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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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• 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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• 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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• When does logic belong in the Business Object/Entity, and when does it belong in a Service?

  - by Casey

  In trying to understand Domain Driven Design I keep returning to a question that I can't seem to definitively answer. How do you determine what logic belongs to a Domain entity, and what logic belongs to a Domain Service? Example: We have an Order class for an online store. This class is an entity and an aggregate root (it contains OrderItems). Public Class Order:IOrder { Private List<IOrderItem> OrderItems Public Order(List<IOrderItem>) { OrderItems = List<IOrderItem> } Public Decimal CalculateTotalItemWeight() //This logic seems to belong in the entity. { Decimal TotalWeight = 0 foreach(IOrderItem OrderItem in OrderItems) { TotalWeight += OrderItem.Weight } return TotalWeight } } I think most people would agree that CalculateTotalItemWeight belongs on the entity. However, at some point we have to ship this order to the customer. To accomplish this we need to do two things: 1) Determine the postage rate necessary to ship this order. 2) Print a shipping label after determining the postage rate. Both of these actions will require dependencies that are outside the Order entity, such as an external webservice to retrieve postage rates. How should we accomplish these two things? I see a few options: 1) Code the logic directly in the domain entity, like CalculateTotalItemWeight. We then call: Order.GetPostageRate Order.PrintLabel 2) Put the logic in a service that accepts IOrder. We then call: PostageService.GetPostageRate(Order) PrintService.PrintLabel(Order) 3) Create a class for each action that operates on an Order, and pass an instance of that class to the Order through Constructor Injection (this is a variation of option 1 but allows reuse of the RateRetriever and LabelPrinter classes): Public Class Order:IOrder { Private List<IOrderItem> OrderItems Private RateRetriever _Retriever Private LabelPrinter _Printer Public Order(List<IOrderItem>, RateRetriever Retriever, LabelPrinter Printer) { OrderItems = List<IOrderItem> _Retriever = Retriever _Printer = Printer } Public Decimal GetPostageRate { _Retriever.GetPostageRate(this) } Public void PrintLabel { _Printer.PrintLabel(this) } } Which one of these methods do you choose for this logic, if any? What is the reasoning behind your choice? Most importantly, is there a set of guidelines that led you to your choice?

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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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• 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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• 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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• Equivalent lambda syntax for linq query

  - by ilias

  Hi, I am having a mind-freeze here, but I cant seem to find the equivalent lambda syntax for - string[] a = {"a","b","c"}; string[] b = {"1","2","3"}; var x = from a1 in a from b1 in b select new{a1, b1};

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• C# Linq - Cannot implicitly convert IEnumerable<string> to List<string>

  - by JL

  I have a List defined like this : public List<string> AttachmentURLS; I am adding items to the list like this: instruction.AttachmentURLS = curItem.Attributes["ows_Attachments"].Value.Split(';').ToList().Where(Attachment => !String.IsNullOrEmpty(Attachment)); But I am getting this error: Cannot implicitly convert IEnumerable to List What am I doing wrong?

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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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• How to integrate "basic" website into Zend Framework

  - by Joel

  Hi guys, I have a website that has around 10 pages. Only one of those pages uses Zend (to integrate with Google gData). Right now, it's just all coded into that one page, but I'm wanting to learn how to use Zend Framework. How do you handle basic-relatively static php pages within Zend Framework? Do you just stick the whole individual pages into their own respective views and then have to common stuff in the layout, and not worry about a model and controller for those pages? in general, is MVC accepted and appropriate technology for general "web-design" work?

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• VB.NET and linQ: How to delete entries from a dictionary using the value

  - by user350233

  I have a dictionary collection as bleow: mydic.addvalue(key1, val1) mydic.addvalue(key2, val1) mydic.addvalue(key3, val1) mydic.addvalue(key4, val2) mydic.addvalue(key5, val2) From the above dictionary I want to delete all the entries where value == "val1", so that the result would have only following entry: mydic.addvalue(key4, val2) mydic.addvalue(key5, val2) My VB source code is on VS2008 and targeted for 3.5

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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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• How to use the IN operator in linq

  - by Hallaghan

  I'm querying a view and filtering the results with a column named status. I'd like to query it so I can search for rows with different status, by using the IN operator as I'd do in SQL. As so: SELECT * FROM VIEW WHERE Status in ('....', '.....') How can I achieve this?

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• Exploding a range of dates with LINQ

  - by Robert Gowland

  If I have a pair of dates, and I want to generate a list of all the dates between them (inclusive), I can do something like: System.DateTime s = new System.DateTime(2010, 06, 05); System.DateTime e = new System.DateTime(2010, 06, 09); var list = Enumerable.Range(0, (e - s).Days) .Select(value => s.AddDays(value)); What I'm stuck on is that I've got a list of pairs of dates that I want to explode into a list of all the dates between them. Example: {2010-05-06, 2010-05-09}, {2010-05-12, 2010-05-15} should result in {2010-05-06, 2010-05-07, 2010-05-08, 2010-05-09, 2010-05-12, 2010-05-13, 2010-05-14, 2010-05-15} Note the pairs of dates are guaranteed not to overlap each other.

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• Haskell UI framework?

  - by Lance May

  Is there, by chance, and emerging Haskell UI framework for Windows? I recently took up looking over the language, and from what I see, it would be great little "one-off" applications (elaborate scripts). However, without a good UI framework I can't see it getting in under the smoke and mirrors of the more obvious contenders. I've read that there are many frameworks, but none are full-featured. I'm just wondering if this is something that's on the rise, or is it simply too difficult to get enough developers going in the same direction with one?

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• is there a twitter user login framework for gae

  - by zjm1126

  i want to someone login use twitter , so, has a framework that you already make successful doing this , thanks

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• Grabbing Just The Top Entry From A LINQ Query

  - by Soo

  I basically have a lot of poorly designed code to do something that, I'm sure, can be done far more elegantly. What I'm trying to do is grab the last date from a database table. var Result = from a in DB.Table orderby a.Date descending select new {Date = a}; foreach(var Row in Result) { LastDate = Row.Date.Date; break; } Basically, there's a foreach loop that is designed to run only once. Crappy code! What's a "best practice" way to accomplish the same thing?

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• Making linq avoid using in memory filtering where possible

  - by linqmonkey

  Consider the these two LINQ2SQL data retrieval methods. The first creates a 'proper' SQL statement that filters the data, but requires passing the data context into the method. The second has a nicer syntax but loads the entire list of that accounts projects, then does in memory filtering. Is there any way to preserve the syntax of the second method but with the performance advantage of the first? public partial class Account { public IQueryable<Project> GetProjectsByYear(LinqDataContext context, int year) { return context.Projects.Where(p => p.AccountID==this.AccountID && p.Year==year).OrderBy(p => p.ProjectNo) } public IQueryable<Project> GetProjectsByYear(int year) { return this.Projects.Where(p => p.Year==year).OrderBy(p => p.ProjectNo).AsQueryable() } }

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• Linq-to-sql join/where?

  - by Curtis White

  I've the following table structures Users id Types id isBool UsersTypes userid types I want to select all the UserTypes based on id and isBool. I tried this query var q = from usertype in usertypes from type in types where type.isBool == false where userstypes.user == id select usertype; But this did not work as expected. My questions are: Why? Is there any difference in using the join on syntax vs where, where vs where cond1 && cond2? My understanding is query optimizer will optimize. Is there any difference in using where cond1 == var1 && cond2 == var2 with and without the parenthesis? This seems peculiar that it is possible to build this without parenthesis What type of query do I need in this case? I can see that I could do a subquery or use a group but not 100% sure if it is required. An example might be helpful. I'm thinking a subquery may be required in this case.

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• C# LINQ join With Just One Row

  - by Soo

  I'm trying to make a query that grabs a single row from an SQL database and updates it. TableA AId AValue TableB BId AId BValue Ok, so TableA and TableB are linked by AId. I want to select a row in TableB based on AValue using a join. The following query is what I have and only grabs a value from TableB based on AId, I just don't know how to grab a row from TableB using AValue. I know you would need to use a join, but I'm not sure how to accomplish that. var row = DbObject.TableB.Single(x => x.AId == 1) row.BValue = 1; DbObject.SubmitChanges();

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• linq to sql update data

  - by pranay

  can i update my employee record as given in below function or i have to make query of employee collection first and than i update data public int updateEmployee(App3_EMPLOYEE employee) { DBContextDataContext db = new DBContextDataContext(); db.App3_EMPLOYEEs.Attach(employee); db.SubmitChanges(); return employee.PKEY; } or i have to do this public int updateEmployee(App3_EMPLOYEE employee) { DBContextDataContext db = new DBContextDataContext(); App3_EMPLOYEE emp = db.App3_EMPLOYEEs.Single(e => e.PKEY == employee.PKEY); db.App3_EMPLOYEEs.Attach(employee,emp); db.SubmitChanges(); return employee.PKEY; } But i dont want to use second option is there any efficient way to update data

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• Linq Return node level of hierarchical xml

  - by Ryan

  In a treeview you can retrieve the level of an item. I am trying to accomplish the same thing with the given input being an object. The XML data I will use for this example would be something like the following <?xml version="1.0" encoding="utf-8" ?> <Testing> <Numbers> <Number val="1"> <Number val="1.1"> <Number val="1.1.1"> <Number val="1.1.2" /> <Number val="1.1.3" /> <Number val="1.1.4" /> </Number> </Number> <Number val="1.2" /> <Number val="1.3" /> <Number val="1.4" /> </Number> <Number val="2" /> <Number val="3" /> <Number val="4" /> </Numbers> <Numbers> <Number val="5" /> <Number val="6" /> <Number val="7" /> <Number val="8" /> </Numbers> </Testing> This one is kicking my butt!

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• Query decendants in XML to Linq

  - by Gordon

  I have the following xml data: <portfolio> <item> <title>Site</title> <description>Site.com is a </description> <url>http://www.site.com</url> <photos> <photo url="http://www.site.com/site/thumbnail.png" thumbnail="true" description="Main" /> <photo url="http://www.site.com/site/1.png" thumbnail="false" description="Main" /> </photos> </item> </portfolio> In c# I am using the following link query: List list = new List(); XDocument xmlDoc = XDocument.Load(HttpContext.Current.Server.MapPath("~/app_data/portfolio.xml")); list = (from portfolio in xmlDoc.Descendants("item") select new PortfolioItem() { Title = portfolio.Element("title").Value, Description = portfolio.Element("description").Value, Url = portfolio.Element("url").Value }).ToList(); How do I go about querying the photos node? In the PortfolioItem class I have a property: List Photos {get;set;} Any ideas would be greatly appreciated!

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