I have an old unmanaged dll function and I want to pass an array to it.The dll function expects the array to be passed by reference.Sometimes I can do that and sometimes I need to pass a pointer in a variable.Is it possible to override the declare for the function so that I could pass either the array by ref, or a pointer to it if I need to?
View 15 RepliesI'm still working on the code in this thread [URL] and as I mentioned in that thread, I thought that passing objects around between methods would probably be bad for performance (perhaps not really noticeably at first but maybe if I did it enough then it could have an impact).
1. When you pass a reference type to a method using ByVal then what is actually 'copied' ? I understand that ByVal copies the object into the local method that you are calling where as ByRef passes a reference to the actual object so you can work with the original object. So when you have a Reference type and you pass this ByVal then does copy the entire object or does it just copy a 'reference' to the object?
2. When working with an object that relates to a 'physical' item, such as a file on disk or a network stream between two connected machines, then what happens when you pass it around between methods (this might be irrelevant depending on the answer to the first question) ? I mean if I have a NetworkStream object that represents the data stream coming from a remote computer, if I then pass that ByVal into another method then does that mean I am still working with the same data stream or a copy of it or what?
I have been working on this for a few days, and I am going around in circles. I can make the program work by including everything in the same sub procedure, but the assignment requires that I do certain tasks by using function procedures.What I need to do is take the contents of a text box, reverse the order of the first and last names, and add them to a list box. I can do that, just not by passing value from a function procedure. Here is my
View 4 RepliesReading [URL] made me wonder whether the comments in there did apply to Strings in terms of performance. Since strings are copied before being passed, isn't it much more efficient (if the callee doesn't need a copy of string course) to pass strings ByRef?
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I have some code that is transforming the coordinates of a line.I want to keep the original coords and I thought passing the line ByVal would be the best way.The original VB6 code used a temporary variable so that the original coords were not updated.I'm confused as when the X & y coords of 'line' are changed 'MyLine' is also changed. I had assumed only 'line' would change and 'MyLine' would remain unchanged'.
Private Sub TransformSaveLine(ByVal MyLine As LineType)
Dim P As Integer
Dim line As LineType
Dim x As Double
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have a subroutine which parameter is an array like below:
Private Sub DoubleArrayValues(ByVal arr() As Integer)
Double the values.
[code].....
I know strings are immutable, so the minute you change a string reference's value .NET makes a brand new string on the heap. But what if you don't change the value of a string reference; rather, you simply pass it into a function ByVal -- does this operation copy the string value on the heap as well? My inclination is "no," but I'd like to confirm.
For example:
Public Function IsStringHello(ByVal test As String) As Boolean
Return (String.Compare(test, "Hello") = 0)
End Function
Calling program:
Dim myWord as String = "Blah"
Dim matchesHello as Boolean = IsStringHello(myWord)
I know passing myWord by value makes a copy of the reference to "Blah", but since I have not tried to change the string itself, would it make another copy of the string on the heap?
In VB.NET, can we pass an original object as an argument without instantiating it? For example, I have two forms in my project formA and formB. Now I have this code.
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Apart from this, in VB.NET in any class like formA, if I type formA, I can see all the objects and controls present there but not in C#. Again, I have to make a new instance to see all the controls. This becomes a problem if I want to manipulate two running and working instances with each other. So what basic thing am I missing here?(I am an amateur programmer migrating from VB.NET to C#. Things are going nice and clean expect for the ones I've recently figured out.)
I'm using VB.NET 2003 with .NET Framework v1.1. I know it's getting a bit old now but I'm stuck with an existing program and don't have the time/knowhow to convert it to anything newer.
My question would probably be solved very easily with Generics in .NET 2.0 but as I can't use that right now, I'd like to know if the following is possible:
I have a load of manager classes which inherit from DictionaryBase and hold collections of my custom classes. For example, I have a Employee class, a Batch class, a Supplier class, etc... and each of these has a Manager classwhich holds a collection of them - eg: my PlantTrayMgr class holds collections of PlantTrays, etc..
I have one particular form where I have to populate loads of comboboxes with the contents of various Manager objects. What I currently do in my form load event to populate comboboxes is this:
Code:
Option Strict On
Option Explicit On
Private _plantTrayMgr As PlantTrayMgr
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In my vb.net code I want to call a dll file created by Qt4.
Now everything works fine untill and unless I pass some string argument to the function.
Here is the function in dll file:
const char* QtEngineDll::randInt(char url[])
{
QString result;
/*QTextCodec *codec = QTextCodec::codecForName("UTF-8");
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When the function returns some constant value, say if i put result = "Abhijit" then it returns the value properly. But if I want result to return value url the it is returning some garbage values.
I have a DLL written in fortran that I know works because I am getting it from a working software package that we use daily. I am trying to call it from anything but am having problems i believe with passing the correctly formatted arguments in and out of it, so i decided to try and access it from a VB program. I chose VB because I have contacted the developer of the software package we are using and he gave me his DLL function call in VB6, even though he is not allowed to show me the FORTRAN source.
Problem is (perhaps, i think) that I am writing in VB.NET, which has different data types than VB6. Can anyone see why i am am having problems. The error i get upon running is: "AccessViolationException was unhandled: Attempted to read or write protected memory. This is often an indication that other memory is corrupt."
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I'm designing an interface using visual basic .NET with visual studio tool. In my program I have to call an extern .exe using the function shell() and pass a FileName to it. The problem is that what it passes to the executable is never the file path. My code is this one and I think it should work but I don't know why, it doesn't.
Public Class FormMain
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
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When I try to do the same in .net the "array argument" value of the second sub is either Nothing or I get an error saying "Value of type 'String' cannot be converted to'System.Array'."I've tried converting the array to a system.array but it will not hold all the Types of data it needs to hold. (I tried 3 days ago and don't remember what Types would cause an error. My 1st value is a string and the second is an integer and this caused some error.)
View 1 RepliesI have written an application to register a url type extension at startup so in short if user inputs dld:// in any browser it loads my app now, what I want to do I want to somehow move a bit further like if user goes dld://about the application loads and shows the about page
View 5 Repliesis there a way i can do like this in vb.net
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what i want is that idx keeps incrementing after each line, without incrementing it on a seperate line.
I am a beginner using Visual Studio Express 2010 to create a small console app to use as a utility accompanying another primary app that can pass a command line to the utility. I would like to set it up so that the utility will not run independently but only run and load its only form (Form1) if it is launched by the primary app using a "/run" command line parameter. (I can set up the primary app to launch and pass a command line parameter. I need help with the utility's code.)
The utility already has some VB code, so I need to figure out what code to add to receive and act on the " /run" command line and even more challenging for me, where to place this new code so it works.
pseudo-code:
initial event to read the command line, then if it is " /run" load Form1, else do not open and run utility app.
my current solution as you can see is by using shared variable within a class in order to pass a value.
on the form load of my application i called: workerSample.RunWorkerAsync
Dim finalList As List(Of String)
Private Sub workerSample_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles workerSample.DoWork
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Im trying to pass a array as a argument to a Javascript function from code behind(vb.net)
Code im trying
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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.
View 1 RepliesVB.NET is not letting me dance with both feet, or piss with both hands. I've got one foot and one arm tied behind my back at every turn. I want to use this statement in a function:
Return CType(Formatter.Deserialize(FS), DS)
Seems doable, right?
Function ReadFileStream(ByRef FS As FileStream, ByRef DS As Object)
Dim Formatter As New BinaryFormatter
FS.Position = 0
Return CType(Formatter.Deserialize(FS), DS)
End Function
Right? I mean, CType only accepts a class name as the second argument. I can't give it an instance of a class, or it croaks. Yet if I try to pass the class name as the argument to that function:
DataInfo = ReadFileStream(FileStream1, DataStruct)
VB.NET croaks on this, too, complaining that "'DataStruct' is a type and cannot be used as an expression.". It's used as an expression by CType just fine outside of the function. Does the VB.NET legislature provide a clause that allows for a 'Type' to be passed as an argument in a function? Writing all the supporting code ten million times to deserialize a file using CType ten million times in a large application will get very complicated and tricky very quickly. It should be handled by a routine so that any cases and adjustments that come up can be dealt with in one spot.
I have a class and method exposed to a client asp.net app. The class looks like
<DataContract()> _
Public Class Class1
Private v_string As String
Private v_integer As Integer
[code]....
The method is declared as
<OperationContract()> _
Function GetStuff(ByVal bar As Class1) As String
In the client code I create an instance of Class1 and set the values for v_string and v_integer, but using Wireshark to look at the xml being sent to the server only a value for v_string is being sent as part of Class1. I'm guessing this is because it considers the value of v_integer to be null/not set. Here is an example of the client code.
Dim MyService as New Service1.ServiceClient
Dim test as New Service1.Class1
test.P_integer = 1
[code]....
how different types are passed/used since Integer is a intergral type and String is a class, but can't seem to work out what to do to fix the problem.
<script runat ="server" >
Dim objDT As New System.Data.DataTable
Dim objDR As System.Data.DataRow
[code]......
Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged
Textbox1 how the text box by real-time data monitoring?
I'm making this program that opens the same forder in every pc but it identifies the pc name to do it.
Public Class cv7import Private Sub cv7import_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
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but I want it to do it with the pc's name and I'm not sure how the environment.systemdirectory works, or even if it's the right one to use. Is it the right thing to use or is there a better solution.
I have the following VB function which takes a FileInfo object as a parameter:
Public Shared Shadows Sub Start(ByVal filePath As FieldInfo)
XmlConfigurator.ConfigureAndWatch(New System.IO.FileInfo(filePath.ToString()))
End Sub
In another class I have the following code calling that 'Start' method. But VisStudio indicates there is a problem with the 'FilePath' argument that I'm passing.
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Just as a secondary question, usually I reduce: -(ByVal sender As System.Object, ByVal e As System.EventArgs) to just () for most occurrences of auto-generated subroutines. Is there any harm in doing this? I cant see any reduction in performance but do get more readability.
View 8 RepliesI made this procedure re-use a select query:
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And I use it like this if I would want the selected value placed in a textbox and it works fine
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However if I want the value to be passed in a string like so:
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The string ends up having an empty string value. How do I assign the value I queried to that String?
As I understand it, C# passes parameters into methods by reference. In vb.net, you can specify this with ByVal and ByRef. The default is ByVal.
Is this for compatibility with vb6, or is it just random? Also, how can I specify what to use in C#? I kind of like the idea of passing parameters by value.
I am a student and i get confused when i see a lot of ByRef and ByVal arguments in a sub procedure. Can someone make it simple for me to understand when it should be used?
View 9 RepliesI've read a lot on this, but am having a hard time thinking through this tonight. (Maybe it's the hydrocodone... just had a root canal. i'm just starting on a class to handle client connections to a TCP server. Here is the code I've written thus far:
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Now, on my Socket property, when setting the value, it is required to be ByVal. It is my understanding that the instance in memory is copied, and this new instance is passed to value, and my code sets _Socket to reference this instance in memory. Yes?
If this is true, then I can't see why I would want to use properties for anything but native types. I'd imagine there can be quite a performance hit if copying class instances with lots of members. Also, for this code in particular, I'd imagine a copied socket instance wouldn't really work, but I haven't tested it yet.