Structure Inside Another Structure Receives Null Reference Error?Jan 5, 2012
Public Structure structure1
Public TRANS() As structure2
Public Structure structure2
Public X() As Integer
Public Structure structure1
Public TRANS() As structure2
Public Structure structure2
Public X() As Integer
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.
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
I'm trying to create a structure and inside it put an array of "Genres". This is my structure declaration:
Dim strGenres() As String
But I keep getting an error with the .strGenres(5). VB is telling me "End of statement expected"
I'm experiencing a problem with the following c-structure:
typedef struct tagTEXTUREPROP
The Marshal.SizeOf obviously calculates a size of 76 and it works with the DLL function, but it leaves me with some bad feelings.
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 version="1.0" encoding="utf-8"?>
<artists xmlns:opensearch="http://a9.com/-/spec/opensearch/1.1/" xmlns="http://www.spotify.com/ns/music/1">
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
Now it is
At least, this is my understanding of it. It seems awkward to have to do this for such a simple scenario, so is it possible give enums properties, yet still have them treated as before? I've thought maybe I need to create a new valuetype from scratch, but I've never done that before.
In what situtations is it best to use reference arguments to return values?
Sub Example(byref value as integer)
value = 3
In what situations is it best to return the value (perhaps in a structure for more complex types)?
Function Example() as integer
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?View 1 Replies View Related
I have problems with array of structures.my structures are like this
and then I created many array of structures, like this private arrayorder (100) as order
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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.View 6 Replies View Related
, 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:
Now, I know that you would usually reference the value in any of the members by using the following (String1 in this case)
I want to make a structure within a structure. Basically it will appear like this:
dim CardType as string
im CardCode as string
In Vb.net I am trying to assign an array of structure to another array of same structure[code]...View 2 Replies View Related
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:
Dim PNames(3) as string
It is giving me an error, help please!!
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I have two structrures
Public Structure PhoneScheduleEntries
Dim Count As UInteger
Dim PhoneSchedule() As PhoneScheduleEntry
This is my structure...
Public Class AcctRecords
Public Amount() As Long
Public DateC() As String
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
If Acct.Master(I).AcctType was a Boolean type there would be no error..
I have an app with 24 different Forms. They have some security options based on which the 5 different buttons Submit, Approve, 2nd Approve, 3rd Approve, Reject etc get enabled disabled.Now I designed a MainForm that has all the buttons and the security code for them. I have created eachform as a usercontrol and load them dynamically based on which form the user wants. My loading works perfectly fine. I load the control and Add it to the place holder in the Page load event of the main page.
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")
Then on the ButtonClick Event for Submit I do this
Protected Sub Save_OnClick(ByVal sender As Object, ByVal e As EventArgs)
Thats where I get the cast Null reference error. So is it that after post back the control no longer exist on the page.
Below is a tiny program I modified from an example Microsoft code tutorial. This program simply copies .flac and .mp3 files from one specified folder to another, and if the file is already there it simply does not copy the file. I would like to make 2 changes to the program:
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).
I'm a beginner when it comes to Visual Basic coding and I need some help with an error I'm getting. I'm trying to pass a structure array to a function to figure out a student's grade. I'm getting the error that 'QuizOne' is not a member of System.Array. Here is my code:
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.View 1 Replies View Related
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.
<StructLayout(LayoutKind.Sequential, CharSet:=CharSet.Ansi)> _
Public Structure dx_entry
<MarshalAs(UnmanagedType.ByValTStr, SizeConst:=10)> _
Public dx As String
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.
I have a structure named StudentData, it consists of a studentname, an array of testscoresand the student average. There is also an array of structure objects for a total of 6 students. I have the header, column heads, the student names and the averages printing when I click the print page event. I have tried multiple ways of setting this up to get the test scores to print, these are the structure array variables. When I put in the code to process the arrays testscores, I receive a run time error that I don't understandView 2 Replies View Related
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Public Class frmuseradmin
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I am testing a program, and I am getting a null reference error at this line. oParent.Invoke(oParent.cUpdatingSolidWorks, iSolidWorksItem). I have stepped through the program, and all the items are created. A watch window with the three objects all have data in them. I am wondering what would cause this error if the objects exist. [Code]View 5 Replies View Related
I want to be able to reference an element in an array of structures by the name of the element in a visual basic 2010 function. For example
Public Structure myStruct
Public element1 as string
Public element2 as integer
Public element3 as boolean
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Public Class Form1
Dim int As Integer = 0
Dim CustomerTable As New DataTable
Dim instance As New InvalidOperationException()
This is the code this exception occurs when i click on the home button of my webbrowser.or i enter any site on the combobox.
I have searched for two weeks, every night, exhaustively reading forum threads and trying all suggested solutions no matter how outlandish. Just as is the case with the many many forum threads about this same issue, the site works fine on my development machine. It deploys with no errors. It works from the production server and reads data from the database, but when it attempts to access a profile it crashes with this error.
A number of posts say to check or uncheck an option called "remove app_code.compiled file" but apparently this was a Visual Studio 2005 option. It is nowhere to be found in Visual Studio 2010. A number of posts say to make sure the App_Code.dll is present in my bin directory. It is present. I've deleted the app_code.compile file manually to see if that made any difference. I've changed the target framework from 4.0 to 2.0 and 3.5. I've completely deleted the site in IIS, created a different folder with a different name and redeployed the site with every combination of "allow this precompiled site to be updatable" and "Use fixed naming and single page assemblies".
i've included references to System.Web.Profile and System.Web and System.Web.Profile.ProfileCommon. I've created a new, fresh website targeting .net framework v4.0 and copied that web.config file to my application and recreated my profile entries to ensure that I didn't jack anything up in the config file along the way.
i have the following code but when i select button1 i get the following error: Null Reference Exception was unhandled-object reference not set to an instance of an object. - any idea's how to fix it ?i have underlined the line of code that is highlighted when the error occurs
Public Class Form1
Dim Ping As Net.NetworkInformation.Ping
I am getting a "null reference exception" error when I run my application, this error occurs even before the webbrowser has navigated anywhere. Why would I get this error without a webbrowser document complete occurring?
Dim HTML As String = WebBrowser2.Document.Body.InnerHtml.ToString
If HTML.Contains("Submit Comment") Then EnterData() Else NextURL()
I don't understand why I would get this error when I haven't even navigated anywhere? Forgot to say that this code is inside WebBrowser2 document_complete.
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Background: I wrote code that will output all the currently logged in User's Active Directory group names. I want the group name (ex: Acomp_user_BIG) via IdentityReference.Translate instead of the current user's SID's (ex: S-1-5-32-544) returned via IdentityReference.Value.
Here is code that I used:
Public ReadOnly Property Groups As IdentityReferenceCollection
Dim irc As IdentityReferenceCollection
I explain what I would do immediately:I have to extract data from a table using html htmlAgility Pack This 'my code that when executed gives me' a reference error.I can not figure out what is wrong, I am more 'I can not do this
a Private Sub Button5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button5.Click
Dim web As New HtmlAgilityPack.HtmlWeb()
Dim doc As New HtmlAgilityPack.HtmlDocument()
doc = web.Load("http://www.mia_pagina")
Due to this error I am getting a default date 1/1/1900. Variable 'dr' and 'dr1' is used before it has been assigned a value. Here's the code:-
I am trying not to become intimidated or give up.I created a simple database and added stored procedures to read the data on a Windows form using Visual Basic in VS 2010.First I tried the Data Grid Example and all worked, I was able to view the data using a connection string to call the Stored procedure.I have stepped it up a notch by trying to bind data to form controls and I am getting this error message when I try to navigate through the data.
System.NullReferenceException was unhandled
I have a module and form. Module has a structure.
Actually values are not stored in that array list permanently. its storing temporarily and then destroying. i want to store that values in that arraylist permanently.
I have created a structure with the following elements:
<StructLayout(LayoutKind.Sequential)> Public Structure person
Public userid As Integer
Public age As Integer
I am trying to write this structure using the following lines of code:
Sub testwrite(ByVal filename as string)
Dim temp as new person
Using mmf = MemoryMappedFile.CreateFromFile(filename, System.IO.FileMode.OpenOrCreate, "test", 1000)
However, every time I try and run the program I get the following error: "The specified Type must be a structure containing no references."I thought the "MarshalAs" created the array within the structure and therefore wasn't a reference. Can someone tell me how to get round this problem so that I can pass an array.
I have a fairly simple piece of code:
Private _PurchaseDelivery as PurchaseDelivery
Protected Overrides Sub InsertItem(ByVal index As Integer, ByVal item As PurchaseDeliveryItem)
Which is inside a class which overrides a custom list base. The code is occassionaly throwing an unhandled exception, System.NullReferenceException, on this line when used in production:
If _PurchaseDelivery IsNot Nothing AndAlso _PurchaseDelivery.DefaultSKUBinID.HasValue Then
DeafultSKUBinID is declared as an Integer? (Nullable Int) in the PurchaseDelivery class. I cannot see what might be causing this error, why would this be returning an error?
I tried adding a loop inside this loop but continue to get the error "Null reference exception was unhandled" before the loop ends.
For rowIndex = 0 To dgvVisit.RowCount - 2
For rowIndex1 = 0 To dgvPayment.RowCount - 2
n my project i am to enter a name and a test mark into two separate text boxes and then select the button to store the information into the arrays, one array for names and another for marks, but when it is reset using the Erase <Array> fuction andi try to re enter information, no matter what information is entered i get a "Null Reference Exception Unhandled" Error.I am using Visual Basic 2008.My code is as it says from now:
Public Class frmAdverageTestMarkCalculator
Dim ClosingMsg As String
Dim Closingtitle As String
I'm not sure why, but my database receieves a syntax error when I update it. If anyone can explain to me where I am doing something wrong, let me know! I'm not the best programmer, but I am doing my best