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.
<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
[Code]...
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.
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 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.
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?
I see some functions within some code that are:
Public Function GetDataObjects(Of Customer)(ByVal dataset as DataSet)
...
End Function
What exactly does the (Of Customer) do in this instance or mean?
[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.
View 8 RepliesByRef (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.
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.
View 2 RepliesI 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.
wads the difference between OptionalByVal and ByVal??how are they used?
View 3 RepliesI 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)
In vb.net the methods have their parameters using ByVal by default, it's better practice / common practice to make it explicit?
For example:
With ByVal:
Private Sub MySub(ByVal Q As String)
{
}
End Sub
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!
View 5 RepliesPrivate Declare Function ReadProcessMemory Lib "kernel32" Alias "ReadProcessMemory" (ByVal hProcess As Integer, ByVal lpBaseAddress As Integer, ByRef lpBuffer As Integer, ByVal nSize As Integer, ByRef lpNumberOfBytesWritten As Integer) As Integer
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This correctly returns the memory value as string. So yeah, now it's just the Single that's causing issues.
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]
View 4 RepliesAfter installing VS 2010 SP1 I noticed that ByVal keyword doesn't automatically appear after declaring Function or Sub parameters. Is it new feature or bug?
View 5 RepliesI 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 RepliesIf 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?
View 1 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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Code:
Option Explicit
Private Const No_ERROR = 0
Private Declare Function inet_addr Lib "wsock32.dll" (ByVal s As String) As Long
[code]...
ByVal dst As Any, ByVal src As Any-->Error: Any is not supported in declare statements i am currently using visual studio 2005.
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?
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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]...
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]...
my code as follows
[code]...
result i get here is =0.7937005259841017310542661502
where as windows calculator figure is 0.79370052598409973737585281963615