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  • VB .Net LINQ query to determine whether more than one element has the same value for a property?

    - by Alex Hope O'Connor
    I am trying to write a LINQ query which will return true if there are multiple objects which have a property with the same value. Here is what I have come up with so far: Formatters.Where(Function(f As DataModel.Formatter) _ Formatters.Select(Function(f2 As DataModel.Formatter) f2.Name.ToLower()).Contains(f.Name.ToLower())).Count > 1 However the above always returns true as long as their are more then 1 elements in the list, can someone please give me a hand with this? Thanks, Alex.

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  • What is the most elegant way to implement a business rule relating to a child collection in LINQ?

    - by AaronSieb
    I have two tables in my database: Wiki WikiId ... WikiUser WikiUserId (PK) WikiId UserId IsOwner ... These tables have a one (Wiki) to Many (WikiUser) relationship. How would I implement the following business rule in my LINQ entity classes: "A Wiki must have exactly one owner?" I've tried updating the tables as follows: Wiki WikiId (PK) OwnerId (FK to WikiUser) ... WikiUser WikiUserId (PK) WikiId UserId ... This enforces the constraint, but if I remove the owner's WikiUser record from the Wiki's WikiUser collection, I recieve an ugly SqlException. This seems like it would be difficult to catch and handle in the UI. Is there a way to perform this check before the SqlException is generated? A better way to structure my database? A way to catch and translate the SqlException to something more useful? Edit: I would prefer to keep the validation rules within the LINQ entity classes if possible. Edit 2: Some more details about my specific situation. In my application, the user should be able to remove users from the Wiki. They should be able to remove any user, except the user who is currently flagged as the "owner" of the Wiki (a Wiki must have exactly one owner at all times). In my control logic, I'd like to use something like this: wiki.WikiUsers.Remove(wikiUser); mRepository.Save(); And have any broken rules transferred to the UI layer. What I DON'T want to have to do is this: if(wikiUser.WikiUserId != wiki.OwnerId) { wiki.WikiUsers.Remove(wikiUser); mRepository.Save(); } else { //Handle errors. } I also don't particularly want to move the code to my repository (because there is nothing to indicate not to use the native Remove functions), so I also DON'T want code like this: mRepository.RemoveWikiUser(wiki, wikiUser) mRepository.Save(); This WOULD be acceptable: try { wiki.WikiUsers.Remove(wikiUser); mRepository.Save(); } catch(ValidationException ve) { //Display ve.Message } But this catches too many errors: try { wiki.WikiUsers.Remove(wikiUser); mRepository.Save(); } catch(SqlException se) { //Display se.Message } I would also PREFER NOT to explicitly call a business rule check (although it may become necessary): wiki.WIkiUsers.Remove(wikiUser); if(wiki.CheckRules()) { mRepository.Save(); } else { //Display broken rules }

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  • How can I iterate over a collection of objects returned by a LINQ-to-XML query?

    - by billmaya
    I've got this XML: <BillingLog> <BillingItem> <date-and-time>2003-11-04</date-and-time> <application-name>Billing Service</application-name> <severity>Warning</severity> <process-id>123</process-id> <description>Timed out on a connection</description> <detail>Timed out after three retries.</detail> </BillingItem> <BillingItem> <date-and-time>2010-05-15</date-and-time> <application-name>Callback Service</application-name> <severity>Error</severity> <process-id>456</process-id> <description>Unable to process callback</description> <detail>Reconciliation timed out after two retries.</detail> </BillingItem> </BillingLog> That I want to project using LINQ-to-XML into a collection of BillingItem objects contained in a single BillingLog object. public class BillingLog { public IEnumerable<BillingItem> items { get; set; } } public class BillingItem { public string Date { get; set; } public string ApplicationName { get; set; } public string Severity { get; set; } public int ProcessId { get; set; } public string Description { get; set; } public string Detail { get; set;} } This is the LINQ query that I'm using to project the XML (which is contained in the string variable source). XDocument xdoc = XDocument.Parse(source); var log = from i in xdoc.Elements("BillingLog") select new BillingLog { items = from j in i.Descendants("BillingItem") select new BillingItem { Date = (string)j.Element("date-and-time"), ApplicationName = (string)j.Element("application-name"), Severity = (string)j.Element("severity"), ProcessId = (int)j.Element("process-id"), Description = (string)j.Element("description"), Detail = (string)j.Element("detail") } }; When I try and iterate over the objects in log using foreach. foreach (BillingItem item in log) { Console.WriteLine ("{0} | {1} | {2} | {3} | {4} | {5}", item.Date, item.ApplicationName, item.Severity, item.ProcessId.ToString(), item.Description, item.Detail); } I get the following error message from LINQPad. Cannot convert type 'UserQuery.BillingLog' to 'UserQuery.BillingItem' Thanks in advance.

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  • Get the count of items in a GroupBy Linq-to-sql Query?

    - by Curtis White
    I have a groupby that I groups all elements. I can see the items are there in LinqPad but can't find a way to get the count. Here is what I have so far: SurveyResponses.Where( q = q.QuestionId == 4).GroupBy(q = q.AnswerNumeric).Where( g = g.Key == 1) In Linq Pad I can see there are 4 items in this query. If I do Count it returns 1. I've tried, ToList().Count, Select(x = x).Count, etc.

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  • LINQ how to add an order by to this statement?

    - by JL
    I have the following LINQ that I would like to also order by file creation date, how is this done? taskFiles = taskDirectory.GetFiles(Id + "*.xml") .Where(fi => !fi.Name.EndsWith("_update.xml", StringComparison.CurrentCultureIgnoreCase)) .ToArray();

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  • LINQ Group By to project into a non-anonymous type?

    - by vikp
    Hi, I have the following LINQ example: var colorDistribution = from product in ctx.Products group product by product.Color into productColors select new { Color = productColors.Key, Count = productColors.Count() }; All this works and makes perfect sense. What I'm trying to achieve is to group by into a strong type instead of anonymous type. For example I have a ProductColour class and I would like to Group into a List<ProductColour> Is this possible? Thank you

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  • How to wrap LINQ to SQL queries in stored proc?

    - by Satish
    LINQ to SQL internally generates SQL queries and fire on the database after submitting changes. Is there any way we can wrap all these queries in some stored procedure and execute this store proc everytime when anything gets inserted or updated in the database. Problem is only stored procedures are allowed to carry any insert or update or delete operations, direct queries are restricted for security purpose.

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  • How to use LINQ to query list of strings that do not contain substring entries from another list

    - by p.campbell
    string candidates = new string[] { "Luke_jedi", "Force_unknown", "Vader_jedi" , "Emperor_human", "r2d2_robot" }; string[] disregard = new string[] {"_robot", "_jedi"}; //find those that aren't jedi or robots. var nonJedi = candidates.Where(c=> c.??? //likely using EndsWith() and Any() ); How would you implement this solution using LINQ to find all those that do not end with any of the disregards items?

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  • How to use Linq To Sql to get Users who has less than 2 photos?

    - by Mike108
    The scenario is I want to get the users who has less than 2 photos. There are two table: [Users] (UserId, UserName) [UserPhotos] (PhotoId, PhotoName, UserId) UserId is a Foreign Key but I do not want to use association like user.Photos. A user may have none photo in the [UserPhotos] table. How to use Linq To Sql to get List<User> who has less than 2 photos?

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  • How do I check if a Linq to SQL entity has grandchildren?

    - by EdenMachine
    How can I find out if a Linq to SQL entity has grandchildren or not? Pseudo-code below: Return From p In dc.Processes Where p.Signers.Count > 0 and p.Signers.Signatures.Count > 0 Obviously I can't run the code above but I need to make sure that all the returning Processes have at least one Signer and that all of those Signers have at least one Signature. TIA!

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  • How do I use "Into" LINQ expression in VB.NET?

    - by SLC
    I'm converting from C# this LINQ expression. However, it does not seem to work. C# return (from w in fishSticks group w by w.FishQty into g orderby g.Key descending select g).First().First(); VB Return (From w In fishSticks Group w By w.FishQty Into g() Order By g.Key Descending Select g).First().First() Visual Studio turns g into g() itself and then gives me this error: Definition of method 'g' is not accessible in this context. Any ideas?

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  • How do I perform this XPath query with Linq?

    - by John Hansen
    In the following code I am using XPath to find all of the matching nodes using XPath, and appending the values to a StringBuilder. StringBuilder sb = new StringBuilder(); foreach (XmlNode node in this.Data.SelectNodes("ID/item[@id=200]/DAT[1]/line[position()>1]/data[1]/text()")) { sb.Append(node.Value); } return sb.ToString(); How do I do the same thing, except using Linq to XML instead? Assume that in the new version, this.Data is an XElement object.

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  • Is it OK to try to use Plinq in all Linq queries?

    - by Tony_Henrich
    I read that PLinq will automatically use non parallel Linq if it finds PLinq to be more expensive. So I figured then why not use PLinq for everything (when possible) and let the runtime decide which one to use. The apps will be deployed to multicore servers and I am OK to develop a little more code to deal with parallelism. What are the pitfalls of using plinq as a default?

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  • Linq to SQL: how get row security between write access??

    - by Francisco
    I would like to allow two threads to write in a table at the same time (I know the problem of updating the same row, but this would be a story apart). I need that in behalf of speed up the operations in my aplication (one thread could write in row X while another could do the same in row X+n instead of waiting the first to finalize). So, can I block rows instead of tables with Linq to SQL? Thanks.

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