Passing A Pointer To A Structure To A C DLL?
Sep 28, 2010
Private Declare Function src_simple Lib "libsamplerate.dll" (ByVal data As IntPtr, ByVal converter_type As Integer, ByVal channels As Integer) As Integer<br/>
Private Declare Function src_strerror Lib "libsamplerate.dll" (ByVal err As Integer) As IntPtr<br/>
<br/>
<StructLayout(LayoutKind.Sequential, Pack:=1)> _
[code]....
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May 3, 2011
I am trying to use VirtualQueryEx to read the memory of a process (first instance of notepad in this case). This function returns a pointer to the MEMORY_BASIC_INFORMATION structure. I am trying to read this structure.But everytime I try to access a member of the structure, I get a zero, which indicates I am messing something up.I am copying my code here.
-Coder_in_distress
Imports System.Runtime.InteropServices
Module Module1[code].....
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Mar 12, 2012
i need to call this c++ function
HCTRegisterReceiver( &ReceiverInfo, &m_rid )
ReceiverInfo is structure
m_rid is DWORD
this is the stucture in and m_rid variable declaration in vb.net
Public Const WM_USER As Long = &H400
Public Const WM_HCTNOTIFY As Long = WM_USER + 9[code]....
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Jun 12, 2009
How can I copy from a structure to the memory referenced to by a pointer back and forth?I need to do it with an offset.
Dim g_memoryPointer As IntPtr
Dim teArgs(10) as ArgumentStructure 'a structure defined somewhere outside my prog
Dim ix as Long, offset as Long
[code].....
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Oct 28, 2009
I'm making a "wrapper" for an unmanaged DLL (written, I'm fairly certain in C). I have a c++ "wrapper" that I'm trying to convert to VB.net. I've got most of the program working, but I've hit a brick wall.
I'm trying to convert the following two structures from their c++ versions to their vb.net versions. I cannot be sure which is the problem because both must be passed at the same time. The error I am getting is thrown by the object and indicates "Invalid structure size specified". I can cause this error on other objects when I either don't set the dwSize variable, leave off a parameter or change the parameter type incorrectly. Note that the dwSize parameter is supposed to contain the size of each structure. I'm successfully calculating that for my other structures and I'm using the same method on these and the results appear correct, so I do not believe the problem is found there. The object uses a lot of structures and the rest of them are working. These two are the only ones with a) an unsigned character pointer b) an unsigned long array and c) doubles.
C++ versions:
CODE:
I don't think I'm missing any parameters - the help file seems to agree with me on this, but it's theoretically possible that there is something missing (though I don't think so for other reasons as well). My suspicion is that it's dwPalette, pImageData or pMaskData with (in my uninformed opinion) more suspicion on the pImageData and pMaskData.
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Apr 6, 2009
i'm writing an application that using a picture-box (raster image, like a map).I want to show some label when my mouse pointer passing at some area.
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Jul 30, 2011
I have a DB with ~25,000 records that I keep in memory, and I need to pass one record to a second form for display.
code snippet follows:
Structure User
Dim First As String
Dim Middle As String
Dim Last As String
[code]....
The second form opens on second screen (Dual monitor) but I'm not sure what I did is correct. I have hit a wall on how to pass the single record from the structure to the form.
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Sep 30, 2011
I have the following .dll file created and added as a reference in my calling project; however, being new to vb .net I seem to be having difficulty calling the dll that I created.I want to pass a string to the below function, break that string out into two strings and then return the structure.
Namespace Item_Breakout
Public Class Item_Run_Breakout
Public Structure vbItem_Code[code].....
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Feb 22, 2011
I'm migrating some VB6 code to VB.net,the code contains a structure that contains 1d arrays, 2d arrays, and few other variables.The general outline of the Vb.net structure is as under
[code]...
The call to the dll is declared as under Public Declare Sub getState Lib "val.dll" (ByRef state As Test)Elsewhere on this site I realized that we have to "marshal" the structure to allow it to be compatible with the unmanaged code that is about to accept it.However I still receiving runtime errors when running the code, I don't have any clue of how to use the System.Runtime.InteropServices.Marshal class.What would be the correct way to pass this structure to the dll?EDIT: The original VB6 data type is
[code]...
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Nov 7, 2011
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:
[Code]...
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Jun 21, 2012
I can't get to pass structure as argument through subs/functions in different files of single vbnet project like I use to in earlier MS basic versions.[code]File "mysetup.dat" is reachable and data is saved correctly what I can see with HxD.But read part seem's to not work as expected. Please any help on reliable passing structure as argument without too much public elements based on upper example.
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May 1, 2009
I am trying to figure out how to print specific members of a structure when I only have to pass the structure itself i.e.
Dim Point1 as PointF = New PointF(15,30)
Debug.Print(Point1) ' This will output "{X = 15, Y = 30}" by default
I am trying to figure out how I can do the same with my own strucutres, for example:
Dim Point2 as PointF2D = New PointF2D(15,30)
Debug.Print(Point2) ' This will output "ClassName.PointF2D.Point2"
How can I get my structures, when passed to a print statement, to print specific members of that structure by default? P.S. Please give another way other than overloading the .ToString function.
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Jul 15, 2010
I have an open source project I converted to vb.net. I solved all the errors, except for one. This is the C# line
[Code]....
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May 27, 2010
I'm having problems with marshaling in VB.NET to C++, here's the code :
In the C++ DLL :
struct APP_PARAM
{
[code].....
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Apr 7, 2010
I'm sure there are several ways of achieving my goal but I am after opinions on what you think is the best option. I'm writing a vb.net application which (amongst other thinks) interfaces with media players in the home. Because there are different types of media playersI'm trying to structure it so each type of media player has it's own class which interfaces to a management class which sits on top of all the different devices types.
The device classes are responsible for discovering the phsyical devices and returning that information up to the management class. A device class may be responsible for monitoring 1 or more physical devices so..
[Code]...
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Dec 29, 2010
How can I declare pointer to pointer in ATL. Actually I have a handle which I want to pass by address to function. As shown below
STDMETHODIMP Function(HANDLE* hHC) //HANDLE declared as void * so actual type is void **
OR
STDMETHODIMP Function(LONG **hHC)
And want to access this function from the VB client.
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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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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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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 23, 2010
I want to make a structure within a structure. Basically it will appear like this:
Structure ID
dim CardType as string
im CardCode as string
[code]......
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Oct 12, 2010
In Vb.net I am trying to assign an array of structure to another array of same structure[code]...
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May 1, 2010
I understand there are no pointers in VB.Net. I need to use something similar.The issue is that I have a structure that represent a deck of cards, with elements showing how many of each type of card there is. So I have my_deck.ace, my_deck.two, and so on.What I want to do is set a pointer called current_element that refers to any element in the structure. It may one time point to my_deck.three, and another time to my_deck.nine, and so on. It could point to any element.What I want to do is, for instance to set current_element to point to my_deck.ace, then decrementing current_element would reduce the count of aces by one.[code]that would work, but it's inelegant, I have about 30 different operations to perform, some of them using several lines of code. I'd like to avoid this if at all possible. I could tolerate doing it 2 or 3 times, but not 30.
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Oct 11, 2009
I need to change the default windows pointer to this: not generally, just in my program. (Form1) There's a Pointer Control But I Dont Know What That Does.
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Dec 10, 2009
I've got a 3rd party C application that's compiled to a non-.NET non-COM DLL. It has one simple function declared like so: Declare Function CapiTaxRoutine Lib "taxcommono.dll" (ByVal sInData As String, ByVal OutputData As String, ByVal intINPutLength As Long) As Integer
If I place the taxcommono.dll in my path (C:WindowsSystem32 is what I'm using because it's what the vendor recommends),I can wire up a call to the function and it works just fine.It returns a 1 or 0 for success/failure, but it also sets the value of the OutputData string parameter (using some C pointer magic I'm not familiar with) to a huge fixed width format return record that has the data I need.When I call it from a .NET .exe application, it works just fine.When I try to call it from an ASP.NET application via a referenced compiled .NET wrapper DLL, it runs but can't set that string.In order to get it to run, I can't have taxcommono.dll in my path, but rather have to place it in my Bin directory of the web project.Does anyone know of a reason it can set the pointer when called from an .exe application but not when called from a web app?The .NET wrapper DLL I'm using works when called from our ERP software, which is not web based. But when I add a reference to that same DLL in the web app, it won't give me that output value.am used to just getting a return value instead of a function setting the value of one of my input parameters.
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Feb 10, 2010
In VB6 I have several child forms that have Subs and Controls with the same names.I need to access these Subs and Controls from public subs (in a module) that have a reference to the Active Form.[code]...
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Nov 12, 2010
I'm by no means a good programmer and I'm just trying to wrap my head around some of this stuff, so please forgive me if this is a dumb question.I want the following to produce a message box that says "2", not "5":
Public Class SomeClass
Private SomeInt As Integer = 5
Private SomeListOfInts As New List(Of Integer)
[code].....
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Mar 30, 2009
im in a project using drag and drop events and.. , when i drag a label image, i need to change te cursor pointer from an image that is on a labelike the SO windows when you drag a file appears like a mirror with alfa minimun so its like the image but more transparent when i drag i need to change the cursor pointer from an image that i'm dragging by the way im, using visual studio .net and im programming in visual basic
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Nov 5, 2011
Public Class Form1 Public Declare Function GetModuleHandle Lib "kernel32" Alias "GetModuleHandleA" (ByVal lpModuleName As String) As IntPtr Public Declare Function GetProcAddress Lib "kernel32" Alias "GetProcAddress" (ByVal hModule As IntPtr, ByVal lpProcName As String) As IntPtr
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim hmod As IntPtr = GetModuleHandle(Nothing) 'Work Dim addrs As IntPtr = GetProcAddress(hmod , "TestFunction") 'Not work, always NULL why??
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