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  • Why does Linq to Entity Sum return null when the result set is empty?

    - by Hannele
    There are quite a few questions on Stack Overflow about the Linq to Entity / Linq to SQL Sum extension method, about how it returns null when the result set is empty: 1, 2, 3, 4, 5, 6, 7, and many more, as well as a blog post discussing the issue here. I feel it is an inconsistency in the Linq implementation. I am assuming at this point that it is not a bug, but is more or less working as designed. I understand that there are workarounds (for example, casting the field to a nullable type, so you can coalesce with ??), and I also understand that for the underlying SQL, a NULL result is expected for an empty result set. But because the result of the Sum extension for non-nullable types is also non-nullable, why does the Linq to SQL / Linq to Entity Sum behave this way?

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  • How to eager load sibling data using LINQ to SQL?

    - by Scott
    The goal is to issue the fewest queries to SQL Server using LINQ to SQL without using anonymous types. The return type for the method will need to be IList<Child1>. The relationships are as follows: Parent Child1 Child2 Grandchild1 Parent Child1 is a one-to-many relationship Child1 Grandchild1 is a one-to-n relationship (where n is zero to infinity) Parent Child2 is a one-to-n relationship (where n is zero to infinity) I am able to eager load the Parent, Child1 and Grandchild1 data resulting in one query to SQL Server. This query with load options eager loads all of the data, except the sibling data (Child2): DataLoadOptions loadOptions = new DataLoadOptions(); loadOptions.LoadWith<Child1>(o => o.GrandChild1List); loadOptions.LoadWith<Child1>(o => o.Parent); dataContext.LoadOptions = loadOptions; IQueryable<Child1> children = from child in dataContext.Child1 select child; I need to load the sibling data as well. One approach I have tried is splitting the query into two LINQ to SQL queries and merging the result sets together (not pretty), however upon accessing the sibling data it is lazy loaded anyway. Adding the sibling load option will issue a query to SQL Server for each Grandchild1 and Child2 record (which is exactly what I am trying to avoid): DataLoadOptions loadOptions = new DataLoadOptions(); loadOptions.LoadWith<Child1>(o => o.GrandChild1List); loadOptions.LoadWith<Child1>(o => o.Parent); loadOptions.LoadWith<Parent>(o => o.Child2List); dataContext.LoadOptions = loadOptions; IQueryable<Child1> children = from child in dataContext.Child1 select child; exec sp_executesql N'SELECT * FROM [dbo].[Child2] AS [t0] WHERE [t0].[ForeignKeyToParent] = @p0',N'@p0 int',@p0=1 exec sp_executesql N'SELECT * FROM [dbo].[Child2] AS [t0] WHERE [t0].[ForeignKeyToParent] = @p0',N'@p0 int',@p0=2 exec sp_executesql N'SELECT * FROM [dbo].[Child2] AS [t0] WHERE [t0].[ForeignKeyToParent] = @p0',N'@p0 int',@p0=3 exec sp_executesql N'SELECT * FROM [dbo].[Child2] AS [t0] WHERE [t0].[ForeignKeyToParent] = @p0',N'@p0 int',@p0=4 I've also written LINQ to SQL queries to join in all of the data in hopes that it would eager load the data, however when the LINQ to SQL EntitySet of Child2 or Grandchild1 are accessed it lazy loads the data. The reason for returning the IList<Child1> is to hydrate business objects. My thoughts are I am either: Approaching this problem the wrong way. Have the option of calling a stored procedure? My organization should not be using LINQ to SQL as an ORM? Any help is greatly appreciated. Thank you, -Scott

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  • Linq PredicateBuilder with conditional AND, OR and NOT filters.

    - by richeym
    We have a project using LINQ to SQL, for which I need to rewrite a couple of search pages to allow the client to select whether they wish to perform an and or an or search. I though about redoing the LINQ queries using PredicateBuilder and have got this working pretty well I think. I effectively have a class containing my predicates, e.g.: internal static Expression<Func<Job, bool>> Description(string term) { return p => p.Description.Contains(term); } To perform the search i'm doing this (some code omitted for brevity): public Expression<Func<Job, bool>> ToLinqExpression() { var predicates = new List<Expression<Func<Job, bool>>>(); // build up predicates here if (SearchType == SearchType.And) { query = PredicateBuilder.True<Job>(); } else { query = PredicateBuilder.False<Job>(); } foreach (var predicate in predicates) { if (SearchType == SearchType.And) { query = query.And(predicate); } else { query = query.Or(predicate); } } return query; } While i'm reasonably happy with this, I have two concerns: The if/else blocks that evaluate a SearchType property feel like they could be a potential code smell. The client is now insisting on being able to perform 'and not' / 'or not' searches. To address point 2, I think I could do this by simply rewriting my expressions, e.g.: internal static Expression<Func<Job, bool>> Description(string term, bool invert) { if (invert) { return p => !p.Description.Contains(term); } else { return p => p.Description.Contains(term); } } However this feels like a bit of a kludge, which usually means there's a better solution out there. Can anyone recommend how this could be improved? I'm aware of dynamic LINQ, but I don't really want to lose LINQ's strong typing.

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  • How do I use Linq-to-sql to iterate db records?

    - by Seth Spearman
    I asked on SO a few days ago what was the simplest quickest way to build a wrapper around a recently completed database. I took the advice and used sqlmetal to build linq classes around my database design. Now I am having two problems. One, I don't know LINQ. And, two, I have been shocked to realize how hard it is to learn. I have a book on LINQ (Linq In Action by Manning) and it has helped some but at the end of the day it is going to take me a couple of weeks to get traction and I need to make some progress on my project today. So, I am looking for some help getting started. Click HERE To see my simple database schema. Click HERE to see the vb class that was generated for the schema. My needs are simple. I have a console app. The main table is the SupplyModel table. Most of the other tables are child tables of the SupplyModel table. I want to iterate through each of Supply Model records. I want to grab the data for a supply model and then DoStuff with the data. And I also need to iterate through the child records, for each supply model, for example the NumberedInventories and DoStuff with that as well. I need help doing this in VB rather than C# if possible. I am not looking for the whole solution...if you can supply a couple of code-snippets to get me on my way that would be great. Thanks for your help. Seth

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  • Entity Framework LINQ Query using Custom C# Class Method - Once yes, once no - because executing on the client or in SQL?

    - by BrooklynDev
    I have two Entity Framework 4 Linq queries I wrote that make use of a custom class method, one works and one does not: The custom method is: public static DateTime GetLastReadToDate(string fbaUsername, Discussion discussion) { return (discussion.DiscussionUserReads.Where(dur => dur.User.aspnet_User.UserName == fbaUsername).FirstOrDefault() ?? new DiscussionUserRead { ReadToDate = DateTime.Now.AddYears(-99) }).ReadToDate; } The linq query that works calls a from after a from, the equivalent of SelectMany(): from g in oc.Users.Where(u => u.aspnet_User.UserName == fbaUsername).First().Groups from d in g.Discussions select new { UnReadPostCount = d.Posts.Where(p => p.CreatedDate > DiscussionRepository.GetLastReadToDate(fbaUsername, p.Discussion)).Count() }; The query that does not work is more like a regular select: from d in oc.Discussions where d.Group.Name == "Student" select new { UnReadPostCount = d.Posts.Where(p => p.CreatedDate > DiscussionRepository.GetLastReadToDate(fbaUsername, p.Discussion)).Count(), }; The error I get is: LINQ to Entities does not recognize the method 'System.DateTime GetLastReadToDate(System.String, Discussion)' method, and this method cannot be translated into a store expression. My question is, why am I able to use my custom GetLastReadToDate() method in the first query and not the second? I suppose this has something to do with what gets executed on the db server and what gets executed on the client? These queries seem to use the GetLastReadToDate() method so similarly though, I'm wondering why would work for the first and not the second, and most importantly if there's a way to factor common query syntax like what's in the GetLastReadToDate() method into a separate location to be reused in several different places LINQ queries. Please note all these queries are sharing the same object context.

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  • Use LINQ, to Sort and Filter items in a List<ReturnItem> collection, based on the values within a Li

    - by Daniel McPherson
    This is tricky to explain. We have a DataTable that contains a user configurable selection of columns, which are not known at compile time. Every column in the DataTable is of type String. We need to convert this DataTable into a strongly typed Collection of "ReturnItem" objects so that we can then sort and filter using LINQ for use in our application. We have made some progress as follows: We started with the basic DataTable. We then process the DataTable, creating a new "ReturnItem" object for each row This "ReturnItem" object has just two properties: ID ( string ) and Columns( List(object) ). The properties collection contains one entry for each column, representing a single DataRow. Each property is made Strongly Typed (int, string, datetime, etc). For example it would add a new "DateTime" object to the "ReturnItem" Columns List containing the value of the "Created" Datatable Column. The result is a List(ReturnItem) that we would then like to be able to Sort and Filter using LINQ based on the value in one of the properties, for example, sort on "Created" date. We have been using the LINQ Dynamic Query Library, which gets us so far, but it doesn't look like the way forward because we are using it over a List Collection of objects. Basically, my question boils down to: How can I use LINQ, to Sort and Filter items in a List(ReturnItem) collection, based on the values within a List(object) property which is part of the ReturnItem class?

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  • LINQ to SQL exception: System.OutOfMemoryException

    - by Adam
    Not sure why I keep getting an OutOfMemory exception. I'm using ASP.NET MVC with LINQ to SQL. Here's some of the stack trace: [OutOfMemoryException: Exception of type 'System.OutOfMemoryException' was thrown.] System.Runtime.CompilerServices.RuntimeHelpers._CompileMethod(IntPtr method) +0 System.Reflection.Emit.DynamicMethod.CreateDelegate(Type delegateType) +7652553 System.Data.Linq.SqlClient.ObjectReaderCompiler.Compile(SqlExpression expression, Type elementType) +442 System.Data.Linq.SqlClient.SqlProvider.GetReaderFactory(SqlNode node, Type elemType) +100 System.Data.Linq.SqlClient.SqlProvider.System.Data.Linq.Provider.IProvider.Execute(Expression query) +253 System.Data.Linq.Table1.System.Linq.IQueryProvider.Execute(Expression expression) +49 System.Linq.Queryable.Single(IQueryable1 source, Expression`1 predicate) +301 WorkGrabber.Web.Models.WorkGrabberDataContext.GetJob(Int32 id) +233 WorkGrabber.Web.Controllers.BidsController.New(Int32 jobId) +19

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  • What's the next big thing after LINQ?

    - by Leniel Macaferi
    I started using LINQ (Language Integrated Query) when it was still in beta, more specifically Microsoft .NET LINQ Preview (May 2006). Almost 4 years have passed and here we are using LINQ in a lot of projects for the most diverse tasks. I even wrote my final college project based on LINQ. You see how I like it. LINQ and more recently PLINQ (Parallel LINQ) give our jobs a great boost when it comes to more programming power and less lines of code leading us to more expressive and readable code. I keep thinking what could be the next big language improvement for C# after LINQ. I know there are some promissing language features coming as Code Contracts, etc, but nothing having the impact that LINQ had. What do you think could be the next big thing?

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  • LINQ – TakeWhile and SkipWhile methods

    - by nmarun
    I happened to read about these methods on Vikram's blog and tried testing it. Somehow when I saw the output, things did not seem to add up right. I’m writing this blog to show the actual workings of these methods. Let’s take the same example as showing in Vikram’s blog and I’ll build around it. 1: int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 }; 2:  3: foreach(var number in numbers.TakeWhile(n => n < 7)) 4: { 5: Console.WriteLine(number); 6: } Now, the way I (incorrectly) read the upper bound condition in the foreach loop was: ‘Give me all numbers that pass the condition of n<7’. So I was expecting the answer to be: 5, 4, 1, 3, 2, 0. But when I run the application, I see only: 5, 4, 1,3. Turns out I was wrong (happens at least once a day). The documentation on the method says ‘Returns elements from a sequence as long as a specified condition is true. To show in code, my interpretation was the below code’: 1: foreach (var number in numbers) 2: { 3: if (number < 7) 4: { 5: Console.WriteLine(number); 6: } 7: } But the actual implementation is: 1: foreach(var number in numbers) 2: { 3: if(number < 7) 4: { 5: Console.WriteLine(number); 6: break; 7: } 8: } So there it is, another situation where one simple word makes a difference of a whole world. The SkipWhile method has been implemented in a similar way – ‘Bypasses elements in a sequence as long as a specified condition is true and then returns the remaining elements’ and not ‘Bypasses elements in a sequence where a specified condition is true and then returns the remaining elements’. (Subtle.. very very subtle). It’s feels strange saying this, but hope very few require to read this article to understand these methods.

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  • LINQ for SQL Developers and DBA’s

    - by AtulThakor
    Firstly I’d just like to thank the guys who organise the SQL Server User Group (Martin/Tony/Chris) and for giving me the opportunity to speak at the recent event. Sorry about the slides taking so long but here they are along with some extra information. Firstly the demo’s were all done using LINQPad 4.0 which can be downloaded here: http://www.linqpad.net/ There are 2 versions 3.5/4.0 With 3.5 you should be able to replicate the problem I showed where a query using a parameter which is X characters long would create a different execution plan to a query which uses a parameter which is Y characters long, otherwise I would just use 4.0 The sample database used is AdventureWorksLT2008 which can be downloaded from here: http://msftdbprodsamples.codeplex.com/releases/view/37109 The scripts have been named so that you can select the appropriate way to run them i.e.: C# expression / C#statement, each script can be run individually be highlighting the query and clicking the play symbol or hitting F5. Scripts and Slides: http://sqlblogcasts.com/blogs/atulthakor/An%20Introduction%20to%20LINQ.zip Please don't hesitate in sending any questions via email/twitter, I’ll try my best to answer your questions! Thanks, Atul

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  • Grouping data in LINQ with the help of group keyword

    - by vik20000in
    While working with any kind of advanced query grouping is a very important factor. Grouping helps in executing special function like sum, max average etc to be performed on certain groups of data inside the date result set. Grouping is done with the help of the Group method. Below is an example of the basic group functionality.     int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };         var numberGroups =         from num in numbers         group num by num % 5 into numGroup         select new { Remainder = numGroup.Key, Numbers = numGroup };  In the above example we have grouped the values based on the reminder left over when divided by 5. First we are grouping the values based on the reminder when divided by 5 into the numgroup variable.  numGroup.Key gives the value of the key on which the grouping has been applied. And the numGroup itself contains all the records that are contained in that group. Below is another example to explain the same. string[] words = { "blueberry", "abacus", "banana", "apple", "cheese" };         var wordGroups =         from num in words         group num by num[0] into grp         select new { FirstLetter = grp.Key, Words = grp }; In the above example we are grouping the value with the first character of the string (num[0]). Just like the order operator the group by clause also allows us to write our own logic for the Equal comparison (That means we can group Item by ignoring case also by writing out own implementation). For this we need to pass an object that implements the IEqualityComparer<string> interface. Below is an example. public class AnagramEqualityComparer : IEqualityComparer<string> {     public bool Equals(string x, string y) {         return getCanonicalString(x) == getCanonicalString(y);     }      public int GetHashCode(string obj) {         return getCanonicalString(obj).GetHashCode();     }         private string getCanonicalString(string word) {         char[] wordChars = word.ToCharArray();         Array.Sort<char>(wordChars);         return new string(wordChars);     } }  string[] anagrams = {"from   ", " salt", " earn", "  last   ", " near "}; var orderGroups = anagrams.GroupBy(w => w.Trim(), new AnagramEqualityComparer()); Vikram  

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  • Enhancing performance in Entity Framework applications by precompiling LINQ to Entities queries

    - by nikolaosk
    This is going to be the tenth post of a series of posts regarding ASP.Net and the Entity Framework and how we can use Entity Framework to access our datastore. You can find the first one here , the second one here , the third one here , the fourth one here , the fifth one here ,the sixth one here ,the seventh one here ,the eighth one here and the ninth one here . I have a post regarding ASP.Net and EntityDataSource . You can read it here .I have 3 more posts on Profiling Entity Framework applications...(read more)

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  • LINQ: Enhancing Distinct With The SelectorEqualityComparer

    - by Paulo Morgado
    On my last post, I introduced the PredicateEqualityComparer and a Distinct extension method that receives a predicate to internally create a PredicateEqualityComparer to filter elements. Using the predicate, greatly improves readability, conciseness and expressiveness of the queries, but it can be even better. Most of the times, we don’t want to provide a comparison method but just to extract the comaprison key for the elements. So, I developed a SelectorEqualityComparer that takes a method that extracts the key value for each element. Something like this: public class SelectorEqualityComparer<TSource, Tkey> : EqualityComparer<TSource> where Tkey : IEquatable<Tkey> { private Func<TSource, Tkey> selector; public SelectorEqualityComparer(Func<TSource, Tkey> selector) : base() { this.selector = selector; } public override bool Equals(TSource x, TSource y) { Tkey xKey = this.GetKey(x); Tkey yKey = this.GetKey(y); if (xKey != null) { return ((yKey != null) && xKey.Equals(yKey)); } return (yKey == null); } public override int GetHashCode(TSource obj) { Tkey key = this.GetKey(obj); return (key == null) ? 0 : key.GetHashCode(); } public override bool Equals(object obj) { SelectorEqualityComparer<TSource, Tkey> comparer = obj as SelectorEqualityComparer<TSource, Tkey>; return (comparer != null); } public override int GetHashCode() { return base.GetType().Name.GetHashCode(); } private Tkey GetKey(TSource obj) { return (obj == null) ? (Tkey)(object)null : this.selector(obj); } } Now I can write code like this: .Distinct(new SelectorEqualityComparer<Source, Key>(x => x.Field)) And, for improved readability, conciseness and expressiveness and support for anonymous types the corresponding Distinct extension method: public static IEnumerable<TSource> Distinct<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> selector) where TKey : IEquatable<TKey> { return source.Distinct(new SelectorEqualityComparer<TSource, TKey>(selector)); } And the query is now written like this: .Distinct(x => x.Field) For most usages, it’s simpler than using a predicate.

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  • how to update child records when updating the Master table using Linq [closed]

    - by user20358
    I currently use a general repositry class that can update only a single table like so public abstract class MyRepository<T> : IRepository<T> where T : class { protected IObjectSet<T> _objectSet; protected ObjectContext _context; public MyRepository(ObjectContext Context) { _objectSet = Context.CreateObjectSet<T>(); _context = Context; } public IQueryable<T> GetAll() { return _objectSet.AsQueryable(); } public IQueryable<T> Find(Expression<Func<T, bool>> filter) { return _objectSet.Where(filter); } public void Add(T entity) { _objectSet.AddObject(entity); _context.ObjectStateManager.ChangeObjectState(entity, System.Data.EntityState.Added); _context.SaveChanges(); } public void Update(T entity) { _context.ObjectStateManager.ChangeObjectState(entity, System.Data.EntityState.Modified); _context.SaveChanges(); } public void Delete(T entity) { _objectSet.Attach(entity); _context.ObjectStateManager.ChangeObjectState(entity, System.Data.EntityState.Deleted); _objectSet.DeleteObject(entity); _context.SaveChanges(); } } For every table class generated by my EDMX designer I create another class like this public class CustomerRepo : MyRepository<Customer> { public CustomerRepo (ObjectContext context) : base(context) { } } for any updates that I need to make to a particular table I do this: Customer CustomerObj = new Customer(); CustomerObj.Prop1 = ... CustomerObj.Prop2 = ... CustomerObj.Prop3 = ... CustomerRepo.Update(CustomerObj); This works perfectly well when I am updating just to the specific table called Customer. Now if I need to also update each row of another table which is a child of Customer called Orders what changes do I need to make to the class MyRepository. Orders table will have multiple records for a Customer record and multiple fields too, say for example Field1, Field2, Field3. So my questions are: 1.) If I only need to update Field1 of the Orders table for some rows based on a condition and Field2 for some other rows based on a different condition then what changes I need to do? 2.) If there is no such condition and all child rows need to be updated with the same value for all rows then what changes do I need to do? Thanks for taking the time. Look forward to your inputs...

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  • LINQ – Skip() and Take() methods

    - by nmarun
    I had this issue recently where I have an array of integers and I’m doing some Skip(n) and then a Take(m) on the collection. Here’s an abstraction of the code: 1: int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 }; 2: var taken = numbers.Skip(3).Take(3); 3: foreach (var i in taken) 4: { 5: Console.WriteLine(i); 6: } The output is as expected: 3, 9, 8 – skip the first three and then take the next three items. But, what happens if I do something like: 1: var taken = numbers.Skip(7).Take(5); In English – skip the first seven and the take the next 5 items from an array that contains only 10 elements. Think it’ll throw the IndexOutOfRangeException exception? Nope. These extension methods are a little smarter than that. Even though the user has requested more elements than what exists in the collection, the Take method only returns the first three thereby making the output of the program as: 7, 2, 0. The scenario is handled similarly when you do: 1: var taken = numbers.Take(5).Skip(7); This one takes the first 5 elements from the numbers array and then skips 7 of them. This is what is looks like in the debug mode: Just wanted to share this behavior.

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  • Outer Join is not working in Linq Query: The method 'Join' cannot follow the method 'SelectMany' or is not supported

    - by Scorpion
    I am writing the Linq query as below: But on run its throwing the following error: The method 'Join' cannot follow the method 'SelectMany' or is not supported. Try writing the query in terms of supported methods or call the 'AsEnumerable' or 'ToList' method before calling unsupported methods. LINQ from a in AccountSet join sm in new_schoolMemberSet on a.AccountId equals sm.new_OrganisationId.Id into ps from suboc in ps.DefaultIfEmpty() join sr in new_schoolRoleSet on suboc.new_SchoolRoleId.Id equals sr.new_schoolRoleId where sr.new_name == "Manager" where a.new_OrganisationType.Value == 430870007 select new { a.AccountId, a.new_OrganisationType.Value } I am expecting the result as below: I never used the Outer join in Linq before. So please correct me if I am doing it wrong. Thanks

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  • Will this LINQ-TO-SQL query fetch all records from the table ?

    - by Puneet Dudeja
    public long GetNewCRN() { return ((from c in DataContext.GetTable<Cust_Master>() select c.CUSTSERH_CRN).Max() + 1); } Will this Linq to Sql query fetch all records from the table first and then select the maximum of the column ? If yes, then isn't it a bad idea using linq to sql instead of normal SqlCommand ? Or is there any other way of doing it in linq to sql ? When I attach Console.Out, I see nothing(command prompt does not even open). But when I include following:- context.Log = new System.IO.StreamWriter("d:\\abcd.txt"); I get an error, that "The process can not access the file because it is being used by another process" and that process is "w3wp.exe". How can I see the sql commands being executed by DataContext then ?

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  • Hype and LINQ

    - by Tony Davis
    "Tired of querying in antiquated SQL?" I blinked in astonishment when I saw this headline on the LinqPad site. Warming to its theme, the site suggests that what we need is to "kiss goodbye to SSMS", and instead use LINQ, a modern query language! Elsewhere, there is an article entitled "Why LINQ beats SQL". The designers of LINQ, along with many DBAs, would, I'm sure, cringe with embarrassment at the suggestion that LINQ and SQL are, in any sense, competitive ways of doing the same thing. In fact what LINQ really is, at last, is an efficient, declarative language for C# and VB programmers to access or manipulate data in objects, local data stores, ORMs, web services, data repositories, and, yes, even relational databases. The fact is that LINQ is essentially declarative programming in a .NET language, and so in many ways encourages developers into a "SQL-like" mindset, even though they are not directly writing SQL. In place of imperative logic and loops, it uses various expressions, operators and declarative logic to build up an "expression tree" describing only what data is required, not the operations to be performed to get it. This expression tree is then parsed by the language compiler, and the result, when used against a relational database, is a SQL string that, while perhaps not always perfect, is often correctly parameterized and certainly no less "optimal" than what is achieved when a developer applies blunt, imperative logic to the SQL language. From a developer standpoint, it is a mistake to consider LINQ simply as a substitute means of querying SQL Server. The strength of LINQ is that that can be used to access any data source, for which a LINQ provider exists. Microsoft supplies built-in providers to access not just SQL Server, but also XML documents, .NET objects, ADO.NET datasets, and Entity Framework elements. LINQ-to-Objects is particularly interesting in that it allows a declarative means to access and manipulate arrays, collections and so on. Furthermore, as Michael Sorens points out in his excellent article on LINQ, there a whole host of third-party LINQ providers, that offers a simple way to get at data in Excel, Google, Flickr and much more, without having to learn a new interface or language. Of course, the need to be generic enough to deal with a range of data sources, from something as mundane as a text file to as esoteric as a relational database, means that LINQ is a compromise and so has inherent limitations. However, it is a powerful and beautifully compact language and one that, at least in its "query syntax" guise, is accessible to developers and DBAs alike. Perhaps there is still hope that LINQ can fulfill Phil Factor's lobster-induced fantasy of a language that will allow us to "treat all data objects, whether Word files, Excel files, XML, relational databases, text files, HTML files, registry files, LDAPs, Outlook and so on, in the same logical way, as linked databases, and extract the metadata, create the entities and relationships in the same way, and use the same SQL syntax to interrogate, create, read, write and update them." Cheers, Tony.

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  • Extend linq-to-sql partial class to avoid writing a property?

    - by Curtis White
    I have a linq-to-sql class. I have a property "Password" for which I want to call the underlying ASP.NET Membership provider. Thus, I do not want this property written out directly but via my own code. I basically want to create a facade/proxy for this property such that I may use the underlying membership provider or a custom stored procedure. I want to accomplish without modifying the LINQ-TO-SQL designer generated code, if at all possible.

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  • Linq 2 Sybase ASE database? What are the options?

    - by Scott Weinstein
    I have a need to query an existing Sybase ASE database and would like to use Linq syntax for my data retrival. I don't need write access, nor do I need the full set of Linq operators, just Select(), SelectMany(), Where(), and GroupJoin() What are options are available? In particular, I'm wondering about nHibernate and building a new Linq2Sybase provider based on the IQ toolkit.

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  • What is the difference between these 2 XML LINQ Queries?

    - by Jon
    I have the 2 following LINQ queries and I haven't quite got my head around LINQ so what is the difference between the 2 approaches below? Is there a circumstance where one approach is better than another? ChequeDocument.Descendants("ERRORS").Where(x=>(string)x.Attribute("D") == "").Count(); (from x in ChequeDocument.Descendants("ERRORS") where (string)x.Attribute("D") == "" select x).Count())

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  • How to use LINQ for CRUD with a simple SQL table?

    - by Rob Ferno
    Every LINQ blog I found there seemed around 2 years old, I understand the syntax but need more direction on creating the SQL mapping and context classes. I just need to use LINQ for 2 SQL tables I have, nothing complicated. Do folks write the SQL mapping classes by hand for such cases or is there a decent tool for this? Can someone point me in the right direction?

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  • Is it just me? I find LINQ to XML to be sort of cumbersome, compared to XPath.

    - by Cheeso
    I am a C# programmer, so I don't get to take advantage of the cool XML syntax in VB. Dim itemList1 = From item In rss.<rss>.<channel>.<item> _ Where item.<description>.Value.Contains("LINQ") Or _ item.<title>.Value.Contains("LINQ") Using C#, I find XPath to be easier to think about, easier to code, easier to understand, than performing a multi-nested select using LINQ to XML. Look at this syntax, it looks like Greek swearing: var waypoints = from waypoint in gpxDoc.Descendants(gpx + "wpt") select new { Latitude = waypoint.Attribute("lat").Value, Longitude = waypoint.Attribute("lon").Value, Elevation = waypoint.Element(gpx + "ele") != null ? waypoint.Element(gpx + "ele").Value : null, Name = waypoint.Element(gpx + "name") != null ? waypoint.Element(gpx + "name").Value : null, Dt = waypoint.Element(gpx + "cmt") != null ? waypoint.Element(gpx + "cmt").Value : null }; All the casting, the heavy syntax, the possibility for NullPointerExceptions. None of this happens with XPath. I like LINQ in general, and I use it on object collections and databases, but my first go-round with querying XML led me right back to XPath. Is it just me? Am I missing something? EDIT: someone voted to close this as "not a real question". But it is a real question, stated clearly. The question is: Am I misunderstanding something with LINQ to XML?

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