I was looking for a way to pass a parameter by reference today. More specifically the setter.
I found a couple interesting blog posts
http://geekswithblogs.net/akraus1/archive/2006/02/10/69047.aspx
notice the comment by Tedesco.
He offers a nice way to do this via an anonymous delegate.
public delegate void InsertString( System.String param );
public partial class Bird
{
public void FileToDb( int x)
{
FillEntityColumn(delegate( System.String value) {tExtra.Text = value; });
}
}
So we actual pass the FillEntityColumn method an anonymous delegate which then sets the property.
Now in vb you can write
Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
testme(TextBox1.Text)
End Sub
Sub testme(ByRef s As String)
s = "hello"
End Sub
End Class
which a commenter on http://musingmarc.blogspot.com/2006/04/tale-of-two-implementations.html eluded to. But in vb you still cannot pass a Property by reference, at least not really. Take a look what vb generates into il.
Private Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs)
Dim VB$t_ref$S0 As TextBox = Me.TextBox1
Dim VB$t_string$S0 As String = VB$t_ref$S0.Text
Me.testme((VB$t_string$S0))
VB$t_ref$S0.Text = VB$t_string$S0
End Sub
As you can see vb is writing some code for you which is nice, but we are still not passing the property by ref.
-
Mike has also talked about the want of passing parameters. ( the same misguided comment that vb supports passing parameters by ref)