VB.NET and the WITH statement

by Svelmoe 20. April 2009 20:23

I love using the WITH statement in VB.NET/ASP.NET because it eases up on the typing and helps “group together” functionality.
However, I found a fun little something when using the WITH statement, which I wanted to share.

It seems that you can assign a new object reference within a WITH statement to the specific object, however you can’t assign values to said new reference. Strange indeed, but I’m sure there’s some underlying reason.
Here some code to illustrate.

Suppose I have a class:

Private Class Test
        Private m_Text As String

        Public Property TextValue() As String
            Get
                Return m_Text
            End Get
            Set(ByVal value As String)
                m_Text = value
            End Set
        End Property
End Class

Then I have some code which uses this class in a WITH statement:

Dim obj As New Test()
obj.TextValue = "Test"
  For i As Integer = 0 To 10
   With obj
     If Not String.IsNullOrEmpty(.TextValue) Then
          System.Diagnostics.Debug.WriteLine("VALUE: " & .TextValue)
    Else
         System.Diagnostics.Debug.WriteLine("VALUE NOTHING")
    End If
    obj = New Test()
    .TextValue = "test" & i
   End With
Next

When run this provides the output:
VALUE: Test
VALUE NOTHING

And "nothing" for every subsequent run.
So it is possible to assign a new reference to the “obj” object reference, but the assignment of the new TextValue is ignored.

Not that usefull, but fun enough in my book :) (yes, I’m a geek

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About Svelmoe

My real name is Allan Svelmøe Hansen.

I live in Denmark, where I work as a developer for hedal:kruse:brohus using SQL Server and the .NET framework since 2004. Svelmoe.dk is a place for my every day thoughts and reactions and the occasional technical blog entry.

I also blog about SQL and MS SQL Server but have moved those posts to www.sqlstuff.dk so in case you are looking for more about that, please visit that website.