How to use entities with DataGridView in visual basic

Question

I'm obviously missing something simple, but how do I display data from an entity framwork model in a DataGridView? Nothing I have tried seems to work!

Answer 1

Hi markev;

Just assign the results of the Linq query to the DataSource property of the DataGridView control.

Dim query = From ...
DataGridView1.DataSource = query.ToList()

If it is not working for you please post your code.

 

---

Fernando (MCSD)

If a post answers your question, please click "Mark As Answer" on that post and "Mark as Helpful".

Answer 2

Thanks - that sorted it (I've tried so many things I've seen I don't know how I missed that)

If I want to use the DataGridView to input data how should I do that?

Mark

Answer 3

Hi markev;

What I would do is to assign the query results to a BindingSource control and then assign the BindingSource control to the DataGridView control. This will allow the BindingSource control to keep the underlaying entities up to date. Then when all CRUD operations are done you will need to execute a SaveChanges to the ObjectContext so that the changes are sent to the database.

Dim query = From ...
Dim bs As New BindingSource()
bs.DataSource = query
DataGridView1.DataSource = bs

---

Fernando (MCSD)

If a post answers your question, please click "Mark As Answer" on that post and "Mark as Helpful".

Answer 4

Thanks for the help, however when I set bs.DataSource = query the program throws the exception below

A first chance exception of type 'System.NotSupportedException' occurred in EntityFramework.dll

 My code is currently

 Private Sub Form1_Load(sender As Object, e As System.EventArgs) Handles Me.Load

        db = New EFContext
        Using db
            Dim item As Item = New Item With {.ItemTitle = "Test"}
            db.Items.Add(item)
            Dim itemQuery = (From d In db.Items Select d)
            Dim bs As New BindingSource()
            bs.DataSource = itemQuery
            'DataGridView1.DataSource = itemQuery.ToList'

            DataGridView1.DataSource = bs

        End Using
    End Sub

Answer 5

Assuming your declairing items as new list(of t)
  db = New EFContext
        Using db
            Dim item As Item = New Item With {.ItemTitle = "Test"}
            db.Items.Add(item)
            Dim itemQuery = (From d In db.Items Select d).tolist <---add this to the query
            
           DataGridView1.DataSource = itemquery

        End Using

Answer 6

The code you posted should have worked. Can you tell me on what line of code did it throw the exception on?

---

Fernando (MCSD)

If a post answers your question, please click "Mark As Answer" on that post and "Mark as Helpful".

Answer 7

Hi

Sorry my previous post was not well worded. The exception occoured on the line

bs.DataSource = itemQuery

I don't know if its related, but I also tried following a blog by Julie Lerman http://thedatafarm.com/LearnEntityFramework/tutorials/use-an-entity-framework-entity-as-a-winforms-data-source/ but that failed when I tried to drag the items object from the datasource window to the form with the following error.

An error occurred while performing the drop:

BindingSource unable to create list based on the Type specified in the DataSource property.

Also don't know if it's relevant, but I am using EF 4.1 and visual basic 2010 express. I can't update to EF4.2 as the nugget tool isn't available for VB express.

Many thanks for your help.

Mark

Answer 8

Hi Mark;

I have no clue why it is throwing an exception on that line of code. If you can zip the project up with the test database and upload both to somewhere on the net so that I can download and have a look I will try and find the issue. If you have a Windows Live account you can upload to your SkyDrive at http://skydrive.live.com/.

---

Fernando (MCSD)

If a post answers your question, please click "Mark As Answer" on that post and "Mark as Helpful".

Answer 9

Hi Fernando

I have uploaded the file to skydrive -

https://skydrive.live.com/redir.aspx?cid=c8f782ed6d38cb27&resid=C8F782ED6D38CB27!229&parid=C8F782ED6D38CB27!228&authkey=!AMfbOKy2BRocEQo

I haven't uploaded a database as EF creates the db on the fly.

Mark

Answer 10

Hi Mark;

The error message that is returned from the exception 'System.NotSupportedException' is as follows :

"Data binding directly to a store query (DbSet, DbQuery, DbSqlQuery) is not supported. Instead populate a DbSet with data, for example by calling Load on the DbSet, and then bind to local data. For WPF bind to DbSet.Local. For WinForms bind to DbSet.Local.ToBindingList()."

The issue is that a Linq query when NOT enumerated is NOT holding a result set but the query itself. To resolve the issue you need to enumerate the query by adding the method ToList() at the end of the query as follows:

Dim itemQuery = (From d In db.Items Select d).ToList()

 

---

Fernando (MCSD)

If a post answers your question, please click "Mark As Answer" on that post and "Mark as Helpful".

Answer 11

Hi Fernando

Thanks for your help that's brilliant. Just got to sort the rest of the program logic!

Mark