Visual Basic

3-Dec-08 20:34

In C# I have a form which creates an object of my class DirtyMarker for which I pass (among others) a reference to my closeControl.

In the DirtyMarker class I have this code:

pCloseCtrl.Click += new EventHandler((pObj, pArgs) =>
                {
                    if (this.formIsDirty)
                    {
                        MessageBox.Show("There are unsaved changes, please save the changes before closing.");
                    }
                    else
                    {
                        pForm.Close();

                    }
                });

How would I do this in VB?

My concern is not with the anonymous function, but rather with adding the "new" event.

Regards!

Tom Deketelaere3-Dec-08 22:36

3-Dec-08 22:36

Adding an event is done by using the 'Addhandler'

Addhandler pCloseCtrl.click, addressof EventHandler(pObj,pArgs)

private sub EventHandler(pobj as object,pargs as eventargs)
'do your code here
end sub

evilnoodle wrote:
anonymous function,

don't really know how to do this in vb
But when converting the code using:

http://www.developerfusion.com/tools/convert/csharp-to-vb/[^]

I get:

AddHandler pCloseCtrl.Click, AddressOf Function(pObj, pArgs) Do
    If Me.formIsDirty Then
        MessageBox.Show("There are unsaved changes, please save the changes before closing.")
    Else
        pForm.Close()
       
    End If
End Function

Never done it like that tho so don't really know if it works like you want it.

Hope this helps

MatthysDT4-Dec-08 2:10

4-Dec-08 2:10

Thanks but...

Your second solution is a far miss, VS wont accept that syntax.

The first solution is closer but when I do the EventHandler(pObj, pArgs) I get a compile time error stating that: 'AddressOf' operand must be the name of a method (without parentheses)
When I remove the parenthesis, it works but I get a NullReferenceException on that same line at runtime.

Any ideas?

Tom Deketelaere4-Dec-08 2:20

Re: Adding an event (C# code in VB) [modified]

4-Dec-08 2:20

evilnoodle wrote:
Your second solution is a far miss, VS wont accept that syntax.

Could be didn't really test it its just the code you pasted run thru the converter. (did think it kinda looked strange)

evilnoodle wrote:
The first solution is closer but when I do the EventHandler(pObj, pArgs) I get a compile time error stating that: 'AddressOf' operand must be the name of a method (without parentheses)
When I remove the parenthesis, it works but I get a NullReferenceException on that same line at runtime.

Your function (eventhandler) has to take the same parameters as the event it is delcared for (usually it "sender as object, e as eventargs")

so the code becomes

AddHandler frm.Click, AddressOf EventHandler


    Private Sub EventHandler(ByVal pobj As Object, ByVal pargs As EventArgs)
        'do your code here
        MessageBox.Show("test")
    End Sub

This works on my end. Can you post your code so I can see what might be wrong.

MatthysDT4-Dec-08 19:56

4-Dec-08 19:56

Here is what I have so far, I get a NullReferenceException on the AddHandler line.

This is not the same code as the DirtyMarker, but it comes down to the same implementation. This code is supposed to do something when the main form's Datagridview fires userDeletingRow.

Also please ignore the fact that this is a generic type class, I'll focus on that when I get these events to work.

Public Class DataFormLogic(Of T)

    Public Sub New(ByRef DGV As DataGridView)

        AddHandler DGV.UserDeletingRow, AddressOf MyDelete

        'Also tried this, which give a delegate signature error at compile time
        'AddHandler DGV.UserDeletingRow, New EventHandler(AddressOf MyDelete)

    End Sub
    
Private Sub MyDelete(ByVal sender As Object, ByVal e As System.Windows.Forms.DataGridViewRowCancelEventArgs)
        MsgBox("Eureka!!!!!")
    End Sub
End Class

-----------------------------------
UPDATE:

I just got it to work with a button on that same form, it must have something to do with the DataGridView... oh how I loathe that control! Could you try to get it going with a datagridview?

modified on Friday, December 5, 2008 3:32 AM

Tom Deketelaere4-Dec-08 20:54

4-Dec-08 20:54

This works without a problem at my end (see my code below).
My only thought would be that you call this class before the datagridview is created.

The form has a datagridview on it called datagridview1 (original I know)

Public Class Form1
    Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        Dim dt As new DataTable()
        dt.Columns.Add(New DataColumn("Col1"))
        dt.Columns.Add(New DataColumn("Col2"))
        Dim row As DataRow = dt.NewRow
        row.Item("col1") = "col1"
        row.Item("col2") = "col2"
        dt.Rows.Add(row)
        row = dt.NewRow
        row.Item("col1") = "col11"
        row.Item("col2") = "col22"
        dt.Rows.Add(row)
        DataGridView1.DataSource = dt
        Dim temp As New Class1(DataGridView1)
    End Sub
End Class

Public Class Class1
    Public Sub New(ByRef dgv As DataGridView)
        AddHandler dgv.UserDeletingRow, AddressOf mydelete
    End Sub
    Private Sub mydelete(ByVal sender As Object, ByVal e As System.Windows.Forms.DataGridViewRowCancelEventArgs)
        MessageBox.Show("Eureka!!!!")
    End Sub
End Class

This works perfectly for me.
When do you create the instance of the class?

MatthysDT4-Dec-08 21:36

4-Dec-08 21:36

Wow you reply fast, you're either in my time zone, or you never sleep!

That was EXACTLY my problem thank you very much! Funny thing is, I figured it out just before reading this post.

I instanciated the object globally, i.e. before the dataGridView existed, after moving the code to the Load (same as you did) it worked fine!

5!

Tom Deketelaere4-Dec-08 21:40

4-Dec-08 21:40

evilnoodle wrote:
Wow you reply fast, you're either in my time zone, or you never sleep!

A bit off the both Smile | :)

(my average sleep a day is around 4 hours)

evilnoodle wrote:
thank you very much

Your very welcome, glad to be off help where I can

evilnoodle wrote:
I figured it out just before reading this post.

Even better you'll remember it longer that way Smile | :)

Gideon Engelberth4-Dec-08 3:01

Gideon Engelberth

4-Dec-08 3:01

AddHandler pCloseCtrl.Click, AddressOf ClickHandler

Private Sub ClickHandler(pObj As Object, pArgs As EventArgs)
    'your code here
End Sub

The current version of VB does not support multiline delegates, so it is not possible to use the anonymous function syntax.

To remove the event, you use the same syntax except you say RemoveHandler instead.