Functions Return Values As Byref Or Byval Or?
Oct 20, 2011
i have a strange issue today. Sample code is at the below of the post. The code that i have pointed out is too strange. According to my knowledge using return statement the functions return values as byval and copies the value to the stack. Also how can my class can reach outscope elements and change them. Take a look at to the code below. How this could be?
code
Public Class Form1
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim b As New ByteClass
Dim sumArray As Long = 0
[Code]...
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Jun 9, 2011
If a function returns a private shared (static) string, or a string declared as a module level variable, is the returned a reference to the shared string's instance or a different string instance having the same value?
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Jan 18, 2012
Can a function return a value byref instead of the default byval? That is to say, allow me to directly edit the variable that it is retrieving instead of just giving me a copy of that variable.Right now I'm trying to write a function that will return, based on what the user has selected through a combobox, a particular setting (eg. My.Settings.somethingHere). I then want to be able to edit the setting directly through just calling the function. Is that at all possible?
[Code]...
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Jun 26, 2010
I want to know what are classes , objects , a namespace , subroutines,functions,methods,properties and differemce betweem byval and byref in your words.
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Nov 17, 2011
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?
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Dec 8, 2010
I'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:
[Code]...
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.
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Dec 15, 2011
In VB.Net, I have an object named WorkflowButtonEventArgs that inherits from System.EventArgs.The WorkflowButtonEventArgs class contains two ByRef Properties. These are objects that are in memory, and I do not want them duplicated or copied in any way.
Can I pass the WorkflowButtonEventArgs object ByVal in VB.Net and have it still preserve the two ByRef definitions in WorkflowButtonEventArgs?Specifically, if I pass it ByVal:
Dim e As New WorkflowButtonEventArgs e has some ByRef properties RaiseEvent SomeEventName(e) ' e is passed ByVal Will the ByRef Properties/Members in e (WorkflowButtonEventArgs class) not be copied or duplicated in memory?
Long-story-short: Can I pass e ByVal, or do I need to pass it ByRef since it contains ByRef Properties?
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May 4, 2010
[Code] What is the difference between ByRef and Byval in this function. When i call this function and debug it it shows no difference the two. Can any one explain me actually what happens.
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Feb 20, 2009
ByRef (a.k.a. By Reference) points to where the object is in the memory. Any changes made to the object sent ByRef should change the values of the original object ByVal (a.k.a. By Value) points to a copy of the object. Any changes made to the object shouldn't change anything in the original object
Let's make an example:
Private Sub FormLoad()
Dim a As String = "A"
Dim b As String = "B"
[code]...
The second messagebox shows Baaaa - Buuuu instead of the expected A - Buuuu... but why is that? Apparently ByVal and ByRef does exactly the same thing. It seems like it sends the reference to the object when using ByVal, instead of making a new object.
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Mar 27, 2012
Whenever I'm going to use a new API, I have to decide for each value whether I'm going to use byval or byref. Can someone explain me in what scenarios I should use which and why? Because lacking this knowledge kinda gives me the feeling of having no control over my code.I am aware about the other threads by people asking the same question, I have read them but its still not crystal clear for me.
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Jun 5, 2012
I have seen a few people in the past confused on the usage of ByRef & ByVal in a Function/Sub's Signature. I figured i would make a simple example that demonstrates the difference of each.
Option Strict On
Public Class Form1
Dim A As Integer = 100
[code]....
If you want something you've never had, you need to do something you've never done. If you believe something to be true, then one day you will be called upon to demonstrate that truth.
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Feb 9, 2012
I just installed Visual Studio 2010 Service pack (proposed on Windows Update), and I can see a new feature on the "intellisense" that means when I write a Function or Sub in VB.NET it doesn't auto-complete parameters with ByRef or ByVal...
1) Is there anyway that I can configure this option back to how it was before?
2) If I don't specify ByX, which one is used by default? (it seems like it is always ByRef)
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Apr 10, 2009
What is the difference between ByVal and ByRef? Please remember to mark the replies as answers if they help and unmark them if they provide no help.Welcome to the All-In-One Code Framework!
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Apr 26, 2010
ByRef vs ByVal generates errors!?I had a method that used an Object Function Foo(ByRef bar as CustomObject) as Boolean this method generated errors, because some strange .NET Runtime things changed the bar object, causing its Dispose()al.A lot of time spent to understand the thing(where the ... object is changed), until somebody replaced ByRef by ByVal and object wasn't change anymore when passing to this method.As in my case the function Foo does NOT modify the bar, shouldn't ByRef or ByVal have the same effect?[code]
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Jul 23, 2010
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
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Jul 22, 2010
Reading [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?
[Code]...
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Dec 7, 2010
Is it considered bad practice (VB.NET or any language) to code a function with both ByVal and ByRef parameters as used in my getFile function below?
Function getFile(ByVal channel As Integer, _
ByRef Filename As String, _
ByRef Filesize As String) As Integer
End Function
Dim status As Integer
[Code]...
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Mar 1, 2010
Switching Byref to Byval on method calls I have many warnings raised due to: "Implicit conversion from xxxx to yyyy in copying the value of 'ByRef' parameter zzzz back to the matching argument."
My feeling is that it would be safe to change the function parameters from byref to byval as nothing special is being done with the reference type pointers inside these methods the reference types are simply being used and I think the behaviour would be exactly the same if running with a copy a pointer rather than the original.
Another consideration is that I have two classes which inherit from a base class. The same situation is occuring in that the byref params are causing implicit casting from the base class to the narrower concrete class. Again I can't see any problems with this code running byval either.Does anyone have any tips regarding use of parameters in functions when dealing with reference types?
Some of the other things that are currently being passed around byref in my project are database connection objects i.e. OracleConnection and SqlConnection. Is there any good reason for passing these around byref?
[Code]...
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Sep 4, 2010
I have a class OrderManager, that takes a parameter of type LocalFuturesList on construction. Now.. It doesn't seem to matter if I use ByRef or ByVal here.. It still references the parent class instance of it. It also doesn't seem to matter if I type New or omit it.. Probably also because it's just an address reference. But why is it like this? And what type of objects "acts" in this way? Further I find that if I change the object in the parent class by deserializing from a file (with my method call shown), then suddenly this reference is broken in some way, so the OrderManager instance now holds Nothing I believe.If my observations are correct I see two challenges:
1. How to pass a list NOT by reference?
2. How to maintain a list reference through deserialization? [code]
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Dec 22, 2010
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
[code].....
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Jul 2, 2009
Is there a Limit to the parameters that can be passed byVal or byRef to a function or procedure in vb .net ?
[URL]
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Jun 23, 2009
I have a 3rd party (c#) class that raises an event. on accsing this event i want to copy the image property to a queue.
Dim myQ as queue
Private Sub imageprocessor_NewImage() handles camera.NewImage
myQ.Enqueue(imageprocessor.currentimage)
End Sub
But when I view myQ at a later date it tells me the parameters of the images are not valid.Is it adding them by reference?i would have through adding an object to a queue was byval. how can i enforce this?
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Apr 7, 2010
I started this tutorial on sub procedures and am having trouble trying to get this program to execute properly. The problem lies with the total. I am trying to figure out the math part of it. When I hit F5 I can see this
Item Quantity Price.
Pizza Slices
Fries
Soft Drinks
Total
But I can't get them to add up and display the quantity and price. I tried the ByVal and ByRef code but am not sure if I did it right
Here is the code that I have so far:
Public Class Form1
Private Sub btnCompute_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCompute.Click
Dim pizza, fries, drinks, total As Double
[CODE]...
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Apr 4, 2011
In this application I need to allow users to enter a month as integer (1-12) then use integer tryparse to validate that input, that seems to be the easy part. I need two create two functions, one that returns the name of the month and the other returns the number of days in that month. The arrays are supposed to be defined and initialized within the function so that the main program can take the user input and call the two functions, then return the appropriate values as output to labels. I am not sure how to declare the arrays in their appropriate functions and then how to call those functions to retrieve the right value from the function.
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Mar 16, 2009
Sounds simple enough, but its not working. In this example, I want to set the values of 3 fields to equal a 4th. I could do something like this..[code]...
Values in the param array did not get updated in the return! I was expecting to have all of the final values now be "1", like they are in the Function.
Is there any way to get an update-able ParamArray collection like this? ParamArray must be declared ByVal, but with a reference type like String, shouldn't that only make a copy of the pointer and allow me to change the underlying value?
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Jun 12, 2009
<script runat ="server" >
Dim objDT As New System.Data.DataTable
Dim objDR As System.Data.DataRow
[code]......
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Jan 9, 2012
I have functions in my program that stop after it reaches a Return line but I need the function to continue in case what I want the function to return changes. Is there a workaround for this or a way to force the function to continue after a return?
I made a Test Program to demonstrate the problem. It is a Form that contains only a button.
Here is the source code:
[Code]...
The messagebox always says "It returned False" when if it continued going through the code like I want it to it would have returned true.
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Dec 19, 2011
Currently I have been writing subroutines in a activex dll to carry out functions in my main program but I have hit a little snag when trying to return a function when an if statement is triggered. What I want to do is for the dll to check if a function in the my.settings of the main program is true/false and if it turns out that it is true/false in the settings it will trigger the if statement in the dll which will then send data back to the main program - seem simple? I am also wondering, can you transfur boolean settings for enabled textboxes through functions stated in the subroutine of the dll?
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May 17, 2009
In C#, when writing a function that returns an IEnumerble<>, you can use yield return to return a single item of the enumeration and yield break; to signify no remaining items. What is the VB.NET syntax for doing the same thing?
[Code]...
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Jun 10, 2011
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?
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