vb.net null

If you have a conditional statement and you want to kill all numbers less Y my intuition tells me to set x to null which does not work.

If x < y Then

x = null

Else

x = x

Print("Point passed" & x)

End If

A = x

_______________________________________________________________

If I set x to "null" it returns null because it is a string which is an invalid argument.

This works but what is the correct way to kill or make all values less than Y null?

If x < y Then

x = "null"

Else

x = x

Print("Point passed" & x)

End If

A = x

Replies to This Discussion

Permalink Reply by Damien Alomar on July 13, 2010 at 7:29pm

There are certain data types in .Net that cannot be null (or Nothing which is the VB.Net keyword). Any number type (ints, doubles, singles, longs, etc) cannot be null. Those values all have a default value of 0 (or 0.0). Assigning Nothing to those variables just sets the value back to the default.

Also, VB.Net is a Strongly Typed language, which mean two things, A) you must specify the type of a variable when its declared, and B) the type of the variable cannot change. So you don't really even have the option to assign a string to that variable either.

Permalink Reply by Charles Aweida on July 13, 2010 at 8:46pm

Thanks for the post Damien, with that being said, how would you write a vb conditional statement that deletes all circles less than a specific number, if im not mistaken zero it is technically still a value and would not delete the circles. Maybe you would have to cull the circles....

Permalink Reply by David Rutten on July 14, 2010 at 2:51am

For i As Int32 = CircleList.Count - 1 To 0 Step -1

   If (CircleList(i).Radius < min_radius) Then CircleList.RemoveAt(i)

Next

Note that you have to run through the list backwards, otherwise the items you remove will play havoc with the remainder of the loop.

--
David Rutten
david@mcneel.com
Poprad, Slovakia

Permalink Reply by Charles Aweida on July 15, 2010 at 3:02pm

Thanks for the reply David, I wouldn't have thought to use CircleList.Count is that a variable that you defined or is that a method within the library, speaking of methods where can I find documentation with explanations of the different methods? For example if I wanted to make a line from two points in VB.net where would I find the documentation to do so (similar to the Processing line method) if there is such a thing in VB. I apologize for my lack of knowledge...
Thanks again

Permalink Reply by David Rutten on July 15, 2010 at 3:18pm

Hi Charles,

Count is a readonly property of the List class. Most classes in the .NET framework have properties and methods attached to them. You can use the online MSDN pages to find out all about a particular class and its members.

At the time of writing this is the MSDN help topic for the List(Of T) type. But note that Microsoft often juggle their urls, so the link might expire at any moment.

Usually if you google a specific class name+namespace, the msdn page will be the first hit.

--
David Rutten
david@mcneel.com
Poprad, Slovakia

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