Structure Inside Another Structure Receives Null Reference Error?

Jan 5, 2012

Module Module1
Public Structure structure1
Public TRANS() As structure2
End Structure
Public Structure structure2
Public X() As Integer
End Structure
End Module


Class Structure - Large Structure That Has Lots Of Properties ?

Jan 5, 2010

I'm new to VB 2008 after having spent a long time with VB6, so I apologize if this is a stupid question. But I'd really like to have this straightened out.

Let's say I have a pretty large structure that has lots of properties.


Now say that I want an internal database with about 10 instances of this structure total, describing, say, 10 different products that a store sells. When these values are loaded from a database, they remain totally static. (However, they can be different each time a program loads)

Now say that I have a class. Each instance of this class is a type of that BaseProduct structure. Meaning, each instance of the class pertains to one of the 10 types of products that the store sells. However, this class has additional properties that pertain specifically to each instance, which are not static.


Now, the problem here is... If I have 200 different transactions, each one contains an instance of BaseProduct. BaseProduct is HUGE, and is largely redundant (only 10 types possible), so I think it's a little silly to include a whole copy of it with EVERY transaction. However, the Transaction class really needs information regarding the base product it pertains to. Is there a way to, instead of declaring a New BaseProduct in the Transaction class, to simply make one of the properties of the Transaction class a pointer to a BaseProduct variable?

In VB6, I would accomplish this by making a BaseProduct(10) array, and then giving each Transaction an ID number referring to an entry in that array. But in VB 2008, using class structure, this is impossible. I can't define the BaseProduct(10) array outside of a class in a namespace, and if I define it in the actual application's form, then the class loses modularity since it relies on the application that's using it.

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I have to send data based on a struct that embeds 2 other struct. So here's my code for the struct used to convert to byte array and the sending part.

Public Structure MESSAGETYPE_OIP_Login
Dim UserName() As PSTRING


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Structure BookData 
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<?xml version="1.0" encoding="utf-8"?>
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Now it is
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Function Example() as integer
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end structure

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Public Structure dx_entry
<MarshalAs(UnmanagedType.ByValTStr, SizeConst:=10)> _
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