VS 2010 : Entity Framework - Specify Read Only Property?
Apr 18, 2012
I'm struggling a bit with Entity Framework 4.x. Let's say I have a model called Product. It was generated from a database table. There is a field in this entity called CreatedDate. The MySQL database has a default value for the current timestamp. I don't want Entity Framework to set this field when inserting or update the table. Problem is, I can't seem to figure out how to tell EF to exclude this field from being sent back to the database, but still retain it as a field to be viewable in the application.
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Apr 6, 2011
I have two properties ("FIRST_NAME" and "LAST_NAME") I need to access as a single property (e.g. "FULL_NAME"). Is there a way for me to add a property to my entity model that contains the combine value of FIRST_NAME and LAST_NAME?
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Mar 21, 2012
I have the following query:
Dim queryStudent = (From p In dbContext.Residents _
Where p.people_code_id = people_id _
Where p.year = year _
[code].....
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Oct 18, 2010
I have a the following setup
m_handsets = From p In RL.App.TComEntities.tblTelephoneNumbers _
Where p.companyId = m_CompanyID _
Select p
m_handsets = DirectCast(m_handsets, ObjectQuery(Of RL.TelephoneNumbers)).Include("tblCalls")
where m_handsets is defined as Private m_handsets As IQueryable(Of RL.tblTelephoneNumbers)
which works as expected however what I want to do know is query the Navigation property (tblCalls) so I can do something like the following From p In m_handsets.tblCalls Where m_handsets.tblCalls.price > 100
I think the complexity comes here because in this instance I could have 5 tblTelephoneNumbers in m_handsets and then x amount of calls for that particular telephone number. I am interested in the tblCalls for each but I would like to filter them all for each tblTelehoneNumber.
Entity Diagram which (hopefully) should illustrate further So I currently know all the handsets that are associated with the company I am interested in. I can also see the calls loaded as a navigation property in debug mode, but I want to say is take this filter (in this example price>100 and apply it to all handsets->calls
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May 13, 2010
c# - Are Microsoft Entity Framework and ADO.NET Entity Framework (.edmx) the same?
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Aug 19, 2011
I just read this post url...Post #2 by jmc states indicates the use of Entity Framework instead of typed datasets.when jmc says something I usually pay attention. I have a large app that I've been converting from VB6 to .Net and I've used mainly typed datasets.It's a single user app that uses an Access database. I'm have no problems retrieving the data from a table or multiple tables and I'm very happy with its preformance.Is it worth scapping what I've done and learn how to use Entity Framework? I should add that I'm near the end of my programming career not the beginning.
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Jul 22, 2009
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:
[Code]....
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Dec 14, 2011
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.
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<Post>()
.Map(m =>
[code]....
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Jan 16, 2011
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.
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Feb 18, 2010
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?
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Jul 22, 2011
Is there any predefined property by which I can set the DisplayFormat/DisplayStyle of a textbox? Suppose I want a textbox to hold the actual value 888888888888.88 and show it formatted as 888,888,888,888.88. In short it should hold 'Double' data type value and show it with thousand separators and decimal places upto two digits. If text is cleared from the textbox, it should have 0 as value and 0.00 as displayed value. Also the number of digits in the textbox may vary accordingly. So how can it be done?
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Jun 6, 2011
Is there any predefined property by which I can set the DisplayFormat/DisplayStyle of a textbox? Suppose I want a textbox to hold the actual value 888888888888.88 and show it formatted as 888,888,888,888.88. In short it should hold 'Double' data type value and show it with thousand separators and decimal places upto two digits. If text is cleared from the textbox, it should have 0 as value and 0.00 as displayed value. Also the number of digits in the textbox may vary accordingly. So how can it be done?
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Apr 17, 2009
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:
[Code]....
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Apr 16, 2011
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.
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Apr 21, 2012
Here are the entities that i have...
Public Class Account
Public Property AccountId As integer
Public Property AccountDescription As String
Public Property Transactions As List(Of Transaction)
End Class
[Code]...
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?
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Sep 28, 2011
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.)
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Feb 28, 2012
I'm trying to learn EF in visual basic. I'm struggling with finding any easy to understand simple tutorial of how to do inner joins.
This is the SQL that i'm trying to replicate in EF:
SELECT Quote.LockedDateTime, IncommingQuoteStatus.StatusDesc, Users.FirstName
+ ' ' + Users.LastName AS UserName
FROM Quote
[Code].....
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Feb 8, 2011
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.
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Nov 3, 2010
I'm currently testing the entity framework 4 for a simple app I wish to build.
how do you save and cancel changes on a record basis? Using the save changes method on the context persists all the changes to the database.
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May 10, 2012
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.
[Code]...
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Jul 7, 2011
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.
[Code]...
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May 14, 2012
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
[code].....
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Apr 6, 2011
I have the following code:
Private Sub btnReserve_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnReserve.Click
Using dbContext As pbu_housingEntities = New pbu_housingEntities
[Code].....
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?
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Dec 20, 2011
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
[Code]...
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Jan 15, 2009
I am just starting out with ADO.net Entity Framework I have mapped two tables together and receive the following error:
Error 1 Error 11010: Association End 'OperatorAccess' is not mapped. E:Visual StudioprojectsBrandi IIBrandi IIHospitals.edmx 390 11 Brandi II
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Dec 28, 2009
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.
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Nov 5, 2010
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?
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Mar 12, 2011
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] .....
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Mar 4, 2009
The question header is clear, i want to know why its different and why, when to select it for my project?
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Aug 24, 2011
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...
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