Create an object in Visual Basic (not VB.NET) without using "New"

Question

I've been told to think outside the box, and think of a way to create an object in VB without using the new keyword. I was told it is possible but i'm having trouble figuring it out. I know primitive data gets stored on the stack and the reference to the objects get stored there too but the actual memory space for the object is in the heap and that new does that for us. When i try it without new i mostly get null reference exception, any ideas on how this is possible?

Dim objTest as TestOne()

'some class named TestOne with empty Constructor

What happens if you evaluate an expression like (1+2).ToString()? — supercat
– supercat, Commented Oct 26, 2019 at 23:50
Maybe you should specify what that older version is and edit your question accordingly. We shouldn't have to guess stuff like that. You need to provide a FULL and CLEAR explanation of the problem. What language it's for is obviously part of that. — jmcilhinney
– jmcilhinney, Commented Oct 27, 2019 at 3:38
I've changed the title to specify this is a VB question, not VB.NET - as per OP's comment. — HTTP 410
– HTTP 410, Commented Oct 27, 2019 at 13:51

HTTP 410 · Accepted Answer · 2019-10-28 15:14:59Z

2

In VB you can use the CreateObject function if you have an existing class defined in a COM library that you've created - or a COM library that already exists.

As an example, create a project reference to the Microsoft Scripting Runtime COM library (scrrun.dll). To do this in the VB IDE select Project, References, then pick the reference 'Microsoft Scripting Runtime'. You can then write the following code:

Dim fso As Object
fso = CreateObject("Scripting.FileSystemObject")

edited Oct 28, 2019 at 15:14

answered Oct 27, 2019 at 14:16

HTTP 410

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2 Comments

a-exelle Over a year ago

do i need to import something because it does not work. also set keyword is no longer supported by VB. .

HTTP 410 Over a year ago

@a-exelle, I've now made my answer VB-specific.

Visual Vincent · Accepted Answer · 2019-10-27 11:31:05Z

1

I haven't done VB for quite a while now, but the Activator exists in both C# and VB. Here's couple lines of C# that you can convert to VB:

var newThing = (TestOne)Activator.CreateInstance(typeof(TestOne));
newThing.ID = 5;

The CreateInstance method returns an object, which I convert to the correct class with

(TestOne)

which is the C# syntax for type conversion. Sorry, I forgot how to do this in VB.

Where class 'TestOne' looks like:

class TestOne {
    public int ID { get; set; }
}

Note that 'Activator' is part of .NET reflection.

edited Oct 27, 2019 at 11:31

Visual Vincent

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answered Oct 27, 2019 at 0:15

ActualRandy

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5 Comments

a-exelle Over a year ago

when i try this it says testone is a class type and cannot be used as an expression

a-exelle Over a year ago

i was able to get it to work, thank you very much i just had to use getType instead of type of. you were helpful so thank you again!

MarkJ Over a year ago

That's VB.Net, not Vb6. I changed your question tags to VB.Net.

HTTP 410 Over a year ago

@MarkJ, the OP's original code indicates the older version of VB (so not VB.NET). And in a comment on October 27, the OP says it's the older version of VB. So now I'm really confused!

MarkJ Over a year ago

I share your confusion to be honest! But VB.Net first came out in 2002 so it certainly could be described as "older" 17 years later... And the OP said that Set is no longer supported in VB in one comment - that's true, it is no longer supported in VB.Net.The original code in the question could be VB6 or VB.net. Activator.CreateInstance in this answer is certainly VB.Net and the OP says it works for them. That's why I went with VB.Net.

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