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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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  • Plain-English tutorial on artificial neural networks?

    - by Stuart
    I've Googled, StackOverflowed, everything, and I cannot seem to find a tutorial I can understand. I understand the concept of genetic algorithms, and how to implement them, (Though I haven't tried) but I cannot grasp the concept of neural networks. I know vaguely how they work... And that's about it. Could someone direct me to a tutorial that could help someone who has not even graduated middle school yet? Sure, I'm several years ahead of the majority of people my grade, but I don't understand summation, (which I apparently need if I don't want a simple binary output) vectors, and other things that I apparently should know. Is there a simple, bare-bones tutorial for neural networks? After I learn the basics, I'll proceed to more difficult ones. Preferably, they would be in Java. 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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  • How can I stop an auto-generated Linq to SQL class from loading ALL data?

    - by Gary McGill
    DUPLICATE of http://stackoverflow.com/questions/2433422/how-can-i-stop-an-auto-generated-linq-to-sql-class-from-loading-all-data post answers there! I have an ASP.NET MVC project, much like the NerdDinner tutorial example. (I'm using MVC 2, but followed the NerdDinner tutorial in order to create it). As per the instructions in part 3 of the tutorial, I've created a Linq-to-SQL model of my database by creating a "Linq to SQL Classes" (.dbml) surface, and dropping my database tables onto it. The designer has automatically added relationships between the generated classes based on my database tables. Let's say that my classes are as per the NerdDinner example, so I have Dinner and RSVP tables, where each Dinner record is associated with many RSVP records - hence in the generated classes, the Dinner object has a RSVPs property which is a list of RSVP objects. My problem is this: it appears (and I'd be gladly proved wrong on this) that as soon as I access a Dinner object, it's loading all of the corresponding RSVP objects, even if I don't use the RSVPs member. First question: is this really the default behavior for the generated classes? In my particular situation, the object graph contains many more tables (which have an order of magnitude more records), and so this is disastrous behaviour - I'd be loading tons of data when all I want to do is show the details of a single parent record. Second question: are there any properties exposed through the designer UI that would let me modify this behavior? (I can't find any). Third question: I've seen a description of how to control the loading of related records in a DataContext by using a DataShape object associated with the DataContext. Is that what I'm meant to do, and if so are there any tutorials like the NerdDinner one that would show not only how to do it, but also suggest a 'pattern' for normal use?

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  • How can I stop an auto-generated Linq to SQL class from loading ALL data?

    - by Gary McGill
    I have an ASP.NET MVC project, much like the NerdDinner tutorial example. (I'm using MVC 2, but followed the NerdDinner tutorial in order to create it). As per the instructions in part 3 of the tutorial, I've created a Linq-to-SQL model of my database by creating a "Linq to SQL Classes" (.dbml) surface, and dropping my database tables onto it. The designer has automatically added relationships between the generated classes based on my database tables. Let's say that my classes are as per the NerdDinner example, so I have Dinner and RSVP tables, where each Dinner record is associated with many RSVP records - hence in the generated classes, the Dinner object has a RSVPs property which is a list of RSVP objects. My problem is this: it appears (and I'd be gladly proved wrong on this) that as soon as I access a Dinner object, it's loading all of the corresponding RSVP objects, even if I don't use the RSVPs member. First question: is this really the default behavior for the generated classes? In my particular situation, the object graph contains many more tables (which have an order of magnitude more records), and so this is disastrous behaviour - I'd be loading tons of data when all I want to do is show the details of a single parent record. Second question: are there any properties exposed through the designer UI that would let me modify this behavior? (I can't find any). Third question: I've seen a description of how to control the loading of related records in a DataContext by using a DataShape object associated with the DataContext. Is that what I'm meant to do, and if so are there any tutorials like the NerdDinner one that would show not only how to do it, but also suggest a 'pattern' for normal use?

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  • How can I create a dynamic LINQ query in C# with possible multiple group by clauses?

    - by FordPrefect141
    I have been a programmer for some years now but I am a newcomer to LINQ and C# so forgive me if my question sounds particularly stupid. I hope someone may be able to point me in the right direction. My task is to come up with the ability to form a dynamic multiple group by linq query within a c# script using a generic list as a source. For example, say I have a list containing multiple items with the following structure: FieldChar1 - character FieldChar2 - character FieldChar3 - character FieldNum1 - numeric FieldNum2 - numeric In a nutshell I want to be able to create a LINQ query that will sum FieldNum1 and FieldNum2 grouped by any one, two or all three of the FieldChar fields that will be decided at runtime depending on the users requirements as well as selecting the FieldChar fields in the same query. I have the dynamic.cs in my project which icludes a GroupByMany extension method but I have to admit I am really not sure how to put these to use. I am able to get the desired results if I use a query with hard-wired group by requests but not dynamically. Apologies for any erroneous nomenclature, I am new to this language but any advice would be most welcome. Many thanks Alex

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  • LINQ thinks I need an extra INNER JOIN, but why?

    - by Saurabh Kumar
    I have a LINQ query, which for some reason is generating an extra/duplicatre INNER JOIN. This is causing the query to not return the expected output. If I manually comment that extra JOIN from the generated SQL, then I get seemingly correct output. Can you detect what I might have done i nthis LINQ to have cuased this extra JOIN? Thanks. Here is my approx LINQ var ids = context.Code.Where(predicate); var rs = from r in ids group r by new { r.phonenumbers.person.PersonID} into g let matchcount=g.Select(p => p.phonenumbers.PhoneNum).Distinct().Count() where matchcount ==2 select new { personid = g.Key }; and here is the generated SQL (the duplicate join is [t7]) Declare @p1 VarChar(10)='Home' Declare @p2 VarChar(10)='111' Declare @p3 VarChar(10)='Office' Declare @p4 VarChar(10)='222' Declare @p5 int=2 SELECT [t9].[PersonID] AS [pid] FROM ( SELECT [t3].[PersonID], ( SELECT COUNT(*) FROM ( SELECT DISTINCT [t7].[PhoneValue] FROM [dbo].[Person] AS [t4] INNER JOIN [dbo].[PersonPhoneNumber] AS [t5] ON [t5].[PersonID] = [t4].[PersonID] INNER JOIN [dbo].[CodeMaster] AS [t6] ON [t6].[Code] = [t5].[PhoneType] INNER JOIN [dbo].[PersonPhoneNumber] AS [t7] ON [t7].[PersonID] = [t4].[PersonID] WHERE ([t3].[PersonID] = [t4].[PersonID]) AND ([t6].[Enumeration] = @p0) AND ((([t6].[CodeDescription] = @p1) AND ([t5].[PhoneValue] = @p2)) OR (([t6].[CodeDescription] = @p3) AND ([t5].[PhoneValue] = @p4))) ) AS [t8] ) AS [value] FROM ( SELECT [t0].[PersonID] FROM [dbo].[Person] AS [t0] INNER JOIN [dbo].[PersonPhoneNumber] AS [t1] ON [t1].[PersonID] = [t0].[PersonID] INNER JOIN [dbo].[CodeMaster] AS [t2] ON [t2].[Code] = [t1].[PhoneType] WHERE ([t2].[Enumeration] = @p0) AND ((([t2].[CodeDescription] = @p1) AND ([t1].[PhoneValue] = @p2)) OR (([t2].[CodeDescription] = @p3) AND ([t1].[PhoneValue] = @p4))) GROUP BY [t0].[PersonID] ) AS [t3] ) AS [t9] WHERE [t9].[value] = @p5

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  • Linq-to-SQL produces bad SQL?

    - by strager
    I am trying to run a Linq-to-SQL query, but when the query is evaluated, I get the following exception: System.Data.OleDb.OleDbException was unhandled Message=The SELECT statement includes a reserved word or an argument name that is misspelled or missing, or the punctuation is incorrect. Source=Microsoft JET Database Engine ErrorCode=-2147217900 StackTrace: at System.Data.OleDb.OleDbCommand.ExecuteCommandTextErrorHandling(OleDbHResult hr) at System.Data.OleDb.OleDbCommand.ExecuteCommandTextForSingleResult(tagDBPARAMS dbParams, Object& executeResult) at System.Data.OleDb.OleDbCommand.ExecuteCommandText(Object& executeResult) at System.Data.OleDb.OleDbCommand.ExecuteCommand(CommandBehavior behavior, Object& executeResult) at System.Data.OleDb.OleDbCommand.ExecuteReaderInternal(CommandBehavior behavior, String method) at System.Data.OleDb.OleDbCommand.ExecuteReader(CommandBehavior behavior) at System.Data.OleDb.OleDbCommand.ExecuteDbDataReader(CommandBehavior behavior) at System.Data.Common.DbCommand.ExecuteReader() at System.Data.Linq.SqlClient.SqlProvider.Execute(Expression query, QueryInfo queryInfo, IObjectReaderFactory factory, Object[] parentArgs, Object[] userArgs, ICompiledSubQuery[] subQueries, Object lastResult) at System.Data.Linq.SqlClient.SqlProvider.ExecuteAll(Expression query, QueryInfo[] queryInfos, IObjectReaderFactory factory, Object[] userArguments, ICompiledSubQuery[] subQueries) at System.Data.Linq.SqlClient.SqlProvider.System.Data.Linq.Provider.IProvider.Execute(Expression query) at System.Data.Linq.DataQuery`1.System.Linq.IQueryProvider.Execute[S](Expression expression) at System.Linq.Queryable.FirstOrDefault[TSource](IQueryable`1 source) at xxx.InventoryPopulator`2.Clear(String barcode) in F:\Projects\C#\xxx\xxx\InventoryPopulator.cs:line 38 [..etc..] InnerException: The debugger shows my query is: SELECT [t0].[SupplierID] AS [Id], [t0].[SupplierSKU] AS [Sku], [t0].[LocalSKU] AS [LocalSku], [t0].[ManufacturersBarcode] AS [Barcode], [t0].[QuantityAvailable] FROM [inventorySupplier] AS [t0] WHERE [t0].[ManufacturersBarcode] = @p0 And the Linq query which generates the above is: var items = from item in this.supplierItems where item.Barcode == barcode select item; How do I fix my query?

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  • Is this an example of LINQ-to-SQL?

    - by Edward Tanguay
    I made a little WPF application with a SQL CE database. I built the following code with LINQ to get data out of the database, which was surprisingly easy. So I thought "this must be LINQ-to-SQL". Then I did "add item" and added a "LINQ-to-SQL classes" .dbml file, dragged my table onto the Object Relational Designer but it said, "The selected object uses an unsupported data provider." So then I questioned whether or not the following code actually is LINQ-to-SQL, since it indeed allows me to access data from my SQL CE database file, yet officially "LINQ-to-SQL" seems to be unsupported for SQL CE. So is the following "LINQ-to-SQL" or not? using System.Linq; using System.Data.Linq; using System.Data.Linq.Mapping; using System.Windows; namespace TestLinq22 { public partial class Window1 : Window { public Window1() { InitializeComponent(); MainDB db = new MainDB(@"Data Source=App_Data\Main.sdf"); var customers = from c in db.Customers select new {c.FirstName, c.LastName}; TheListBox.ItemsSource = customers; } } [Database(Name = "MainDB")] public class MainDB : DataContext { public MainDB(string connection) : base(connection) { } public Table<Customers> Customers; } [Table(Name = "Customers")] public class Customers { [Column(DbType = "varchar(100)")] public string FirstName; [Column(DbType = "varchar(100)")] public string LastName; } }

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  • Pass Linq Expression to a function

    - by Kushan Hasithe Fernando
    I want to pass a property list of a class to a function. with in the function based on property list I'm going to generate a query. As exactly same functionality in Linq Select method. Here I'm gonna implement this for Ingress Database. As an example, in front end I wanna run a select as this, My Entity Class is like this public class Customer { [System.Data.Linq.Mapping.ColumnAttribute(Name="Id",IsPrimaryKey=true)] public string Id { get; set; } [System.Data.Linq.Mapping.ColumnAttribute(Name = "Name")] public string Name { get; set; } [System.Data.Linq.Mapping.ColumnAttribute(Name = "Address")] public string Address { get; set; } [System.Data.Linq.Mapping.ColumnAttribute(Name = "Email")] public string Email { get; set; } [System.Data.Linq.Mapping.ColumnAttribute(Name = "Mobile")] public string Mobile { get; set; } } I wanna call a Select function like this, var result = dataAccessService.Select<Customer>(C=>C.Name,C.Address); then,using result I can get the Name and Address properties' values. I think my Select function should looks like this, ( *I think this should done using Linq Expression. But im not sure what are the input parameter and return type. * ) Class DataAccessService { // I'm not sure about this return type and input types, generic types. public TResult Select<TSource,TResult>(Expression<Func<TSource,TResult>> selector) { // Here using the property list, // I can get the ColumnAttribute name value and I can generate a select query. } } This is a attempt to create a functionality like in Linq. But im not an expert in Linq Expressions. There is a project call DbLinq from MIT, but its a big project and still i couldn't grab anything helpful from that. Can someone please help me to start this, or can someone link me some useful resources to read about this.

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  • How do I tell the cases when it's worth to use LINQ?

    - by Lijo
    Many things in LINQ can be accomplished without the library. But for some scenarios, LINQ is most appropriate. Examples are: SELECT - http://stackoverflow.com/questions/11883262/wrapping-list-items-inside-div-in-a-repeater SelectMany, Contains - http://stackoverflow.com/questions/11778979/better-code-pattern-for-checking-existence-of-value Enumerable.Range - http://stackoverflow.com/questions/11780128/scalable-c-sharp-code-for-creating-array-from-config-file WHERE http://stackoverflow.com/questions/13171850/trim-string-if-a-string-ends-with-a-specific-word What factors to take into account when deciding between LINQ and regular .Net language elements?

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  • What is the most effective order to learn SQL Server, LINQ, and Entity Framework?

    - by user1525474
    I am trying to get some advice on what order I should learn about SQL Server, LINQ, and Entity Framework to be able to better work with ASP.NET Webforms and MVC. From what I've been able to learn so far, many recommend learning LINQ or Entity Framework before learning SQL Server. It also appears that many companies are looking for people with knowledge in LINQ-to-SQL and Entity Framework without mentioning SQL Server. However, my understanding is that LINQ-to-SQL and Entity Framework translate code into SQL Server queries, making this a poor approach. Is there a correct or best order in which to learn these technologies?

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  • Cannot iterate of a collection of Anonymous Types created from a LINQ Query in VB.NET

    - by Atari2600
    Ok everyone, I must be missing something here. Every LINQ example I have seen for VB.NET anonymous types claims I can do something like this: Dim Info As EnumerableRowCollection = pDataSet.Tables(0).AsEnumerable Dim Infos = From a In Info _ Select New With {.Prop1 = a("Prop1"), .Prop2 = a("Prop2"), .Prop3 = a("Prop3") } Now when I go to iterate through the collection(see example below), I get an error that says "Name "x" is not declared. For Each x in Infos ... Next It's like VB.NET doesn't understand that Infos is a collection of anonymous types created by LINQ and wants me to declare "x" as some type. (Wouldn't this defeat the purpose of an anonymous type?) I have added the references to System.Data.Linq and System.Data.DataSetExtensions to my project. Here is what I am importing with the class: Imports System.Linq Imports System.Linq.Enumerable Imports System.Linq.Queryable Imports System.Data.Linq Any ideas?

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  • Linq To SQL - Specified cast is not valid - SingleOrDefault()

    - by NullReference
    I am trying to do the following... Request request = (from r in db.Requests where r.Status == "Processing" && r.Locked == false select r).SingleOrDefault(); It is throwing the following exception... Message: Specified cast is not valid. StackTrace: at System.Data.Linq.SqlClient.SqlProvider.Execute(Expression query, QueryInfo queryInfo, IObjectReaderFactory factory, Object[] parentArgs, Object[] userArgs, ICompiledSubQuery[] subQueries, Object lastResult) at System.Data.Linq.SqlClient.SqlProvider.ExecuteAll(Expression query, QueryInfo[] queryInfos, IObjectReaderFactory factory, Object[] userArguments, ICompiledSubQuery[] subQueries) at System.Data.Linq.SqlClient.SqlProvider.System.Data.Linq.Provider.IProvider.Execute(Expression query) at System.Data.Linq.DataQuery1.System.Linq.IQueryProvider.Execute[S](Expression expression) at System.Linq.Queryable.SingleOrDefault[TSource](IQueryable1 source) at GDRequestProcessor.Worker.GetNextRequest() Can anyone help me? Thanks in advance!

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  • LINQ - Linq to Sql - Specified cast is not valid - Please Help!

    - by thiag0
    I am trying to do the following... Request request = ( from r in db.Requests where r.Status == "Processing" && r.Locked == false select r).SingleOrDefault(); It is throwing the following exception... Message: Specified cast is not valid. StackTrace: at System.Data.Linq.SqlClient.SqlProvider.Execute(Expression query, QueryInfo queryInfo, IObjectReaderFactory factory, Object[] parentArgs, Object[] userArgs, ICompiledSubQuery[] subQueries, Object lastResult) at System.Data.Linq.SqlClient.SqlProvider.ExecuteAll(Expression query, QueryInfo[] queryInfos, IObjectReaderFactory factory, Object[] userArguments, ICompiledSubQuery[] subQueries) at System.Data.Linq.SqlClient.SqlProvider.System.Data.Linq.Provider.IProvider.Execute(Expression query) at System.Data.Linq.DataQuery`1.System.Linq.IQueryProvider.Execute[S](Expression expression) at System.Linq.Queryable.SingleOrDefault[TSource](IQueryable`1 source) at GDRequestProcessor.Worker.GetNextRequest() The .DBML file schema matches my database table that I am trying to select from so I have no clue why I am having this problem. Can anyone help me? Thanks in advance!

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  • Spring MVC Web PetClinic Tutorial?

    - by wuntee
    Is there a tutorial that goes along with the PetClinic application? I have been trying to find one, but google is not helping me today. Specifically, I dont understand things like: @Autowired - what does that even mean? @RequestMapping(method = RequestMethod.GET) public String setupForm(@RequestParam("petId") int petId, ModelMap model) { Pet pet = this.clinic.loadPet(petId); model.addAttribute("pet", pet); return "petForm"; } How can a request return just a string? Shouldnt it need to return some sort of ModelAndView? Or does the application somehow redirect to whatever is returned? A lot of confusing concepts - if there is a tutorial, or video (like spring-security has) that would be very helpful. Thanks.

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