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

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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.

Code:

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.

Code:

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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Aug 29, 2009

I am trying to communicate with an external device and i am trying to send a byte array to the external device via sockets but i am always getting a response the message size is too small so i am not sure what i have done wrong. Between the data type there should be no alignment present and all numbers are represented in little endian format. The char array is not null terminated as mentioned in the protocol specifications.

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

Public Structure MESSAGETYPE_OIP_Login
Dim Header() As COMMANDHEADER
Dim UserName() As PSTRING

[Code]....

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May 17, 2012

I'm trying to create a structure and inside it put an array of "Genres". This is my structure declaration:

Structure BookData 
Dim strGenres() As String     

[code]....

But I keep getting an error with the .strGenres(5). VB is telling me "End of statement expected"

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Apr 14, 2012

I'm experiencing a problem with the following c-structure:

typedef struct tagTEXTUREPROP
{
DWORD dwSize;

[Code].....

The Marshal.SizeOf obviously calculates a size of 76 and it works with the DLL function, but it leaves me with some bad feelings.

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Apr 25, 2010

I'm having a problem that's driving me crazy; I can't understand how to convert the XML structure into a class structure (that I want to use to hydrate a XML document).

The XML document looks like this:

xml
<?xml version="1.0" encoding="utf-8"?>
<artists xmlns:opensearch="http://a9.com/-/spec/opensearch/1.1/" xmlns="http://www.spotify.com/ns/music/1">

[code]....

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May 19, 2009

I have an enum that I want to give some methods. I thought about changing the enum to a structure so I could add properties, but then the enum is a value inside the structure (not the structure itself), so this would affect comparisons and such. (For example, instead of writing
EnumVariable=EnumConstant,
Now it is
StructureVariable.EnumValue=EnumConstant).
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Jul 10, 2009

In what situtations is it best to use reference arguments to return values?

Sub Example(byref value as integer)
value = 3
End Sub

In what situations is it best to return the value (perhaps in a structure for more complex types)?

Function Example() as integer
return 3
End Function

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Jun 6, 2011

What is the side effects of defining a structure inside a class (name it X), and create a property inside that class of the type X?

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Jan 31, 2010

I have problems with array of structures.my structures are like this

structure order
xxxxxxxxxxx
yyyyyyyyyy
zzzzzzzzzzz
end structure

and then I created many array of structures, like this private arrayorder (100) as order

now i need to sort the entire xxxxxx member of the array of the structure with a function, but I dont want to use loops with arrays indexes to access the information. I want to know if there is another method to reference the array and the member of the structure to get the data.

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Is it okay for a structure variable to hold a small number of reference types?  I thinks it's fine because the pointers themselves are not that big, regardless of what they're pointing to.  But I never did fully figure out the whole heap/stack thing, so I'd like to make sure.

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, I was wondering if it was possible to reference a member of a structure by using a string variable. Here's an example of what i'm talking about:

[Code]....

Now, I know that you would usually reference the value in any of the members by using the following (String1 in this case)

[Code]....

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May 23, 2010

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Structure ID
dim CardType as string
im CardCode as string

[code]......

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Oct 12, 2010

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Mar 11, 2010

hello
I would like to know if it is possible to store an array within a structure. For examples for recording people with more than one name. Like this:

Structure Product_Reccord
Dim PNames(3) as string
end structure
It is giving me an error, help please!!

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Sep 12, 2011

I have two structrures

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Dim Count As UInteger
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Jun 27, 2011

This is my structure...
<Serializable()> _
Public Class AcctRecords
Public Amount() As Long
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[Code] .....

This is where I try to create a new instance but I get an error that states:
Overload Resolution Failed Because No Accessible "NEW" accepts this number of ArgumentsPrivate Sub FixMasterArraySize(ByVal Cnt As Integer)
ReDim Preserve Acct.Master(Cnt)
For I As Integer = 0 To Acct.Master.Length - 1
Acct.Master(I).AcctType =
New String
Next
End Sub

If Acct.Master(I).AcctType was a Boolean type there would be no error..

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Jul 13, 2010

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Now when the user selects the Submit button I want to call the Save method inside the usercontrol of the Form as each form will have a separate Save. So when I try this code snippet I get the Null reference error. Do let me know how to resolve it.

Private UCDynamic As UserControl

Then on Page Load event I use this code

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
If not Me.IsPostBack
UCDynamic = LoadControl("Controls/BkCode.ascx")
Me.PlaceHolderForm.Controls.Add(UCDynamic)
End if

Then on the ButtonClick Event for Submit I do this

Protected Sub Save_OnClick(ByVal sender As Object, ByVal e As EventArgs)
Save()
End Sub

[code]....

Thats where I get the cast Null reference error. So is it that after post back the control no longer exist on the page.

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May 2, 2011

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How would I go about making the error handling work (i.e. not crashing the program when an invalid input is made)?Also, a big change I would like to make would be for it to copy the folder structure and all files in the original folder (At the moment, it only copies files that are directly in the original folder, not files that are in folders inside the original folder).

[Code]...

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Nov 7, 2011

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[Code]...

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Dec 20, 2010

I'm working with a class that inherits the XElement class.The new class is called MXElement.It adds some new functionality to it for navigating through the XML tree, as well as some more information regarding attributes, but that's not particularly important.My problem is that I have an XML Tree filled with XElement objects.However, when I create a new MXElement object from the XElement object before, it is just a copy of that object. This means that any changes that I make to this object will not effect the original tree.I suppose what I'm asking for is a way to build in the functionality for my MXElement class and keep references to the original XElement objects.If possible, I would really prefer to keep MXElement a child class instead of building a lot of extension methods for XElement.

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Jul 23, 2009

I have to create an array of structure type in VB.net. but I am getting error while marshaling this error. I have to pass this array of structure type in to Dll function.
Code:
Structure declaration:
<StructLayout(LayoutKind.Sequential, CharSet:=CharSet.Ansi)> _
Public Structure dx_entry
<MarshalAs(UnmanagedType.ByValTStr, SizeConst:=10)> _
Public dx As String
[Code] .....

I am getting the following error:
An unhandled exception of type 'System.ArgumentException' occurred in Audit_Demo_2307.exe
Additional information: Type dx_entry[] can not be marshaled as an unmanaged structure; no meaningful size or offset can be computed.

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[Code]...

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Feb 12, 2009

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Jan 4, 2010

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Imports System.Xml
Public Class frmuseradmin

[code]......

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[Code]...

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Public element2 as integer
Public element3 as boolean

[code]...

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[code].....

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Aug 11, 2010

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[code].....

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vb
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Public ReadOnly Property Groups As IdentityReferenceCollection
Get
Dim irc As IdentityReferenceCollection

[Code].....

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[code]....

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[code]....

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[Code]....

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For rowIndex = 0 To dgvVisit.RowCount - 2
MessageBox.Show(dgvVisit.Rows(rowIndex).Cells("CoPayCharge").Value.ToString)
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Dim ClosingMsg As String
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