This is my function:
Public Function GetAllEmployee() As List(Of Employees)
Return DB.Employees.Select(Function(q) New With {q.EmployeeID, q.LastName,q.FirstName}).ToList()
End Function
I'm getting an error:
Value of type System.Collections.Generic.List(Of <anonymous type>) cannot be converted to System.Collections.Generic.List(Of NorthwindModel.Employees).
I've seen many examples in LINQ but i'm not able to reproduce the same result in vb.net.
I have following code: Dim context As New MyModel.Entities()
Dim rnd As New System.Random()Dim gardens As List(Of Tuin) = (From t In context.Gardens Where _
t.Approved = True And _
Not t.Famous = True _
Order By rnd.Next() _
Select t).ToList()
[Code]...
I'm taking a peek at both the Entity Framework and LINQ to SQL, and while I like the systems (and of course the LINQ integration) I'm a little skeptical on the data-binding aspect. I've taken query results and inspected them, and they don't appear to implement the standard .NET list-binding interfaces (IBindingList, and more importantly ITypedList), leading me to believe that binding them to a grid (or anything else) is going to use reflection to get/set my entity properties. This seems like a comparatively expensive operation, especially when all of the code is generated anyway and could implement the interfaces. Is reflection used to get/set the value of the properties?
Edit: I'm actually concentrating on whether or not ITypedList is implemented somewhere along the way, as that's what has the capability to provide an explicit mechanism for defining and interacting with properties without resorting to reflection. While I didn't have a LINQ to SQL project up,I did inspect a simple Entity Framework entity query result, and it did not appear to implement ITypedList.
Edit 2: After accepting Marc's answer, I thought it might be helpful for others if I posted some simple code I used to seamlessly implement his solution. I put the following in the static constructor for my class:
public static ContextName()
{
foreach(Type type in System.Reflection.Assembly.GetExecutingAssembly()[code]....
While this is for LINQ to SQL, I'm sure an equivalent version could be written for the Entity Framework. This will scan the assembly for any types with the Table attribute and add a custom provider for each of them.
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 I know now that forms programs are no longer updated by Microsoft and that WPF is the way to go.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 using Entity Framework in Visual Studio 2010 Beta 2 (.NET framework 4.0 Beta 2). I have created an entity framework .edmx model from my database and I have a handful of many-to-many relationships.
A trivial example of my database schema is
Roles (ID, Name, Active)
Members (ID, DateOfBirth, DateCreated)
RoleMembership(RoleID, MemberID)
[Code]....
For brevity I turned the list of all the columns from the Members table into *
As you can see it's just ignoring the "Role" query.
I am wanting to create a Where statement within my Linq statement, but have hit a bit of a stumbling block.I would like to split a string value, and then search using each array item in the Where clause.In my normal Sql statement I would simply loop through the string array, and build up there Where clause then either pass this to a stored procedure, or just execute the sql string. But am not sure how to do this with Linq to Entity? ( From o In db.TableName Where o.Field LIKE Stringvalue Select o ).ToList()
View 5 RepliesI have many similar calls to database and they work fine
Using ta As New QT_SSTEntities
Return ta.Product.
Select(Function(c) New RadComboBoxData() With {.Text = c.FieldName1, .Value = c.FieldName1}).
[Code].....
I need to grab just one row, and output its name and details properties to a sidebox on my page.So far I have come up with this, which is not working and giving cast errors between the entity and the list of.
Public Shared Function GetOneRow() As String
Dim db As New Model.Entities
Dim rowCount As Integer = (From t In db.Table Select t).Count
[code]....
how I can select a row and column dynamically in EF4? (VB).A bit like a map, I want to navigate through the data using x and y axis to pull out one fields value,SQL would look like this
SELECT " & MyColumbVariable & " FROM MyTable WHERE MyRow = " & MyVariable & "
i have issue returning a list in a web method. here is the code
<WebMethod()> _
Public Function getTags(para_parents As String) As List(Of getTypeDetailsByParentName_Result)()
Dim context As New PPEntities
[code]....
the error is
Value of type 'System.Collections.Generic.List(Of SaftyonRoad.getTypeDetailsByParentName_Result)' cannot be converted to '1-dimensional array of System.Collections.Generic.List(Of SaftyonRoad.getTypeDetailsByParentName_Result)'
I have Customers table in a database. I'd like to create List of CustomerNames using entity framework 4.1. How can I do that in Visual Basic?
Dim customerNames = (From c In _context.Customers
Select New With {c.CustomerName}).ToList()
brings a list of anonymous objects.
c# - Are Microsoft Entity Framework and ADO.NET Entity Framework (.edmx) the same?
View 7 RepliesI 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.)
View 3 RepliesI'm using EF version 4.1, and would like to have the data from the database in realtime, i.e. if you open the application it detects if there is new data in the database, and update the above it! is It possible to do this? I am using EF 4.1 code first time
View 1 RepliesI am having trouble getting the new Entity Framework's objects and classes to store data in my database. I have tried basically everything I can think of, asked for various forums with no success, and I am starting to wonder if the new EF is merely for reading data and not saving it. Now, I decided to make atest Console application to make a single record in the database. The code is quite simple:
Sub
Main()
Dim ent As New MyModelEntities()
[code].....
I have a view on some data in my database it returns the data as I would expect, for example
Call Date To From Phone Number
20/1/2010 00:00 23:59 08923233223
20/1/2010 00:00 23:59 08923233245
However when I have added this to my Entity Model and query it I get duplicate(and unexpected) data appearing
Call Date To From Phone Number
20/1/2010 00:00 23:59 08923233223
20/1/2010 00:00 23:59 08923233223
I am simply binding a Entity Data Source to this Entity but I am left scratching my head as to why the data is being returned differently
EDIT: Interestingly this can't be the result of some strange under the hood join as the row counts match as expected. I have also put together a query myself to test with the same odd results.From o In App.Entities.v_PersonalRules Where o.companyid = CompanyID Select o. I am using Visual Studio 2010, .NET 4
EDIT: The front end code is fairly simple
<asp:EntityDataSource ID="EDS_Personal" runat="server" ConnectionString="name=Entities_NEW"
DefaultContainerName="Entities_NEW" EnableDelete="True" EnableInsert="False"
EnableUpdate="True" EntitySetName="v_PersonalRules" EntityTypeFilter="v_PersonalRules" >[code]....
I have a WCF Windows service that provides data to 250+ PDAs via compressed datasets and was looking to redevelop both the service and the mobile application to use Entity Framework 4.x models. In order to keep performance acceptable when sending/receiving data on the PDA I need to keep the data size as small as possible and was wondering if its possible to compress a IEnumerable from the WCF windows service? From previous experience with the datasets I got a 80%+/- compression rate and even decompressing the data on the PDA achieved an overal 50% performance importment so retaining similar levels of performance is critical. Could I use a binary serializer and then compress the stream?
View 1 RepliesI just read this article about the Entity Framework 4 (actually version 2).Entity Framework seems to offer a huge improvement over its first release. Thus, I have never ever used EF in any project, since I think EF is not mature enough in comparison to NHibernate.NHibernate and its current contributions of FluentNHibernate and Linq for NHibernate by Ayende RahienMy feeling is that Microsoft is solely trying to gain terrain it has lost in favor of NHibernate when the 2nd version of NHibernate came out.Nevertheless, my concerns are the followings (not in particular order):Will EF4 tend to be less XML-verbose?Will EF4 be compatible with other underlying datastore than just SQL Server?What are the greatest benefits of going with EF4 instead of FluentNHibernate or NHibernate itself.
NHibernate is a great tool, I guess everyone agrees. Due to its predecessor Hibernate, we may easily find documentions and tutorials and sample applications to get acquainted with it. This is not the case for FluentNHibernate. Particularly as per the project I'm working on right now which demands that I investigate further about NHibernate and its options (FluentNHibernate for instance) in order to document the rules of usage and the best practices of NHibernat and FluentNHibernate technology. Thus, being handcuffed with VB.NET, being a C-Style developer, I can't find some syntax equivalencies in VB.NET for the examples provided, though I made I way so far
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
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]....
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]....
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.
I am trying to build a survey engine from an existing database design which is like this.
[Code]...
The line Order By Key.RecordOrder throws a null reference exception and I can understand why. Can someone advise on how to resolve this by just modifying this one query? I am fairly new to LINQ and the necessity to write this project
[Code]...
I have a list of "ObjDay" which could have replicated items. How can I select them?
ObjDay is:
Public class ObjDay
_date
...
End Class
[Code].....
I have
Dim objectsList as List(Of Object) = GetAllObjects()
' Filter from Objects just Persons '
Dim peopleList as List(Of Person) = ???
What is the most efficient and effective LINQ expression to do it?
EDIT
1 Dim selectedObjects As List(Of Object) = GetAllObjects()
2 Dim selectedPeople As IEnumerable(Of Person)= selectedObjects.OfType(Of Person)
3 Dim people As List(Of Person) = selectedPeople.ToList()
Error on 3:
Value of type
'System.Collections.Generic.List(Of
System.Collections.Generic.IEnumerable(Of Person))' cannot be
converted to
'System.Collections.Generic.List(Of Person)'.
I have a query that can be summarised in SQL as follows;
Select
S.StockCode
From
StockToCheck As S
[Code]....
Where the S var is a list of strings. This gives the error 'S' is not declared and points to the S in the function call / join (GetPOSStock). So it does not seem possible to do this in Linq, can anyone confirm?
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?
View 10 RepliesI 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]....
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.
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?