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• 'Generic' ViewModel

  - by Ian MacPherson

  Using EF 4, I have several subtypes of a 'Business' entity (customers, suppliers, haulage companies etc). They DO need to be subtypes. I am building a general viewmodel which calls into a service from which a generic repository is accessed. As I have 4 subtypes, it would be good to have a 'generic' viewmodel used for all of these. Problem is of course is that I have to call a specific type into my generic repository, for example: BusinessToRetrieve = _repository .LoadEntity<Customer>(o => o.CustomerID == customerID); It would be good to be able to call <SomethingElse>, somethingElse being one or other of the subtypes), otherwise I shall have to create 4 near identical viemodels, which seems a waste of course! The subtype entity name is available to the viewmodel but I've been unable to figure out how to make the above call convert this into a type. An issue with achieving what I want is that presumably the lambda expression being passed in wouldn't be able to resolve on a 'generic' call ?

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• ASP.net MVC 2.0 using the same form for adding and editing.

  - by Chevex

  I would like to use the same view for editing a blog post and adding a blog post. However, I'm having an issue with the ID. When adding a blog post, I have no need for an ID value to be posted. When model binding binds the form values to the BlogPost object in the controller, it will auto-generate the ID in entity framework entity. When I am editing a blog post I DO need a hidden form field to store the ID in so that it accompanies the next form post. Here is the view I have right now. <% using (Html.BeginForm("CommitEditBlogPost", "Admin")) { %> <% if (Model != null) { %> <%: Html.HiddenFor(x => x.Id)%> <% } %> Title:<br /> <%: Html.TextBoxFor(x => x.Title, new { Style = "Width: 90%;" })%> <br /> <br /> Summary:<br /> <%: Html.TextAreaFor(x => x.Summary, new { Style = "Width: 90%; Height: 50px;" }) %> <br /> <br /> Body:<br /> <%: Html.TextAreaFor(x => x.Body, new { Style = "Height: 250px; Width: 90%;" })%> <br /> <br /> <input type="submit" value="Submit" /> <% } %> Right now checking if the model is coming in NULL is a great way to know if I'm editing a blog post or adding one, because when I'm adding one it will be null as it hasn't been created yet. The problem comes in when there is an error and the entity is invalid. When the controller renders the form after an invalid model the Model != null evaluates to false, even though we are editing a post and there is clearly a model. If I render the hidden input field for ID when adding a post, I get an error stating that the ID can't be null. Any help is appreciated. EDIT: I went with OJ's answer for this question, however I discovered something that made me feel silly and I wanted to share it just in case anyone was having a similar issue. The page the adds/edits blogs does not even need a hidden field for id, ever. The reason is because when I go to add a blog I do a GET to this relative URL BlogProject/Admin/AddBlogPost This URL does not contain an ID and the action method just renders the page. The page does a POST to the same URL when adding the blog post. The incoming BlogPost entity has a null Id and is generated by EF during save changes. The same thing happens when I edit blog posts. The URL is BlogProject/Admin/EditBlogPost/{Id} This URL contains the id of the blog post and since the page is posting back to the exact same URL the id goes with the POST to the action method that executes the edit. The only problem I encountered with this is that the action methods cannot have identical signatures. [HttpGet] public ViewResult EditBlogPost(int Id) { } [HttpPost] public ViewResult EditBlogPost(int Id) { } The compiler will yell at you if you try to use these two methods above. It is far too convenient that the Id will be posted back when doing a Html.BeginForm() with no arguments for action or controller. So rather than change the name of the POST method I just modified the arguments to include a FormCollection. Like this: [HttpPost] public ViewResult EditBlogPost(int Id, FormCollection formCollection) { // You can then use formCollection as the IValueProvider for UpdateModel() // and TryUpdateModel() if you wish. I mean, you might as well use the // argument since you're taking it. } The formCollection variable is filled via model binding with the same content that Request.Form would be by default. You don't have to use this collection for UpdateModel() or TryUpdateModel() but I did just so I didn't feel like that collection was pointless since it really was just to make the method signature different from its GET counterpart. Thanks for the help guys!

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• Entity Framework 5, separating business logic from model - Repository?

  - by bnice7

  I am working on my first public-facing web application and I’m using MVC 4 for the presentation layer and EF 5 for the DAL. The database structure is locked, and there are moderate differences between how the user inputs data and how the database itself gets populated. I have done a ton of reading on the repository pattern (which I have never used) but most of my research is pushing me away from using it since it supposedly creates an unnecessary level of abstraction for the latest versions of EF since repositories and unit-of-work are already built-in. My initial approach is to simply create a separate set of classes for my business objects in the BLL that can act as an intermediary between my Controllers and the DAL. Here’s an example class: public class MyBuilding { public int Id { get; private set; } public string Name { get; set; } public string Notes { get; set; } private readonly Entities _context = new Entities(); // Is this thread safe? private static readonly int UserId = WebSecurity.GetCurrentUser().UserId; public IEnumerable<MyBuilding> GetList() { IEnumerable<MyBuilding> buildingList = from p in _context.BuildingInfo where p.Building.UserProfile.UserId == UserId select new MyBuilding {Id = p.BuildingId, Name = p.BuildingName, Notes = p.Building.Notes}; return buildingList; } public void Create() { var b = new Building {UserId = UserId, Notes = this.Notes}; _context.Building.Add(b); _context.SaveChanges(); // Set the building ID this.Id = b.BuildingId; // Seed 1-to-1 tables with reference the new building _context.BuildingInfo.Add(new BuildingInfo {Building = b}); _context.GeneralInfo.Add(new GeneralInfo {Building = b}); _context.LocationInfo.Add(new LocationInfo {Building = b}); _context.SaveChanges(); } public static MyBuilding Find(int id) { using (var context = new Entities()) // Is this OK to do in a static method? { var b = context.Building.FirstOrDefault(p => p.BuildingId == id && p.UserId == UserId); if (b == null) throw new Exception("Error: Building not found or user does not have access."); return new MyBuilding {Id = b.BuildingId, Name = b.BuildingInfo.BuildingName, Notes = b.Notes}; } } } My primary concern: Is the way I am instantiating my DbContext as a private property thread-safe, and is it safe to have a static method that instantiates a separate DbContext? Or am I approaching this all wrong? I am not opposed to learning up on the repository pattern if I am taking the total wrong approach here.

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• SSIS Lookup component tuning tips

  - by jamiet

  Yesterday evening I attended a London meeting of the UK SQL Server User Group at Microsoft’s offices in London Victoria. As usual it was both a fun and informative evening and in particular there seemed to be a few questions arising about tuning the SSIS Lookup component; I rattled off some comments and figured it would be prudent to drop some of them into a dedicated blog post, hence the one you are reading right now. Scene setting A popular pattern in SSIS is to use a Lookup component to determine whether a record in the pipeline already exists in the intended destination table or not and I cover this pattern in my 2006 blog post Checking if a row exists and if it does, has it changed? (note to self: must rewrite that blog post for SSIS2008). Fundamentally the SSIS lookup component (when using FullCache option) sucks some data out of a database and holds it in memory so that it can be compared to data in the pipeline. One of the big benefits of using SSIS dataflows is that they process data one buffer at a time; that means that not all of the data from your source exists in the dataflow at the same time and is why a SSIS dataflow can process data volumes that far exceed the available memory. However, that only applies to data in the pipeline; for reasons that are hopefully obvious ALL of the data in the lookup set must exist in the memory cache for the duration of the dataflow’s execution which means that any memory used by the lookup cache will not be available to be used as a pipeline buffer. Moreover, there’s an obvious correlation between the amount of data in the lookup cache and the time it takes to charge that cache; the more data you have then the longer it will take to charge and the longer you have to wait until the dataflow actually starts to do anything. For these reasons your goal is simple: ensure that the lookup cache contains as little data as possible. General tips Here is a simple tick list you can follow in order to tune your lookups: Use a SQL statement to charge your cache, don’t just pick a table from the dropdown list made available to you. (Read why in SELECT *... or select from a dropdown in an OLE DB Source component?) Only pick the columns that you need, ignore everything else Make the database columns that your cache is populated from as narrow as possible. If a column is defined as VARCHAR(20) then SSIS will allocate 20 bytes for every value in that column – that is a big waste if the actual values are significantly less than 20 characters in length. Do you need DT_WSTR typed columns or will DT_STR suffice? DT_WSTR uses twice the amount of space to hold values that can be stored using a DT_STR so if you can use DT_STR, consider doing so. Same principle goes for the numerical datatypes DT_I2/DT_I4/DT_I8. Only populate the cache with data that you KNOW you will need. In other words, think about your WHERE clause! Thinking outside the box It is tempting to build a large monolithic dataflow that does many things, one of which is a Lookup. Often though you can make better use of your available resources by, well, mixing things up a little and here are a few ideas to get your creative juices flowing: There is no rule that says everything has to happen in a single dataflow. If you have some particularly resource intensive lookups then consider putting that lookup into a dataflow all of its own and using raw files to pass the pipeline data in and out of that dataflow. Know your data. If you think, for example, that the majority of your incoming rows will match with only a small subset of your lookup data then consider chaining multiple lookup components together; the first would use a FullCache containing that data subset and the remaining data that doesn’t find a match could be passed to a second lookup that perhaps uses a NoCache lookup thus negating the need to pull all of that least-used lookup data into memory. Do you need to process all of your incoming data all at once? If you can process different partitions of your data separately then you can partition your lookup cache as well. For example, if you are using a lookup to convert a location into a [LocationId] then why not process your data one region at a time? This will mean your lookup cache only has to contain data for the location that you are currently processing and with the ability of the Lookup in SSIS2008 and beyond to charge the cache using a dynamically built SQL statement you’ll be able to achieve it using the same dataflow and simply loop over it using a ForEach loop. Taking the previous data partitioning idea further … a dataflow can contain more than one data path so why not split your data using a conditional split component and, again, charge your lookup caches with only the data that they need for that partition. Lookups have two uses: to (1) find a matching row from the lookup set and (2) put attributes from that matching row into the pipeline. Ask yourself, do you need to do these two things at the same time? After all once you have the key column(s) from your lookup set then you can use that key to get the rest of attributes further downstream, perhaps even in another dataflow. Are you using the same lookup data set multiple times? If so, consider the file caching option in SSIS 2008 and beyond. Above all, experiment and be creative with different combinations. You may be surprised at what works. Final  thoughts If you want to know more about how the Lookup component differs in SSIS2008 from SSIS2005 then I have a dedicated blog post about that at Lookup component gets a makeover. I am on a mini-crusade at the moment to get a BULK MERGE feature into the database engine, the thinking being that if the database engine can quickly merge massive amounts of data in a similar manner to how it can insert massive amounts using BULK INSERT then that’s a lot of work that wouldn’t have to be done in the SSIS pipeline. If you think that is a good idea then go and vote for BULK MERGE on Connect. If you have any other tips to share then please stick them in the comments. Hope this helps! @Jamiet Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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• How-to tell the ViewCriteria a user chose in an af:query component

  - by frank.nimphius

  Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} The af:query component defines a search form for application users to enter search conditions for a selected View Criteria. A View Criteria is a named where clauses that you can create declaratively on the ADF Business Component View Object. A default View Criteria that allows users to search in all attributes exists by default and exposed in the Data Controls panel. To create an ADF Faces search form, expand the View Object node that contains the View Criteria definition in the Data Controls panel. Drag the View Criteria that should be displayed as the default criteria onto the page and choose Query in the opened context menu. One of the options within the Query option is to create an ADF Query Panel with Table, which displays the result set in a table view, which can have additional column filters defined. Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} To intercept the user query for modification, or just to know about the selected View Criteria, you override the QueryListener property on the af:query component of the af:table component. Overriding the QueryListener on the table makes sense if the table allows users to further filter the result set using column filters.To override the default QueryListener, copy the existing string referencing the binding layer to the clipboard and then select Edit from the field context menu (press the arrow icon to open it) to selecte or create a new managed bean and method to handle the query event.  The code below is from a managed bean with custom query listener handlers defined for the af:query component and the af:table component. The default listener entry copied to the clipboard was "#{bindings.ImplicitViewCriteriaQuery.processQuery}"  public void onQueryList(QueryEvent queryEvent) {   // The generated QueryListener replaced by this method   //#{bindings.ImplicitViewCriteriaQuery.processQuery}        QueryDescriptor qdes = queryEvent.getDescriptor();          //print or log selected View Criteria   System.out.println("NAME "+qdes.getName());           //call default Query Event        invokeQueryEventMethodExpression("      #{bindings.ImplicitViewCriteriaQuery.processQuery}",queryEvent);  } public void onQueryTable(QueryEvent queryEvent) {   // The generated QueryListener replaced by this method   //#{bindings.ImplicitViewCriteriaQuery.processQuery}   QueryDescriptor qdes = queryEvent.getDescriptor();   //print or log selected View Criteria   System.out.println("NAME "+qdes.getName());                   invokeQueryEventMethodExpression(     "#{bindings.ImplicitViewCriteriaQuery.processQuery}",queryEvent); } private void invokeQueryEventMethodExpression(                        String expression, QueryEvent queryEvent){   FacesContext fctx = FacesContext.getCurrentInstance();   ELContext elctx = fctx.getELContext();   ExpressionFactory efactory   fctx.getApplication().getExpressionFactory();     MethodExpression me =     efactory.createMethodExpression(elctx,expression,                                     Object.class,                                     new Class[]{QueryEvent.class});     me.invoke(elctx, new Object[]{queryEvent}); } Of course, this code also can be used as a starting point for other query manipulations and also works with saved custom criterias. To read more about the af:query component, see: http://download.oracle.com/docs/cd/E15523_01/apirefs.1111/e12419/tagdoc/af_query.html

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• SQL SERVER – SSIS Look Up Component – Cache Mode – Notes from the Field #028

  - by Pinal Dave

  [Notes from Pinal]: Lots of people think that SSIS is all about arranging various operations together in one logical flow. Well, the understanding is absolutely correct, but the implementation of the same is not as easy as it seems. Similarly most of the people think lookup component is just component which does look up for additional information and does not pay much attention to it. Due to the same reason they do not pay attention to the same and eventually get very bad performance. Linchpin People are database coaches and wellness experts for a data driven world. In this 28th episode of the Notes from the Fields series database expert Tim Mitchell (partner at Linchpin People) shares very interesting conversation related to how to write a good lookup component with Cache Mode. In SQL Server Integration Services, the lookup component is one of the most frequently used tools for data validation and completion.  The lookup component is provided as a means to virtually join one set of data to another to validate and/or retrieve missing values.  Properly configured, it is reliable and reasonably fast. Among the many settings available on the lookup component, one of the most critical is the cache mode.  This selection will determine whether and how the distinct lookup values are cached during package execution.  It is critical to know how cache modes affect the result of the lookup and the performance of the package, as choosing the wrong setting can lead to poorly performing packages, and in some cases, incorrect results. Full Cache The full cache mode setting is the default cache mode selection in the SSIS lookup transformation.  Like the name implies, full cache mode will cause the lookup transformation to retrieve and store in SSIS cache the entire set of data from the specified lookup location.  As a result, the data flow in which the lookup transformation resides will not start processing any data buffers until all of the rows from the lookup query have been cached in SSIS. The most commonly used cache mode is the full cache setting, and for good reason.  The full cache setting has the most practical applications, and should be considered the go-to cache setting when dealing with an untested set of data. With a moderately sized set of reference data, a lookup transformation using full cache mode usually performs well.  Full cache mode does not require multiple round trips to the database, since the entire reference result set is cached prior to data flow execution. There are a few potential gotchas to be aware of when using full cache mode.  First, you can see some performance issues – memory pressure in particular – when using full cache mode against large sets of reference data.  If the table you use for the lookup is very large (either deep or wide, or perhaps both), there’s going to be a performance cost associated with retrieving and caching all of that data.  Also, keep in mind that when doing a lookup on character data, full cache mode will always do a case-sensitive (and in some cases, space-sensitive) string comparison even if your database is set to a case-insensitive collation.  This is because the in-memory lookup uses a .NET string comparison (which is case- and space-sensitive) as opposed to a database string comparison (which may be case sensitive, depending on collation).  There’s a relatively easy workaround in which you can use the UPPER() or LOWER() function in the pipeline data and the reference data to ensure that case differences do not impact the success of your lookup operation.  Again, neither of these present a reason to avoid full cache mode, but should be used to determine whether full cache mode should be used in a given situation. Full cache mode is ideally useful when one or all of the following conditions exist: The size of the reference data set is small to moderately sized The size of the pipeline data set (the data you are comparing to the lookup table) is large, is unknown at design time, or is unpredictable Each distinct key value(s) in the pipeline data set is expected to be found multiple times in that set of data Partial Cache When using the partial cache setting, lookup values will still be cached, but only as each distinct value is encountered in the data flow.  Initially, each distinct value will be retrieved individually from the specified source, and then cached.  To be clear, this is a row-by-row lookup for each distinct key value(s). This is a less frequently used cache setting because it addresses a narrower set of scenarios.  Because each distinct key value(s) combination requires a relational round trip to the lookup source, performance can be an issue, especially with a large pipeline data set to be compared to the lookup data set.  If you have, for example, a million records from your pipeline data source, you have the potential for doing a million lookup queries against your lookup data source (depending on the number of distinct values in the key column(s)).  Therefore, one has to be keenly aware of the expected row count and value distribution of the pipeline data to safely use partial cache mode. Using partial cache mode is ideally suited for the conditions below: The size of the data in the pipeline (more specifically, the number of distinct key column) is relatively small The size of the lookup data is too large to effectively store in cache The lookup source is well indexed to allow for fast retrieval of row-by-row values No Cache As you might guess, selecting no cache mode will not add any values to the lookup cache in SSIS.  As a result, every single row in the pipeline data set will require a query against the lookup source.  Since no data is cached, it is possible to save a small amount of overhead in SSIS memory in cases where key values are not reused.  In the real world, I don’t see a lot of use of the no cache setting, but I can imagine some edge cases where it might be useful. As such, it’s critical to know your data before choosing this option.  Obviously, performance will be an issue with anything other than small sets of data, as the no cache setting requires row-by-row processing of all of the data in the pipeline. I would recommend considering the no cache mode only when all of the below conditions are true: The reference data set is too large to reasonably be loaded into SSIS memory The pipeline data set is small and is not expected to grow There are expected to be very few or no duplicates of the key values(s) in the pipeline data set (i.e., there would be no benefit from caching these values) Conclusion The cache mode, an often-overlooked setting on the SSIS lookup component, represents an important design decision in your SSIS data flow.  Choosing the right lookup cache mode directly impacts the fidelity of your results and the performance of package execution.  Know how this selection impacts your ETL loads, and you’ll end up with more reliable, faster packages. If you want me to take a look at your server and its settings, or if your server is facing any issue we can Fix Your SQL Server. Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: Notes from the Field, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL Tagged: SSIS

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• Entity Framework - An object with the same key already exists in the ObjectStateManager

  - by Justin

  Hey all, I'm trying to update a detached entity in .NET 4 EF: [AcceptVerbs(HttpVerbs.Post)] public ActionResult Save(Developer developer) { developer.UpdateDate = DateTime.Now; if (developer.DeveloperID == 0) {//inserting new developer. DataContext.DeveloperData.Insert(developer); } else {//attaching existing developer. DataContext.DeveloperData.Attach(developer); } //save changes. DataContext.SaveChanges(); //redirect to developer list. return RedirectToAction("Index"); } public static void Attach(Developer developer) { var d = new Developer { DeveloperID = developer.DeveloperID }; db.Developers.Attach(d); db.Developers.ApplyCurrentValues(developer); } However, this gives the following error: An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key. Anyone know what I'm missing? Thanks, Justin

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• How to manage GetDate() with Entity Framework

  - by wcpro

  I have a column like this in 1 of my database tables DateCreated, datetime, default(GetDate()), not null I am trying to use the Entity Framework to do an insert on this table like this... PlaygroundEntities context = new PlaygroundEntities(); Person p = new Person { Status = PersonStatus.Alive, BirthDate = new DateTime(1982,3,18), Name = "Joe Smith" }; context.AddToPeople(p); context.SaveChanges(); When i run this code i get the following error The conversion of a datetime2 data type to a datetime data type resulted in an out-of-range value.\r\nThe statement has been terminated. So i tried setting the StoreGeneratedPattern to computed... same thing, then identity... same thing. Any ideas?

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• Creating blob properties with Entity Framework 4?

  - by David Veeneman

  I am creating an EF4 model-first application with a WPF UI. One of the controls on my UI is a RichTextDocument, which outputs a WPF FlowDocument. I can either serialize the FlowDocument to a byte array, or extract its XAML markup as a string. I would prefer to use binary serialization, if I can. Here are my questions: If I serialize to a byte array, how do I specify an entity property as a byte array in the EDM Designer? If I extract a XAML markup string, can I specify that the EDM Designer create the corresponding database column as a nvarchar(max) column? As to the second question, I assume I could always manually edit the MyModel.edmx.sql file to change the data type from nvarchar(4000) to nvarchar(max) before executing it, but I would like to know if it can be done in the Designer. Thanks for your help.

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• How do I delete multiple rows in Entity Framework (without foreach)

  - by Jon Galloway

  I'm deleting several items from a table using Entity Framework. There isn't a foreign key / parent object so I can't handle this with OnDeleteCascade. Right now I'm doing this: var widgets = context.Widgets .Where(w => w.WidgetId == widgetId); foreach (Widget widget in widgets) { context.Widgets.DeleteObject(widget); } context.SaveChanges(); It works but the foreach bugs me. I'm using EF4 but I don't want to execute SQL. I just want to make sure I'm not missing anything - this is as good as it gets, right? I can abstract it with an extension method or helper, but somewhere we're still going to be doing a foreach, right?

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• Repository Pattern and Entity Framework.

  - by vitorcast

  Hi people, I want to make an implementation with repository pattern with ASP.NET MVC 2 and Entity Framework but I have had some issues in the process. First of all, I have 2 entities that has a relationship between them, like Order and Product. When I generate my dbml file it gaves me a class Order with a property that map a "ProductSet" and one class Product with a property that map wich Order that Product relates itself. So I create my Repository pattern like IReporitory with the basic CRUD operations and inside my controllers I implement the ProductRepository or OrderRepository. The problem occurs when I try to create Product and have to assign my Order on it, like ProductOne.Order = _orderRepository.Find(orderId); That operation gave me some strange behavior and I can't find out what is wrong with it. Thanks for the help.

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• Asp.net ADO.NET Entity Framework or ADO.NET

  - by sharru

  I'm starting a new project based on ASP.NET and Windows server. The application is planned to be pretty big and serve large amount of clients pulling and updating high freq. changing data. I have previously created projects with Linq-To-Sql or with Ado.Net. My plan for this project is to use VS2010 and the new EF4 framework. It would be great to hear other programmers options about development with Entity Framework Pros and cons from previous experience? Do you think EF4 is ready for production? Should i take the risk or just stick with plain old good ADO.NET?

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• Entity Framework inheritance: TPT, TPH or none?

  - by silverfighter

  Hi, I am currently reading about the possibility about using inheritance with Entity Framework. Sometimes I use a approch to type data records and I am not sure if I would use TPT or TPH or none... For example... I have a ecommerce shop which adds shipping, billing, and delivery address I have a address table: RecordID AddressTypeID Street ZipCode City Country and a table AddressType RecordID AddressTypeDescription The table design differs to the gerneral design when people show off TPT or TPH... Does it make sense to think about inheritance an when having a approach like this.. I hope it makes sense... Thanks for any help...

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• Entity Framework One-To-One Mapping Issues

  - by Baddie

  Using VS 2010 beta 2, ASP.NET MVC. I tried to create an Entity framework file and got the data from my database. There were some issues with the relationships, so I started to tweak things around, but I kept getting the following error for simple one-to-one relationships Error 1 Error 113: Multiplicity is not valid in Role 'UserProfile' in relationship 'FK_UserProfiles_Users'. Because the Dependent Role properties are not the key properties, the upper bound of the multiplicity of the Dependent Role must be *. myEntities.edmx 2024 My Users table is consists of some other many-to-many relationships to other tables, but when I try to make a one-to-one relationship with other tables, that error pops up. Users Table UserID Username Email etc.. UserProfiles Table UserProfileID UserID (FK for Users Table) Location Birthday

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• Using LIKE operator in LINQ to Entity

  - by Draconic

  Hi, everybody! Currently in our project we are using Entity Framework and LINQ. We want to create a search feature where the Client fills different filters but he isn't forced to. To do this "dynamic" query in LINQ, we thought about using the Like operator, searching either for the field, or "%" to get everything if the user didn't fill that field. The joke's on us when we discovered it didn't support Like. After some searching, we read several answers where it's sugested to use StartsWith, but it's useless for us. Is the only solution using something like: ObjectQuery<Contact> contacts = db.Contacts; if (pattern != "") { contacts = contacts.Where(“it.Name LIKE @pattern”); contacts.Parameters.Add(new ObjectParameter(“pattern”, pattern); } However, we'd like to stick with linq only. Happy coding!

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• ADO.NET Entity Framework or ADO.NET

  - by sharru

  I'm starting a new project based on ASP.NET and Windows server. The application is planned to be pretty big and serve large amount of clients pulling and updating high freq. changing data. I have previously created projects with Linq-To-Sql or with Ado.Net. My plan for this project is to use VS2010 and the new EF4 framework. It would be great to hear other programmers options about development with Entity Framework Pros and cons from previous experience? Do you think EF4 is ready for production? Should i take the risk or just stick with plain old good ADO.NET?

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• How to query Entities in Entity Framework 4

  - by Picflight

  In VS2008, I think it is EF1.0, this works just fine. string queryString = @"SELECT VALUE USERS FROM ProjectDBEntities.Users AS User INNER JOIN ProjectDBEntities.Favorites AS F ON F.FavUserId = User.UserId WHERE F.UserId = " + 3 + " ORDER BY F.CreateDate DESC "; System.Data.Objects.ObjectQuery<User> usersQuery = new System.Data.Objects.ObjectQuery<User>(queryString, context).Include("Detail"); //int count = usersQuery.Count(); foreach (User result in usersQuery) Console.WriteLine("User Name: {0}", result.UserName); Same code in VS2010 EF4 it crashes on the foreach loop with the following error: The result type of the query is neither an EntityType nor a CollectionType with an entity element type. An Include path can only be specified for a query with one of these result types.

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• Best Practices - Data Annotations vs OnChanging in Entity Framework 4

  - by jptacek

  I was wondering what the general recommendation is for Entity Framework in terms of data validation. I am relatively new to EF, but it appears there are two main approaches to data validation. The first is to create a partial class for the model, and then perform data validations and update a rule violation collection of some sort. This is outlined at http://msdn.microsoft.com/en-us/library/cc716747.aspx The other is to use data annotations and then have the annotations perform data validation. Scott Guthrie explains this on his blog at http://weblogs.asp.net/scottgu/archive/2010/01/15/asp-net-mvc-2-model-validation.aspx. I was wondering what the benefits are of one over the other. It seems the data annotations would be the preferred mechanism, especially as you move to RIA Services, but I want to ensure I am not missing something. Of course, nothing precludes using both of them together. Thanks John

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• False Duplicate Key Error in Entity Framework Application

  - by ProfK

  I have an ASP.NET application using an entity framework model. In an import routine, with the code below, I get a "Cannot insert duplicate key" exception for AccountNum on the SaveChanges call, but when execution stops for the exception, I can query the database for the apparently duplicated field, and no prior record exists. using (var ents = new PvmmsEntities()) { foreach (DataRow row in importedResources.Rows) { var empCode = row["EmployeeCode"].ToString(); try { var resource = ents.ActivationResources.FirstOrDefault(rs => rs.EmployeeCode == empCode); if (resource == null) { resource = new ActivationResources(); resource.EmployeeCode = empCode; ents.AddToActivationResources(resource); } resource.AccountNum = row["AccountNum"].ToString(); ents.SaveChanges(true); } catch(Exception ex) { } } }

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• ROO: how to create composit primary key in Entity

  - by Paul

  Hi, What can I do if I need to create entity for a table in production DB (Oracle 10g) with composite primary key. For example: [CODE] CREATE TABLE TACCOUNT ( BRANCHID NUMBER(3) NOT NULL, ACC VARCHAR2(18 BYTE) NOT NULL, DATE_OPEN DATE NOT NULL, DATE_CLOSE DATE, NOTE VARCHAR2(38 BYTE) ); CREATE UNIQUE INDEX PK_TACCOUNT ON TACCOUNT (BRANCHID, ACC); I don't want to change the structure of this table. Is it possible to create an "id" field using roo commands? I use Spring Roo 1.0.2.RELEASE [rev 638] Paul

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• Binding custom property in Entity Framework

  - by deverop

  I have an employee entity in my EF model. I then added a class to the project to add a custom property public partial class Employee { public string Name { get { return string.Format("{0} {1}", this.FirstName, this.LastName); } } } On a aspx form (inside a FormView), I want to bind a DropDownList to the employee collection: <asp:Label runat="server" AssociatedControlID="ddlManagerId" Text="ManagerId" /> <asp:DropDownList ID="ddlManagerId" runat="server" DataSourceID="edsManagerId" DataValueField="Id" DataTextField="Name" AppendDataBoundItems="true" SelectedValue='<%# Bind("ManagerId") %>'> <asp:ListItem Text="-- Select --" Value="0" /> </asp:DropDownList> <asp:EntityDataSource ID="edsManagerId" runat="server" ConnectionString="name=Entities" DefaultContainerName="Entities" EntitySetName="Employees" EntityTypeFilter="Employee" EnableFlattening="true"> </asp:EntityDataSource> Unfortunately, when I fire up the page, I get an error: DataBinding: 'System.Web.UI.WebControls.EntityDataSourceWrapper' does not contain a property with the name 'Name'. Any ideas what I'm doing wrong?

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• Using DataAnnotations with Entity Framework

  - by dcompiled

  I have used the Entity Framework with VS2010 to create a simple person class with properties, firstName, lastName, and email. If I want to attach DataAnnotations like as is done in this blog post I have a small problem because my person class is dynamically generated. I could edit the dynamically generated code directly but any time I have to update my model all my validation code would get wiped out. First instinct was to create a partial class and try to attach annotations but it complains that I'm trying to redefine the property. I'm not sure if you can make property declarations in C# like function declarations in C++. If you could that might be the answer. Here's a snippet of what I tried: namespace PersonWeb.Models { public partial class Person { [RegularExpression(@"(\w|\.)+@(\w|\.)+", ErrorMessage = "Email is invalid")] public string Email { get; set; } /* ERROR: The type 'Person' already contains a definition for 'Email' */ } }

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• Entity Framework Custom T4 Template

  - by s7orm

  Hello, I am using the Entity Framework 4.0 and I am trying to extend my POCO classes generated by the standart T4 template with some custom properties. The classes which are generated by default from EF (without T4) contain 2 properties for every navigation property - NavigationPropertyId and navigationPropertyReference. What I am trying to do is basically extend the generated POCO class with an "Id" property of the foreign key object. I know that I can do that by editing the POCO t4 template. However I have no idea how I can populate/persist the property - I guess I have to somehow extend/modify the method than converts the object to a sql query and vice versa, but I have no idea where to start. Can anyone help? Edit: I just found out, that the EF team has planned to implement something like this - http://blogs.msdn.com/efdesign/archive/2010/03/10/poco-template-code-generation-options.aspx (see Basic POCO with/without Fixup), however this can take ages, so I rather implement it myself.

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• Correct way to perform an update using ADO.Net Entity Model in .net 4

  - by sf

  Hi, I just wanted to clarify if this is the appropriate way to perform an update using a designer generated ADO.NET Entity Model. I was wondering if there was a way to perform an update without creating the sqlMenu object. public class MenusRepository { public void UpdateMenu(Menu menu) { // _context is instantiated in constructor Menu sqlMenu = (from m in _context.Menus where m.MenuId == menu.MenuId select m).FirstOrDefault(); if (sqlMenu == null) throw new ArgumentException("Can't update a Menu which does not exist"); // associate values here sqlMenu.Name = menu.Name; _context.SaveChanges(); } }

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• In separate data access & business logic layer, can I use Entity framework classes in business layer

  - by Greg

  In separate data access & business logic layer, can I use Entity framework classes in business layer? EDIT: I don't think I will need to swap out the data access layer from my business logic in the future (i.e. will be SQL Server), however I will for the UI layer. Therefore the question is more meant to be are there any major issues with using EF classes for me in the business layer? Seems like there would be less plumbing code.

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