != "[Select State]") { query = query.Where(s => s.WTWY_NAME == WaterwaytoFilterBy && s.STATE == StateToFilterBy && (s.Tons != "0" && s.Tons != "")).OrderBy(s => s.WTWY_NAME); MyQuery.Text = "Tonnage, WW and State"; } } if (StateToFilterBy == "[Select State]") //waterway but no state { query = query.Where(s => s.WTWY_NAME == WaterwaytoFilterBy && (s.Tons != "0" && s.Tons != "")).OrderBy(s => s.WTWY_NAME); MyQuery.Text = "Tonnage, WW No State"; } } } else { if (null != FilterState.SelectedValue) { string StateToFilterBy = FilterState.SelectedValue.ToString(); if (null != FilterState.SelectedValue && !string.IsNullOrWhiteSpace(StateToFilterBy) && StateToFilterBy != "[Select State]") { if (!string.IsNullOrWhiteSpace(StateToFilterBy) && StateToFilterBy != "[Select State]") { query = query.Where(s => s.STATE == StateToFilterBy && (s.Tons != "0" && s.Tons != "")).OrderBy(s => s.WTWY_NAME); MyQuery.Text = "Tonnage State No WW"; } } else { query = query.Where(s => (s.Tons != "0" && s.Tons != "")); MyQuery.Text = "Tonnage No State No WW"; } } } } } else //no tonnage { if (null != FilterWaterWay.SelectedValue) { string WaterwaytoFilterBy = FilterWaterWay.SelectedValue.ToString(); if (!string.IsNullOrWhiteSpace(WaterwaytoFilterBy) && WaterwaytoFilterBy != "[Select WaterWay]") { if (null != FilterState.SelectedValue) { string StateToFilterBy = FilterState.SelectedValue.ToString(); if (null != FilterState.SelectedValue && !string.IsNullOrWhiteSpace(StateToFilterBy) && StateToFilterBy != "[Select State]") { if (!string.IsNullOrWhiteSpace(StateToFilterBy) && StateToFilterBy != "[Select State]") { query = query.Where(s => s.WTWY_NAME == WaterwaytoFilterBy && s.STATE == StateToFilterBy).OrderBy(s => s.WTWY_NAME); MyQuery.Text = "No Tonnage, WW and State"; } } if (StateToFilterBy == "[Select State]") //waterway but no state { query = query.Where(s => s.WTWY_NAME == WaterwaytoFilterBy).OrderBy(s => s.WTWY_NAME); MyQuery.Text = "No Tonnage, WW No State"; } } } else { if (null != FilterState.SelectedValue) { string StateToFilterBy = FilterState.SelectedValue.ToString(); if (null != FilterState.SelectedValue && !string.IsNullOrWhiteSpace(StateToFilterBy) && StateToFilterBy != "[Select State]") { if (!string.IsNullOrWhiteSpace(StateToFilterBy) && StateToFilterBy != "[Select State]") { query = query.Where(s => s.STATE == StateToFilterBy).OrderBy(s => s.WTWY_NAME); MyQuery.Text = "No Tonnage State No WW"; } } else { LoadAllData(); MyQuery.Text = "No Tonnage No State No WW"; } } } } } LoadOperation<MASTER_DOCKS> loadOp = this.QDocksContext.Load(query); DocksGrid.ItemsSource = loadOp.Entities; }

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  • Linq to Sql query reuse

    - by UserControl
    Let's say we have a view V1 and V2 that is declared like: create view V2 as select V1.*, V2.C1, V2.C2, V2.C3 from V1 join V2 on V1.Key = V2.Key where bla-bla So V2 narrows down the result set of V1 and adds some joins. And there is a retrieval routine in C# IEnumerable<V1> GetData(MyFilter filter, MySortOrder order) {} I want to reuse with V2. Is it possible without performing joins in L2S rather than in database? Should i manually create a base class in the database context or something?

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  • Forcing LINQ to SQL to make one single call for all child rows

    - by zaph0d
    Let say I have a method (example taken from another post): public IQueryable<CityBlock> GetCityBlocks(){ var results = from o in db.city_blocks let buildings = GetBuildingsOnBlock(o.block_id) //returns Iqueryable select new CityBlock { BuildingsOnBlock = buildings, BlockOwner = o.block_owner }; return results; } In the calling method I add Skip() and Take() methods plus some filtering and then do a ToList(). The trouble is that I am getting dozens of database calls - one for all the city blocks and then a separate one for each building. Is there a way that I can refactor this code to just make two calls: one for the city blocks and one for all the buildings

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  • Is Linq Faster, Slower or the same?

    - by Vaccano
    Is this: Box boxToFind = AllBoxes.Where(box => box.BoxNumber == boxToMatchTo.BagNumber); Faster or slower than this: Box boxToFind ; foreach (Box box in AllBoxes) { if (box.BoxNumber == boxToMatchTo.BoxNumber) { boxToFind = box; } } Both give me the result I am looking for (boxToFind). This is going to run on a mobile device that I need to be performance conscientious of.

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  • Storing records in a dropdownlist from DB without using LINQ Data source

    - by user1318369
    I have a website for dance academy where Users can register and add/drop dance classes. In the web page to drop a particular dance, for a particular user, the dropdown displays her registered dances. Now I want to delete one of the dances from the list. So i'll remove the row from the table and also from the dropdownlist. The problem is that everytime the item with the lowest ID (index) is getting deleted, no matter which one the user selects. I think I am storing the DataTextField and DataValueField for the dropdown incorrectly. Can someone please help me out? The code is: private void PopulateDanceDropDown() { var registereddanceList = from dd in context.DANCER_AND_DANCE where dd.UserId == dancerId select new { Text = dd.DanceName, Value = dd.DanceId }; dances.DataSource = registereddanceList; dances.DataTextField = "Text"; dances.DataValueField = "Value"; dances.DataBind(); } protected void dropthedance(object o, EventArgs e) { String strDataValueField = dances.SelectedItem.Value; int danceIDFromDropDown = Convert.ToInt32(strDataValueField); var dancer_dance = from dd in context.DANCER_AND_DANCE where dd.DanceId == danceIDFromDropDown select dd; foreach (var dndd in dancer_dance) { context.DANCER_AND_DANCE.DeleteOnSubmit(dndd); } try { context.SubmitChanges(); } catch (Exception ex) { Console.WriteLine(ex); } PopulateDanceDropDown(); }

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