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• LINQ 4 XML - What is the proper way to query deep in the tree structure?

  - by Keith Barrows

  I have an XML structure that is 4 deep: <?xml version="1.0" encoding="utf-8"?> <EmailRuleList xmlns:xsd="EmailRules.xsd"> <TargetPST name="Tech Communities"> <Parse emailAsList="true" useJustDomain="false" fromAddress="false" toAddress="true"> <EmailRule address="@aspadvice.com" folder="Lists, ASP" saveAttachments="false" /> <EmailRule address="@sqladvice.com" folder="Lists, SQL" saveAttachments="false" /> <EmailRule address="@xmladvice.com" folder="Lists, XML" saveAttachments="false" /> </Parse> <Parse emailAsList="false" useJustDomain="false" fromAddress="false" toAddress="true"> <EmailRule address="[email protected]" folder="Special Interest Groups|Northern Colorado Architects Group" saveAttachments="false" /> <EmailRule address="[email protected]" folder="Support|SpamBayes" saveAttachments="false" /> </Parse> <Parse emailAsList="false" useJustDomain="false" fromAddress="true" toAddress="false"> <EmailRule address="[email protected]" folder="Support|GoDaddy" saveAttachments="false" /> <EmailRule address="[email protected]" folder="Support|No-IP.com" saveAttachments="false" /> <EmailRule address="[email protected]" folder="Discussions|Orchard Project" saveAttachments="false" /> </Parse> <Parse emailAsList="false" useJustDomain="true" fromAddress="true" toAddress="false"> <EmailRule address="@agilejournal.com" folder="Newsletters|Agile Journal" saveAttachments="false"/> <EmailRule address="@axosoft.ccsend.com" folder="Newsletters|Axosoft Newsletter" saveAttachments="false"/> <EmailRule address="@axosoft.com" folder="Newsletters|Axosoft Newsletter" saveAttachments="false"/> <EmailRule address="@cmcrossroads.com" folder="Newsletters|CM Crossroads" saveAttachments="false" /> <EmailRule address="@urbancode.com" folder="Newsletters|Urbancode" saveAttachments="false" /> <EmailRule address="@urbancode.ccsend.com" folder="Newsletters|Urbancode" saveAttachments="false" /> <EmailRule address="@Infragistics.com" folder="Newsletters|Infragistics" saveAttachments="false" /> <EmailRule address="@zdnet.online.com" folder="Newsletters|ZDNet Tech Update Today" saveAttachments="false" /> <EmailRule address="@sqlservercentral.com" folder="Newsletters|SQLServerCentral.com" saveAttachments="false" /> <EmailRule address="@simple-talk.com" folder="Newsletters|Simple-Talk Newsletter" saveAttachments="false" /> </Parse> </TargetPST> <TargetPST name="[Sharpen the Saw]"> <Parse emailAsList="false" useJustDomain="false" fromAddress="false" toAddress="true"> <EmailRule address="[email protected]" folder="Head Geek|Job Alerts" saveAttachments="false" /> <EmailRule address="[email protected]" folder="Social|LinkedIn USMC" saveAttachments="false"/> </Parse> <Parse emailAsList="false" useJustDomain="false" fromAddress="true" toAddress="false"> <EmailRule address="[email protected]" folder="Head Geek|Job Alerts" saveAttachments="false" /> <EmailRule address="[email protected]" folder="Head Geek|Job Alerts" saveAttachments="false" /> <EmailRule address="[email protected]" folder="Social|Cruise Critic" saveAttachments="false"/> </Parse> <Parse emailAsList="false" useJustDomain="true" fromAddress="true" toAddress="false"> <EmailRule address="@moody.edu" folder="Social|5 Love Languages" saveAttachments="false" /> <EmailRule address="@postmaster.twitter.com" folder="Social|Twitter" saveAttachments="false"/> <EmailRule address="@diabetes.org" folder="Physical|American Diabetes Association" saveAttachments="false"/> <EmailRule address="@membership.webshots.com" folder="Social|Webshots" saveAttachments="false"/> </Parse> </TargetPST> </EmailRuleList> Now, I have both an FromAddress and a ToAddress that is parsed from an incoming email. I would like to do a LINQ query against a class set that was deserialized from this XML. For instance: ToAddress = [email protected] FromAddress = [email protected] Query: Get EmailRule.Include(Parse).Include(TargetPST) where address == ToAddress AND Parse.ToAddress==true AND Parse.useJustDomain==false Get EmailRule.Include(Parse).Include(TargetPST) where address == [ToAddress Domain Only] AND Parse.ToAddress==true AND Parse.useJustDomain==true Get EmailRule.Include(Parse).Include(TargetPST) where address == FromAddress AND Parse.FromAddress==true AND Parse.useJustDomain==false Get EmailRule.Include(Parse).Include(TargetPST) where address == [FromAddress Domain Only] AND Parse.FromAddress==true AND Parse.useJustDomain==true I am having a hard time figuring this LINQ query out. I can, of course, loop on all the bits in the XML like so (includes deserialization into objects): XmlSerializer s = new XmlSerializer(typeof(EmailRuleList)); TextReader r = new StreamReader(path); _emailRuleList = (EmailRuleList)s.Deserialize(r); TargetPST[] PSTList = _emailRuleList.Items; foreach (TargetPST targetPST in PSTList) { olRoot = GetRootFolder(targetPST.name); if (olRoot != null) { Parse[] ParseList = targetPST.Items; foreach (Parse parseRules in ParseList) { EmailRule[] EmailRuleList = parseRules.Items; foreach (EmailRule targetFolders in EmailRuleList) { } } } } However, this means going through all these loops for each and every address. It makes more sense to me to query against the Objects. Any tips appreciated!

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• linq query - The method or operation is not implemented.

  - by Dejan.S

  I'm doing the Rob Conery mvc storefront and at one place I'm suppose to get categories but I get an error with this linq query and I can not get why. It's exactly the same as his. var culturedName = from ct in ReadOnlyContext.CategoryCultureDetails where ct.Culture.LanguageCode == System.Globalization.CultureInfo.CurrentUICulture.TwoLetterISOLanguageName select new { ct.CategoryName, ct.CategoryId }; return from c in ReadOnlyContext.Categories join cn in culturedName on c.CategoryId equals cn.CategoryId select new Core.Model.Category { Id = c.CategoryId, Name = cn.CategoryName, ParentId = c.ParentId ?? 0, Products = new LazyList<Core.Model.Product>(from p in GetProducts() join cp in ReadOnlyContext.Categories_Products on p.Id equals cp.ProductId where cp.CategoryId == c.CategoryId select p) }; its the return query that mess things up. I have checked and the culturename actually gets data from the database. Appricate your help

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• ASP.NET MVC <OutputCache> SqlDependency (CommandNotification?) with LINQ queries

  - by sinni800

  Hello, I use LINQ queries in my ASP.NET MVC application and want to use OutputCache in some of my Actions. I hear this should be possible with CommandNotifications. But those seem to only go for self-created SQLCommands, or am I wrong? Can I manually tell SQL server to send SQLDependency notifications if certain tables change? And if yes, how can I attach them to the OutputCache? Another side question: Can you do this with strongly types views too? Thank you in advance...

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• How dynamic can I make my LINQ To SQL Statements?

  - by mcass20

  I have the need to construct a LINQ To SQL statement at runtime based on input from a user and I can't seem to figure out how to dynamically build the WHERE clause. I have no problem with the following: string Filters = "<value>FOO</value>"; Where("FormattedMessage.Contains(@0)",Filters) But what I really need is to make the entire WHERE clause dynamic. This way I can add multiple conditions at runtime like this (rough idea): foreach (Filter filter in filterlist) { whereclause = whereclause + "&& formattedmessage.contains(filter)"; }

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• Using LINQ to XML, how can I join two sets of data based on ordinal position?

  - by Donald Hughes

  Using LINQ to XML, how can I join two sets of data based on ordinal position? <document> <set1> <value>A</value> <value>B</value> <value>C</value> </set1> <set2> <value>1</value> <value>2</value> <value>3</value> </set2> </document> Based on the above fragment, I would like to join the two sets together such that "A" and "1" are in the same record, "B" and "2" are in the same record, and "C" and "3" are in the same record.

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• linq to xml. read. and assign to ViewData..noob

  - by raklos

  I have some xml similar to this: <?xml version="1.0" encoding="utf-8" ?> <data> <resources> <resource key="Title">Alpha</resource> <resource key="ImageName">Small.png</resource> <resource key="Desc">blah</resource> </resources> </data> using linq-xml how can i assign each resource here as a key value pair with the ViewData collection. Thanks.

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• LINQ-to-XML to DataGridView: Cannot edit fields -- How to fix?

  - by Pretzel

  I am currently doing LINQ-to-XML and populating a DataGridView with my query just fine. The trouble I am running into is that once loaded into the DataGridView, the values appear to be Un-editable (ReadOnly). Here's my code: var barcodes = (from src in xmldoc.Descendants("Container") where src.Descendants().Count() > 0 select new { Id = (string)src.Element("Id"), Barcode = (string)src.Element("Barcode"), Quantity = float.Parse((string)src.Element("Quantity").Attribute("value")) }).Distinct(); dataGridView1.DataSource = barcodes.ToList(); I read somewhere that the "DataGridView will be in ReadOnly mode when you use Anonymous types." But I couldn't find an explanation why or exactly what to do about it. Any ideas?

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• How to get List of results from list of ID values with LINQ to SQL?

  - by DaveDev

  I have a list of ID values: List<int> MyIDs { get; set; } I'd like to pass this list to an interface to my repository and have it return a List that match the ID values I pass in. List<MyType> myTypes = new List<MyType>(); IMyRepository myRepos = new SqlMyRepository(); myTypes = myRepos.GetMyTypes(this.MyIDs); Currently, GetMyTypes() behaves similarly to this: public MyType GetMyTypes(int id) { return (from myType in db.MyTypes where myType.Id == id select new MyType { MyValue = myType.MyValue }).FirstOrDefault(); } where I iterate through MyIDs and pass each id in and add each result to a list. How do I need to change the LINQ so that I can pass in the full list of MyIDs and get a list of MyTypes out? GetMyTypes() would have a signature similar to public List<MyType> GetMyTypes(List<int> myIds)

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• Differences between query using LINQ and IQueryable interface directly?

  - by JohnMetta

  Using Entity Framework 4, and given: ObjectSet<Thing> AllThings = Context.CreateObjectSet<Thing>; public IQueryable<Thing> ByNameA(String name) { IQueryable<Thing> query = from o in AllThings where o.Name == name select o; return query; } public IQueryable<Thing> ByNameB(String name) { return AllThings.Where((o) => o.Name == name); } Both return IQueryable< instances, and thus the query doesn't hit the server until something like ToList() is called, right? Is it purely readability that is the difference, or are the using fundamentally different technologies on the back-end?

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• Extending LINQ classes to my own partial classes in different namespaces?

  - by sah302

  I have a .dbml file which of course contains the auto-generated classes based on my tables. I would however, like to extend them to my own classes. Typically I design such that each of my tables get their own namespace in their own folder containing all of their associated dao and service classes. So if I am dealing with a page that only has to do with 'customers' for instance, I can only include the customerNS. But when using LINQ I seem to be unable to do this. I have tried removing a default namespace from the project, I have tried putting the .dbml file into it's own folder with a custom namespace and then adding a 'using' statement, but no nothing works. I also saw the Entity Namespace, Context Namespace, and Custom Tool Namespace properties associated with the .dbml file and tried setting all these to names x and trying 'using x' in my other class to allow me to extend partial classes, but it just doesn't work. Is this possible or do I have to keep all extended partial classes in the same namespace as the .dbml file?

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• How can I load class's part using linq to sql without anonymous class or additional class?

  - by ais

  class Test { int Id{get;set;} string Name {get;set;} string Description {get;set;} } //1)ok context.Tests.Select(t => new {t.Id, t.Name}).ToList().Select(t => new Test{Id = t.Id, Name = t.Name}); //2)ok class TestPart{ int Id{get;set;} string Name {get;set;} } context.Tests.Select(t => new TestPart{Id = t.Id, Name = t.Name}).ToList().Select(t => new Test{Id = t.Id, Name = t.Name}); //3)error Explicit construction of entity type 'Test' in query is not allowed. context.Tests.Select(t => new Test{Id = t.Id, Name = t.Name}).ToList(); Is there any way to use third variant?

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• How can I use linq to build an object from 1 row of data?

  - by Hcabnettek

  Hi All, I have a quick linq question. I have a stored proc that should return one row of data. I would like to use a lambda to build an object. Here's what I'm currently doing which works, but I know I should be able to use First instead of Select except I can't seem to get the syntax correct. Can anyone straighten me out here? Thanks for any help. var location = new GeoLocationDC(); DataSet ds = db.ExecuteDataSet(dbCommand); if(ds.Tables[0].Rows.Count == 1) { var rows = ds.Tables[0].AsEnumerable(); var x = rows.Select( c => new GeoLocationDC { Latitude = Convert.ToInt32(c.Field<string>("LATITUDE")), Longitude = Convert.ToInt32(c.Field<string>("LONGITUDE")) }).ToList(); if(x.Count > 0 ) { location = x[0]; } Cheers, ~ck }

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• LINQ to SQL for tables across databases. Or View?

  - by BritishDeveloper

  I have a Message table and a User table. Both are in separate databases. There is a userID in the Message table that is used to join to the User table to find things like userName. How can I create this in LINQ to SQL? I can't seem to do a cross database join. Should I create a View in the database and use that instead? Will that work? What will happen to CRUD against it? E.g. if I delete a message - surely it won't delete the user? I'd imagine it would throw an error. What to do? I can't move the tables into the same database!

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• Using Linq, how to separate a list in to grouped objects by name?

  - by Dr. Zim

  I have a table where a record looks like this varchar(255) Name varchar(255) Text varchar(255) Value Name is the DDL name, Text is what is displayed, and Value is returned upon selection. There are between one and twenty options for each Name. Without iterating though each option like a cursor, is there any way to pull out a list of objects, one for each unique DDL Name, using Linq and C#? A sample of the data: Beds '4 (10)' 4 Beds '5 (1)' 5 Beds '7 (1)' 7 Baths 'NA (13)' NULL Baths '0 (1)' 0 Baths '1 (13)' 1 I was thinking about doing an outer select to get the unique Names, then an inner select to get the list of options for it, then return the set as a List of a set of Lists.

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• LINQ query for tag system: Matching any of several tags?

  - by David Veeneman

  I am just getting started with LINQ. I am creating an Entity Framework app that uses the canonical Post and Tag model. A Post contains an ID, Text, and Tags, and a Tag contains an ID, a Name, and Posts. A previous thread on StackOverflow showed me how to query for a Post that matches all Tag objects (A and B and C) in a search list. But how would I query for a Post that matches any Tag (A or B or C) in the list? Thanks for your help.

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• Global Entity Framework Context in WPF Application

  - by OffApps Cory

  Good day, I am in the middle of development of a WPF application that is using Entity Framework (.NET 3.5). It accesses the entities in several places throughout. I am worried about consistency throughout the application in regard to the entities. Should I be instancing separate contexts in my different views, or should I (and is a a good way to do this) instance a single context that can be accessed globally? For instance, my entity model has three sections, Shipments (with child packages and further child contents), Companies/Contacts (with child addresses and telephones), and disk specs. The Shipments and EditShipment views access the DiskSpecs, and the OptionsView manages the DiskSpecs (Create, Edit, Delete). If I edit a DiskSpec, I have to have something in the ShipmentsView to retrieve the latest specs if I have separate contexts right? If it is safe to have one overall context from which the rest of the app retrieves it's objects, then I imagine that is the way to go. If so, where would that instance be put? I am using VB.NET, but I can translate from C# pretty good. Any help would be appreciated. I just don't want one of those applications where the user has to hit reload a dozen times in different parts of the app to get the new data. Update: OK so I have changed my app as follows: All contexts are created in Using Blocks to dispose of them after they are no longer needed. When loaded, all entities are detatched from context before it is disposed. A new property in the MainViewModel (ContextUpdated) raises an event that all of the other ViewModels subscribe to which runs that ViewModels RefreshEntities method. After implementing this, I started getting errors saying that an entity can only be referenced by one ChangeTracker at a time. Since I could not figure out which context was still referencing the entity (shouldn't be any context right?) I cast the object as IEntityWithChangeTracker, and set SetChangeTracker to nothing (Null). This has let to the current problem: When I Null the changeTracker on the Entity, and then attach it to a context, it loses it's changed state and does not get updated to the database. However if I do not null the change tracker, I can't attach. I have my own change tracking code, so that is not a problem. My new question is, how are you supposed to do this. A good example Entity query and entity save code snipped would go a long way, cause I am beating my head in trying to get what I once thought was a simple transaction to work. Any help would elevate you to near god-hood.

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• Generating EF Code First model classes from an existing database

  - by Jon Galloway

  Entity Framework Code First is a lightweight way to "turn on" data access for a simple CLR class. As the name implies, the intended use is that you're writing the code first and thinking about the database later. However, I really like the Entity Framework Code First works, and I want to use it in existing projects and projects with pre-existing databases. For example, MVC Music Store comes with a SQL Express database that's pre-loaded with a catalog of music (including genres, artists, and songs), and while it may eventually make sense to load that seed data from a different source, for the MVC 3 release we wanted to keep using the existing database. While I'm not getting the full benefit of Code First - writing code which drives the database schema - I can still benefit from the simplicity of the lightweight code approach. Scott Guthrie blogged about how to use entity framework with an existing database, looking at how you can override the Entity Framework Code First conventions so that it can work with a database which was created following other conventions. That gives you the information you need to create the model classes manually. However, it turns out that with Entity Framework 4 CTP 5, there's a way to generate the model classes from the database schema. Once the grunt work is done, of course, you can go in and modify the model classes as you'd like, but you can save the time and frustration of figuring out things like mapping SQL database types to .NET types. Note that this template requires Entity Framework 4 CTP 5 or later. You can install EF 4 CTP 5 here. Step One: Generate an EF Model from your existing database The code generation system in Entity Framework works from a model. You can add a model to your existing project and delete it when you're done, but I think it's simpler to just spin up a separate project to generate the model classes. When you're done, you can delete the project without affecting your application, or you may choose to keep it around in case you have other database schema updates which require model changes. I chose to add the Model classes to the Models folder of a new MVC 3 application. Right-click the folder and select "Add / New Item..."   Next, select ADO.NET Entity Data Model from the Data Templates list, and name it whatever you want (the name is unimportant).   Next, select "Generate from database." This is important - it's what kicks off the next few steps, which read your database's schema.   Now it's time to point the Entity Data Model Wizard at your existing database. I'll assume you know how to find your database - if not, I covered that a bit in the MVC Music Store tutorial section on Models and Data. Select your database, uncheck the "Save entity connection settings in Web.config" (since we won't be using them within the application), and click Next.   Now you can select the database objects you'd like modeled. I just selected all tables and clicked Finish.   And there's your model. If you want, you can make additional changes here before going on to generate the code.   Step Two: Add the DbContext Generator Like most code generation systems in Visual Studio lately, Entity Framework uses T4 templates which allow for some control over how the code is generated. K Scott Allen wrote a detailed article on T4 Templates and the Entity Framework on MSDN recently, if you'd like to know more. Fortunately for us, there's already a template that does just what we need without any customization. Right-click a blank space in the Entity Framework model surface and select "Add Code Generation Item..." Select the Code groupt in the Installed Templates section and pick the ADO.NET DbContext Generator. If you don't see this listed, make sure you've got EF 4 CTP 5 installed and that you're looking at the Code templates group. Note that the DbContext Generator template is similar to the EF POCO template which came out last year, but with "fix up" code (unnecessary in EF Code First) removed.   As soon as you do this, you'll two terrifying Security Warnings - unless you click the "Do not show this message again" checkbox the first time. It will also be displayed (twice) every time you rebuild the project, so I checked the box and no immediate harm befell my computer (fingers crossed!).   Here's the payoff: two templates (filenames ending with .tt) have been added to the project, and they've generated the code I needed.   The "MusicStoreEntities.Context.tt" template built a DbContext class which holds the entity collections, and the "MusicStoreEntities.tt" template build a separate class for each table I selected earlier. We'll customize them in the next step. I recommend copying all the generated .cs files into your application at this point, since accidentally rebuilding the generation project will overwrite your changes if you leave them there. Step Three: Modify and use your POCO entity classes Note: I made a bunch of tweaks to my POCO classes after they were generated. You don't have to do any of this, but I think it's important that you can - they're your classes, and EF Code First respects that. Modify them as you need for your application, or don't. The Context class derives from DbContext, which is what turns on the EF Code First features. It holds a DbSet for each entity. Think of DbSet as a simple List, but with Entity Framework features turned on.   //------------------------------------------------------------------------------ // <auto-generated> // This code was generated from a template. // // Changes to this file may cause incorrect behavior and will be lost if // the code is regenerated. // </auto-generated> //------------------------------------------------------------------------------ namespace EF_CodeFirst_From_Existing_Database.Models { using System; using System.Data.Entity; public partial class Entities : DbContext { public Entities() : base("name=Entities") { } public DbSet<Album> Albums { get; set; } public DbSet<Artist> Artists { get; set; } public DbSet<Cart> Carts { get; set; } public DbSet<Genre> Genres { get; set; } public DbSet<OrderDetail> OrderDetails { get; set; } public DbSet<Order> Orders { get; set; } } } It's a pretty lightweight class as generated, so I just took out the comments, set the namespace, removed the constructor, and formatted it a bit. Done. If I wanted, though, I could have added or removed DbSets, overridden conventions, etc. using System.Data.Entity; namespace MvcMusicStore.Models { public class MusicStoreEntities : DbContext { public DbSet Albums { get; set; } public DbSet Genres { get; set; } public DbSet Artists { get; set; } public DbSet Carts { get; set; } public DbSet Orders { get; set; } public DbSet OrderDetails { get; set; } } } Next, it's time to look at the individual classes. Some of mine were pretty simple - for the Cart class, I just need to remove the header and clean up the namespace. //------------------------------------------------------------------------------ // // This code was generated from a template. // // Changes to this file may cause incorrect behavior and will be lost if // the code is regenerated. // //------------------------------------------------------------------------------ namespace EF_CodeFirst_From_Existing_Database.Models { using System; using System.Collections.Generic; public partial class Cart { // Primitive properties public int RecordId { get; set; } public string CartId { get; set; } public int AlbumId { get; set; } public int Count { get; set; } public System.DateTime DateCreated { get; set; } // Navigation properties public virtual Album Album { get; set; } } } I did a bit more customization on the Album class. Here's what was generated: //------------------------------------------------------------------------------ // // This code was generated from a template. // // Changes to this file may cause incorrect behavior and will be lost if // the code is regenerated. // //------------------------------------------------------------------------------ namespace EF_CodeFirst_From_Existing_Database.Models { using System; using System.Collections.Generic; public partial class Album { public Album() { this.Carts = new HashSet(); this.OrderDetails = new HashSet(); } // Primitive properties public int AlbumId { get; set; } public int GenreId { get; set; } public int ArtistId { get; set; } public string Title { get; set; } public decimal Price { get; set; } public string AlbumArtUrl { get; set; } // Navigation properties public virtual Artist Artist { get; set; } public virtual Genre Genre { get; set; } public virtual ICollection Carts { get; set; } public virtual ICollection OrderDetails { get; set; } } } I removed the header, changed the namespace, and removed some of the navigation properties. One nice thing about EF Code First is that you don't have to have a property for each database column or foreign key. In the Music Store sample, for instance, we build the app up using code first and start with just a few columns, adding in fields and navigation properties as the application needs them. EF Code First handles the columsn we've told it about and doesn't complain about the others. Here's the basic class: using System.ComponentModel; using System.ComponentModel.DataAnnotations; using System.Web.Mvc; using System.Collections.Generic; namespace MvcMusicStore.Models { public class Album { public int AlbumId { get; set; } public int GenreId { get; set; } public int ArtistId { get; set; } public string Title { get; set; } public decimal Price { get; set; } public string AlbumArtUrl { get; set; } public virtual Genre Genre { get; set; } public virtual Artist Artist { get; set; } public virtual List OrderDetails { get; set; } } } It's my class, not Entity Framework's, so I'm free to do what I want with it. I added a bunch of MVC 3 annotations for scaffolding and validation support, as shown below: using System.ComponentModel; using System.ComponentModel.DataAnnotations; using System.Web.Mvc; using System.Collections.Generic; namespace MvcMusicStore.Models { [Bind(Exclude = "AlbumId")] public class Album { [ScaffoldColumn(false)] public int AlbumId { get; set; } [DisplayName("Genre")] public int GenreId { get; set; } [DisplayName("Artist")] public int ArtistId { get; set; } [Required(ErrorMessage = "An Album Title is required")] [StringLength(160)] public string Title { get; set; } [Required(ErrorMessage = "Price is required")] [Range(0.01, 100.00, ErrorMessage = "Price must be between 0.01 and 100.00")] public decimal Price { get; set; } [DisplayName("Album Art URL")] [StringLength(1024)] public string AlbumArtUrl { get; set; } public virtual Genre Genre { get; set; } public virtual Artist Artist { get; set; } public virtual List<OrderDetail> OrderDetails { get; set; } } } The end result was that I had working EF Code First model code for the finished application. You can follow along through the tutorial to see how I built up to the finished model classes, starting with simple 2-3 property classes and building up to the full working schema. Thanks to Diego Vega (on the Entity Framework team) for pointing me to the DbContext template.

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• LLBLGen Pro feature highlights: grouping model elements

  - by FransBouma

  (This post is part of a series of posts about features of the LLBLGen Pro system) When working with an entity model which has more than a few entities, it's often convenient to be able to group entities together if they belong to a semantic sub-model. For example, if your entity model has several entities which are about 'security', it would be practical to group them together under the 'security' moniker. This way, you could easily find them back, yet they can be left inside the complete entity model altogether so their relationships with entities outside the group are kept. In other situations your domain consists of semi-separate entity models which all target tables/views which are located in the same database. It then might be convenient to have a single project to manage the complete target database, yet have the entity models separate of each other and have them result in separate code bases. LLBLGen Pro can do both for you. This blog post will illustrate both situations. The feature is called group usage and is controllable through the project settings. This setting is supported on all supported O/R mapper frameworks. Situation one: grouping entities in a single model. This situation is common for entity models which are dense, so many relationships exist between all sub-models: you can't split them up easily into separate models (nor do you likely want to), however it's convenient to have them grouped together into groups inside the entity model at the project level. A typical example for this is the AdventureWorks example database for SQL Server. This database, which is a single catalog, has for each sub-group a schema, however most of these schemas are tightly connected with each other: adding all schemas together will give a model with entities which indirectly are related to all other entities. LLBLGen Pro's default setting for group usage is AsVisualGroupingMechanism which is what this situation is all about: we group the elements for visual purposes, it has no real meaning for the model nor the code generated. Let's reverse engineer AdventureWorks to an entity model. By default, LLBLGen Pro uses the target schema an element is in which is being reverse engineered, as the group it will be in. This is convenient if you already have categorized tables/views in schemas, like which is the case in AdventureWorks. Of course this can be switched off, or corrected on the fly. When reverse engineering, we'll walk through a wizard which will guide us with the selection of the elements which relational model data should be retrieved, which we can later on use to reverse engineer to an entity model. The first step after specifying which database server connect to is to select these elements. below we can see the AdventureWorks catalog as well as the different schemas it contains. We'll include all of them. After the wizard completes, we have all relational model data nicely in our catalog data, with schemas. So let's reverse engineer entities from the tables in these schemas. We select in the catalog explorer the schemas 'HumanResources', 'Person', 'Production', 'Purchasing' and 'Sales', then right-click one of them and from the context menu, we select Reverse engineer Tables to Entity Definitions.... This will bring up the dialog below. We check all checkboxes in one go by checking the checkbox at the top to mark them all to be added to the project. As you can see LLBLGen Pro has already filled in the group name based on the schema name, as this is the default and we didn't change the setting. If you want, you can select multiple rows at once and set the group name to something else using the controls on the dialog. We're fine with the group names chosen so we'll simply click Add to Project. This gives the following result:   (I collapsed the other groups to keep the picture small ;)). As you can see, the entities are now grouped. Just to see how dense this model is, I've expanded the relationships of Employee: As you can see, it has relationships with entities from three other groups than HumanResources. It's not doable to cut up this project into sub-models without duplicating the Employee entity in all those groups, so this model is better suited to be used as a single model resulting in a single code base, however it benefits greatly from having its entities grouped into separate groups at the project level, to make work done on the model easier. Now let's look at another situation, namely where we work with a single database while we want to have multiple models and for each model a separate code base. Situation two: grouping entities in separate models within the same project. To get rid of the entities to see the second situation in action, simply undo the reverse engineering action in the project. We still have the AdventureWorks relational model data in the catalog. To switch LLBLGen Pro to see each group in the project as a separate project, open the Project Settings, navigate to General and set Group usage to AsSeparateProjects. In the catalog explorer, select Person and Production, right-click them and select again Reverse engineer Tables to Entities.... Again check the checkbox at the top to mark all entities to be added and click Add to Project. We get two groups, as expected, however this time the groups are seen as separate projects. This means that the validation logic inside LLBLGen Pro will see it as an error if there's e.g. a relationship or an inheritance edge linking two groups together, as that would lead to a cyclic reference in the code bases. To see this variant of the grouping feature, seeing the groups as separate projects, in action, we'll generate code from the project with the two groups we just created: select from the main menu: Project -> Generate Source-code... (or press F7 ;)). In the dialog popping up, select the target .NET framework you want to use, the template preset, fill in a destination folder and click Start Generator (normal). This will start the code generator process. As expected the code generator has simply generated two code bases, one for Person and one for Production: The group name is used inside the namespace for the different elements. This allows you to add both code bases to a single solution and use them together in a different project without problems. Below is a snippet from the code file of a generated entity class. //... using System.Xml.Serialization; using AdventureWorks.Person; using AdventureWorks.Person.HelperClasses; using AdventureWorks.Person.FactoryClasses; using AdventureWorks.Person.RelationClasses; using SD.LLBLGen.Pro.ORMSupportClasses; namespace AdventureWorks.Person.EntityClasses { //... /// <summary>Entity class which represents the entity 'Address'.<br/><br/></summary> [Serializable] public partial class AddressEntity : CommonEntityBase //... The advantage of this is that you can have two code bases and work with them separately, yet have a single target database and maintain everything in a single location. If you decide to move to a single code base, you can do so with a change of one setting. It's also useful if you want to keep the groups as separate models (and code bases) yet want to add relationships to elements from another group using a copy of the entity: you can simply reverse engineer the target table to a new entity into a different group, effectively making a copy of the entity. As there's a single target database, changes made to that database are reflected in both models which makes maintenance easier than when you'd have a separate project for each group, with its own relational model data. Conclusion LLBLGen Pro offers a flexible way to work with entities in sub-models and control how the sub-models end up in the generated code.

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• Adding sub-entities to existing entities. Should it be done in the Entity and Component classes?

  - by Coyote

  I'm in a situation where a player can be given the control of small parts of an entity (i.e. Left missile battery). Therefore I started implementing sub entities as follow. Entities are Objects with 3 arrays: pointers to components pointers to sub entities communication subscribers (temporary implementation) Now when an entity is built it has a few components as you might expect and also I can attach sub entities which are handled with some dedicated code in the Entity and Component classes. I noticed sub entities are sharing data in 3 parts: position: the sub entities are using the parent's position and their own as an offset. scrips: sub entities are draining ammo and energy from the parent. physics: sub entities add weight to the parent I made this to quickly go forward, but as I'm slowly fixing current implementations I wonder if this wasn't a mistake. Is my current implementation something commonly done? Will this implementation put me in a corner? I thought it might be a better thing to create some sort of SubEntityComponent where sub entities are attached and handled. But before changing anything I wanted to seek the community's wisdom.

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• How to get rank from full-text search query with Linq to SQL?

  - by Stephen Jennings

  I am using Linq to SQL to call a stored procedure which runs a full-text search and returns the rank plus a few specific columns from the table Article. The rank column is the rank returned from the SQL function FREETEXTTABLE(). I've added this sproc to the data model designer with return type Article. This is working to get the columns I need; however, it discards the ranking of each search result. I'd like to get this information so I can display it to the user. So far, I've tried creating a new class RankedArticle which inherits from Article and adds the column Rank, then changing the return type of my sproc mapping to RankedArticle. When I try this, an InvalidOperationException gets thrown: Data member 'Int32 ArticleID' of type 'Heap.Models.Article' is not part of the mapping for type 'RankedArticle'. Is the member above the root of an inheritance hierarchy? I can't seem to find any other questions or Google results from people trying to get the rank column, so I'm probably missing something obvious here.

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• Linq-to-sql Compiled Query returns object NOT belonging to submitted DataContext ?

  - by Vladimir Kojic

  Compiled query: public static class Machines { public static readonly Func<OperationalDataContext, short, Machine> QueryMachineById = CompiledQuery.Compile((OperationalDataContext db, short machineID) => db.Machines.Where(m => m.MachineID == machineID).SingleOrDefault() ); public static Machine GetMachineById(IUnitOfWork unitOfWork, short id) { Machine machine; // Old code (working) //var machineRepository = unitOfWork.GetRepository<Machine>(); //machine = machineRepository.Find(m => m.MachineID == id).SingleOrDefault(); // New code (making problems) machine = QueryMachineById(unitOfWork.DataContext, id); return machine; } It looks like compiled query is returning result from another data context [TestMethod] public void GetMachinesTest() { using (var unitOfWork = IoC.Get<IUnitOfWork>()) { // Compile Query var machine = Machines.GetMachineById(unitOfWork, 3); } using (var unitOfWork = IoC.Get<IUnitOfWork>()) { var machineRepository = unitOfWork.GetRepository<Machine>(); // Get From Repository var machineFromRepository = machineRepository.Find(m => m.MachineID == 2).SingleOrDefault(); var machine = Machines.GetMachineById(unitOfWork, 2); VerifyHuskyHostMachine(machineFromRepository, 2, "Machine 2", "222222", "H400RS", "MachineIconB.xaml", false, true, LicenseType.Licensed, InterfaceType.HuskyHostV2, "10.0.97.2:8080", "10.0.97.2", 8080, "4.0"); VerifyHuskyHostMachine(machine, 2, "Machine 2", "222222", "H400RS", "MachineIconB.xaml", false, true, LicenseType.Licensed, InterfaceType.HuskyHostV2, "10.0.97.2:8080", "10.0.97.2", 8080, "4.0"); Assert.AreSame(machineFromRepository, machine); // FAIL } } If I run other (complex) unit tests I'm getting as expected: An attempt has been made to Attach or Add an entity that is not new, perhaps having been loaded from another DataContext. Another Important information is that this test is under TransactionScope! UPDATE: It looks like next link is describing similar problem (is this bug solved ?): http://social.msdn.microsoft.com/Forums/en-US/linqprojectgeneral/thread/9bcffc2d-794e-4c4a-9e3e-cdc89dad0e38

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• ASP.NET MVC 2: How to write this Linq SQL as a Dynamic Query (using strings)?

  - by Dr. Zim

  Skip to the "specific question" as needed. Some background: The scenario: I have a set of products with a "drill down" filter (Query Object) populated with DDLs. Each progressive DDL selection will further limit the product list as well as what options are left for the DDLs. For example, selecting a hammer out of tools limits the Product Sizes to only show hammer sizes. Current setup: I created a query object, sent it to a repository, and fed each option to a SQL "table valued function" where null values represent "get all products". I consider this a good effort, but far from DDD acceptable. I want to avoid any "programming" in SQL, hopefully doing everything with a repository. Comments on this topic would be appreciated. Specific question: How would I rewrite this query as a Dynamic Query? A link to something like 101 Linq Examples would be fantastic, but with a Dynamic Query scope. I really want to pass to this method the field in quotes "" for which I want a list of options and how many products have that option. (from p in db.Products group p by p.ProductSize into g select new Category { PropertyType = g.Key, Count = g.Count() }).Distinct(); Each DDL option will have "The selection (21)" where the (21) is the quantity of products that have that attribute. Upon selecting an option, all other remaining DDLs will update with the remaining options and counts.

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• Can LINQ expression classes implement the observer pattern instead of deferred execution?

  - by Tormod

  Hi. We have issues within an application using a state machine. The application is implemented as a windows service and is iteration based (it "foreaches" itself through everything) and there are myriads of instances being processed by the state machine. As I'm reading the MEAP version of Jon Skeets book "C# in Depth, 2nd ed", I'm wondering if I can change the whole thing to use linq expression instances so that guards and conditions are represented using expression trees. We are building many applications on this state machine engine and would probably greatly benefit from the new Expression tree visualizer in VS 2010 Now, simple example. If I have an expression tree where there is an OR Expression condition with two sub nodes, is there any way that these can implement the observer pattern so that the expression tree becomes event driven? If a condition change, it should notify its parent node (the OR node). Since the OR node then changes from "false" to "true", then it should notify ITS parent and so on. I love the declarative model of expression trees, but the deferred execution model works in opposite direction of the control flow if you want event based "live" conditions. Am I off on a wild goose chase here? Or is there some concept in the BCL that may help me achieve this?

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• LINQ to SQL - How to efficiently do either an AND or an OR search for multiple criteria

  - by Dan Diplo

  I have an ASP.NET MVC site (which uses Linq To Sql for the ORM) and a situation where a client wants a search facility against a bespoke database whereby they can choose to either do an 'AND' search (all criteria match) or an 'OR' search (any criteria match). The query is quite complex and long and I want to know if there is a simple way I can make it do both without having to have create and maintain two different versions of the query. For instance, the current 'AND' search looks something like this (but this is a much simplified version): private IQueryable<SampleListDto> GetSampleSearchQuery(SamplesCriteria criteria) { var results = from r in Table where (r.Id == criteria.SampleId) && (r.Status.SampleStatusId == criteria.SampleStatusId) && (r.Job.JobNumber.StartsWith(criteria.JobNumber)) && (r.Description.Contains(criteria.Description)) select r; } I could copy this and replace the && with || operators to get the 'OR' version, but feel there must be a better way of achieving this. Does anybody have any suggestions how this can be achieved in an efficient and flexible way that is easy to maintain? Thanks.

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• [C#]How to introduce retry logic into LINQ to SQL to deal with timeouts?

  - by codemonkie

  I need to find ways to add retry mechanism to my DB calls in case of timeouts, LINQ to SQL is used to call some sprocs in my code... using (MyDataContext dc = new MyDataContext()) { int result = -1; //denote failure int count = 0; while ((result < 0) && (count < MAX_RETRIES)) { result = dc.myStoredProc1(...); count++; } result = -1; count = 0; while ((result < 0) && (count < MAX_RETRIES)) { result = dc.myStoredProc2(...); count++; } ... ... } Not sure if the code above is right or posed any complications. It'll be nice to throw an exception after MAX_RETRIES has reached, but I dunno how and where to throw them appropriately :-) Any helps appreciated.

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