VB - Entity Framework 4.1: Describe Relationship Into The DbContext Definition Using A Fluent Code First Approach?
Dec 5, 2011
I have in my database a table (AccessControl) that describes a sort of users "access control list" for the informations contained in the table Customers and other tables.Example: the entity CUSTOMER is marked by the EntityId #1. If a user belongs to the department #6, he can access the records of customer #16 and #31, but he can't for #14, that can viewed by user in department #3:
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How can I describe this relationship into the DbContext definition using a fluent Code First approach?
Entity Splitting: one class, two or more tables.Here is how it is done in C#, but I need to get it working in vb.net.One more thing: the class name and table columns do not match, so I have to be able to map that out, too.I have to get this to work this way because the place I'm working at right now is a vb.net only shop and the database schema is fubar, but they have so much (millions) of lines of code done directly against the database in both asp classic, vb.net, AND asp.net webforms that changing the schema right now is not realistically possible.
I have a simple Entity Framework. For simplicity's sake I will transform the entity names to Northwind Like.I have a IEnumerable Of Customer and Item Objects
In entity framework we can use 3 approaches model first , code first , database first but each one of them needs manual hand touch(means creating database or create model or write the POCO class codes or entity class codes) before proceeding to the next step ( using EF in context ).What if I want to create database and tables and table relationships programatically and still want to have to features of EntityFramework 4.3.
To be more specific ,from this example http://support.microsoft.com/kb/307283 we can create database , tables and everything using SQL command but we can't have the advantages of entity framework. So if we want to have that what should we do? To give the ability to create dynamic table fields those steps will not be sufficient. In all 3 steps database , table and table columns are fixed. There is no way that a user can create new tables or columns dynamically. http:[url].... in this post , it shows how to create manual db, tables and etc using SQL but it is based on ADO.NET but I want Entity Manager to do that.
I am using Entity Framework 4.1 code first+MVC3 and the inheritence stratagy that I use is TPC
I have the following classes Public Class ObjectBase <Key()> Public Property Id As Integer Public Property Description As String End Class
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Question 1 (and question 2) should be very simple, but I have allready spent hours on Google to find an answer with no result at all. The only thing I have found is that you can get all computers in ObjectBase by writing context.ObjectBase.OfType(Of Computer), and that does not help since you cannot write context.BorrowObjects.ObjectBase.OfType(Of Computer) code samples in VB.NET (if you can), but more importantly: Please ensure that the codesamples you supply work without hours of modification!
I want to update an entity without loading the entity from the database first. I've accomplished this but only by knowing all of the entities properties and then using the "attachto" method. My issues is i don't want my app to need to remember all of the properties. Example:
If I a many-to-many relationship between Users and Roles and I have an instance of a User entity and several Role Ids can I insert a relationship between the two types of entities without having any other Role data and without doing a select on the Roles first? Update:
I might not have been clear enough. I don't have an instance of a Role, only the role id. Is it possible to create the relationship between User and Role without filling a Role object from the database first?
I am trying to jump from ASP Classic to asp.net. I have followed tutorials to get Entity Framework and LINQ to connect to my test database, but I am having difficulties figuring out ExecuteQuery(). I believe the problem is that I need an "entity class" for my database, but I can't figure out how to do it. Here is my simple code:
Dim db as New TestModel.TestEntity Dim results AS IEnumerable(OF ???) = db.ExecuteQuery(Of ???)("Select * from Table1")
From the microsoft example site, they use an entity class called Customers, but I don't understand what that means.
My company is tossing around the idea of using the Entity Framework when it comes out with .NET 4. We are currently a VB.NET shop, but have some interest in switching to C#.Is there any major arguments for or against such a move?Does EF with C# hold any advantages in performance, coding ease, etc over VB.NET?
I am a newbie. I have been able to Add new entities where there is a One-To-Many Relation. I am having a problem (don't Know how to do it) adding a new Entity when the relation is using Many-To-Many. In my EDM I have:
I downloaded the VB 2010 Express software, the total files that we included in the download was 15, but it only loaded up 12 of these files. The following downloads did not get loaded as follows:MS Visual Studio 2010 ADO.NET Entity Framework Tools
MS HelpViewe 1.0 x64
I tried reinstalling the downloads that did not using the VB Express 2010 setup, but they do no appear on the list of downloads, only the SP1 for MS SQL Server 2008 Express Server (x64).Do I require the downloads that did not load.
Public Class Account Public Property AccountId As integer Public Property AccountDescription As String Public Property Transactions As List(Of Transaction) End Class
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i would like to make it suc that when i do "db.Account.find(1)" for example it also loads in the list of all transactions which have the coresponding AccountId. I'm not too sure what type of relationship this is?? anyway, right now i can do
Dim acct As Account = db.Account.Find(1) acct.Transactions = from ts in db.transactions select ts where ts.AccountId = acct.accountid but i know this is not the correct way, there must be a way to map this out so that entity can just load everything in one shot right?
I am used to using datasets for my projects in terms of data access. I now set myself an easy app to work on in order to learn the entity data framework and how to retrieve & manipulate data.Can anyone guide me through on where to start, what are the advantages of this model, In what scenarios should I choose to use entity framework and what are the things (basis) I should now before starting.My datasets are working fine too. Are there any reasons for me not to stick with that way of accessing data? Or is this something to consider depending on the users of the website (for speed purposes etc.)
I have some basic expirience in Visual Basic and programming Windows Forms programs. I know now that forms programs are no longer updated by Microsoft and that WPF is the way to go. No to mention the slicker interface you can create. I've also noticed that passing SQL strings to a database is no longer the standard either. It's either Entity Framwork or Linq.
So I am going for a fresh approach. I need to develop a program that will access a sql database and be accessed by about 10 concurrent users within the office. What's the best approach in general? Linq or Entity Framework? Also, could you recommend a book or two for someone who is new to WPF and Entity Framework? I do have some programming expirience, just none with WPF or the new ways of ADO.net 4.
I'm trying to use the Entity Framework to create a complex query and get stuck in the joins. After browsing some of the documentations, I cannot seem to find the correct solution, so maybe someone here can help.
I have a data structure where a family has several family members, each of which can have more than one entry in the income table (on different registration dates) and can have more than one entry in the healthconditions table.
I need to make a if-else statement in the query meaning I only want to add the OpenAmount to ExpectedAmount if the type = Cash, the problem is that it only gives me the cash row not the other row.
I'm working on a project that was built using ADO.NET (raw sql) and Active Record pattern. I am slowly moving it away from ADO.NET to Entity Framework Code First 4.3.Here is an example of the pattern. The interface is a static Load and an instance Save (and Delete -- not shown).
Public Class Part Public Property Id as Integer Public Shared Function Load(_id As Integer) As Part
Private Sub btnReserve_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnReserve.Click Using dbContext As pbu_housingEntities = New pbu_housingEntities
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executes it always get 0, because the row has not yet been created in the database. I can just move this last bit of code out into its own Context, but is there a better way to do this?
I am trying to make an MVC index view with bulk editing functionality, but can't seem to get it working. I have replaced the Html.DisplayFor with HTML.editorfor items, and put the whole table in a form which submits back to my index function. I have tried various ideas, but currently my function is
So, when you bind a collection of Entity objects to a grid component, the grid displays those fields in the sequential order they are found in the SQL Table they came from. This shows that the ordinal position of the fields are associated with their corresponding entity properties... somehow or other.
So here is the question: How can I obtain the table field ordinal position by reflecting over an Entity Framework Entity's properties? Let me tell you what I know and what I have tried. Apparently, each data field property in an EF Entity is decorated with a System.Runtime.Serialization.DataMemberAttribute. This attribute appears to have an Order property. However, I have discovered that this property does not contain what I am looking for. The value for all Data Properties in an Entity seems to be -1. What ever order is, it isn't ordinal position.
I noticed in the Entity Framework designer that you can map stored procedures for Insert, Update, and Delete operations. Is there any way to do this for Select operations as well, or is there a new direction for database access code where we don't really write stored procedures for our basic select operations any more?The company I work for is pretty adamant about always using stored procedures for every database operation, even though the Entity Framework makes the calls safe by calling sp_executesql.It seems like both LINQ to SQL and Entity Framework have moved away from using stored procedures for selecting the data. Is this an accurate statement?Just to clarify my question:I have a table in my database called Product. I use the wizard in the Entity Framework to generate my models...so I now have an Entity called Product. When I do the following query:
db.Products.SingleOrDefault(p => p.Id == 1);
It generates code similar to:
EXEC sp_executesql N'SELECT * FROM Product'[code].....
If it's not possible to do that using SingleOrDefault I'm fine with that. I'd much rather have the following:
db.Products.GetProduct(1);
Is this something that is normally done or do most people just have it dynamically generate the SQL?
I'm brand new to the Entity Framework and trying to learn all it can offer. I'm currently working my way through the MVC Music Store tutorial which includes the following code:
public ActionResult Browse(string genre) { // Retrieve Genre and its Associated Albums from database var genreModel = storeDB.Genres.Include("Albums") .Single(g => g.Name == genre); return View(genreModel); [Code] .....
The problem is I'm getting the following exception: Invalid column name 'GenreGenreId'. Which I know is true, but I can't for the life of my work out where it's getting 'GenreGenreId' from.
Here is the source for my classes: Album.vb Public Class Album Private _title As String Private _genre As Genre Private _AlbumId As Int32 [Code] .....
I have 2 entities that are related, but the legacy sql schema essentially has 2 key columns for the same table (not a 2-column key: see below). I need to create a relationship back to the 'faux key' column. Is there a way to do this declaratively in Entity Framework 4.1?
Public Class Client Inherits ModelBase <Key(), Required()> Public Property ClientID As Decimal <Required(), StringLength(50)> Public Property ClientCode As String .....
And the error I am getting is: One or more validation errors were detected during model generation: System.Data.Edm.EdmAssociationConstraint: : The types of all properties in the Dependent Role of a referential constraint must be the same as the corresponding property types in the Principal Role. The type of property 'ClientCode' on entity 'ClientLocation' does not match the type of property 'ClientID' on entity 'Client' in the referential constraint 'ClientLocation_Client'.
Because it thinks I'm trying to map ClientLocation.ClientCode > Client.ClientID, when I am really trying to map ClientLocation.ClientCode > Client.ClientCode...
I am trying to figure out Entity Framework but I keep running into issues with the context. I create my .edmx file and it works fine but when I try to declare my context on my pages Visual Studio will not find them. My .edmx file is called YCLModel.edmx and my connectionstring for it is YCLEntites.
I try to declare the context as:
Dim yclcontext as new YCLEntites
I have also tried going into design mode and dragging from the toolbox but when I select my named connection it gives me the following error:
The metadata specified in the connection string could not be loaded. Consider rebuilding the web project to build assemblies that may contain metadata. The following error(s) occurred: Unable to load the specified metadata resource.
