Deep Copy - Is Object Returned By Reference From Function ?
Aug 5, 2011
If I instantiate an object within a function in VB.NET and return it, does it return it be reference or by value. IE - should I be worried about performance if I write something like this:
Public Function ret_obj_func() As big_object
Dim ret_obj As New big_obj(<lots of stuff>)
Return ret_obj
End Function
If I call this function from somewhere else, will it instantiate the object in the ret_obj and then create a deep copy to pass back a copy to the caller, Or will it just pass back a reference?
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Aug 5, 2011
This should be a fairly common question, but I haven't found a straightforward answer anywhere.
If I instantiate an object within a function in VB.NET and return it, does it return it be reference or by value. IE - should I be worried about performance if I write something like this:
Public Function ret_obj_func() As big_object
Dim ret_obj As New big_obj(<lots of stuff>)
Return ret_obj
End Function
If I call this function from somewhere else, will it instantiate the object in the ret_obj and then create a deep copy to pass back a copy to the caller, Or will it just pass back a reference?
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Apr 27, 2009
Essentially what I want to do is copy a WebBrowser object such that I can do the equivalent of "Open In New Tab" or "Open In New Window" actions, maintaining any posted data. I don't just want to navigate to the same URL as in the original WebBrowser object, rather I want to repeat the HttpWebRequest.
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Feb 1, 2012
In VB.net, when I retrieve a value from a list do I get a copy of that value or a reference to it?
dim blah as someObject
dim listOfBlahs as list(of someObject)
listOfBlah.add(new someObject(1))
[Code]....
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Dec 1, 2010
As I understand it a shallow copy is like a CLONE copy of an object where the values for each property are independent of one another whereas a DEEP copy is a copy that uses the same memory locations and therefore if you change a value in one it is also shown in the second item ( By Reference to the same memory locations ).So my main question is, when dealing with CLASSEs, STRUCTUREs etcetera containing REFERENCE types.is there anyway to quickly create a CLONE or shallow copy of an OBJECT or not ? The only way I can think of is to put the item into a one dimensional array and use the CLONE method for an array. [code]
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Dec 1, 2011
I am working on a application that has quite a few functions involved and have been thinking of the following: If I have a function that has a few paramaters, is it more efficient to pass the objects to the function(Example 1) or reference the objects in the parent(Example 2)? Does it matter if the objects are large or not?
Example:
Class mainform
Public myGenericList As New List(Of String)
Public myDatarowArray() As DataRow
[Code].....
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Jan 31, 2010
Is there any way possible to deep copy a Control? Just want to know if its possible
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Jun 13, 2012
I call the function GetDataTable and when it gets to the return line, I get the error message: Object reference not set to an instance of an object.
Dim DB As New DBConn
Dim gd As New DataAccess.GetData
Dim DT As New DataTable
[Code].....
Updated. I'll see if I can update with the DataAccess.GetData code. I didn't originally put it in there because our shop use it all the time and have no issues with it.
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Jan 20, 2010
I have created a form with a tab control that I want to be able to make a copy of in such a way that all the child controls and their data are copied as well. I have tried this:
Dim NewPage as TabPage = tcViews.TabPages.Item(0)
tcViews.TabPages.Add(NewPage)
I end up with a reference to the first page. That is, if I change something in the old page, it changes in the new one as well. I believe this is because VB.NET treats assignments of classes as references, rather than values. Hence only the memory address of the original is copied, so essentially both refer to the same tab page in memory. I also tried serialization and deserialization.
The TabPage is apparently not serializable. And I heard about MemberwiseClone, but it isn't accessible, according to Visual Studio. There doesn't appear to be a Clone method available either. How do I make a new tab page that is totally independent of the original, but that has copies of the original page's controls and their property data, which can then be edited independently of the originals?
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Mar 27, 2009
i have a user define object which i'm initializing with data from external datafiles.... the purpose of this object is to reduce the amount of disk/data access and processing required every time i need to add an instance of this object to a collection.so, whenever i add a copy of this object to a collection, i would simply reference the "base" object, and avoid having to process all the data and perform the conversion and so on...the issue is when i add the object
Collection.add(Base_Object, Key)
the collection ITEM is a Reference to the base object and not a copy.
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Aug 15, 2006
If I have a generic.list(of ClassA), is there a simple way to create a deep copy of this list that will not affect the original copy? It seems to work if I have a generic list of Structures, but for some reason the copy constructor for lists of classes only copies pointers to the elements (or maybe a pointer to the whole list?). I would move to structures if it were not for the fact that I can't find a way to edit the members in the structs in the list. eg:list(0).a = 5 'Does not workIs there some way to get around this without declaring an instance of that structure, like this:dim str as StructA = list(0)str.a = 5I'd
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Feb 6, 2012
I am trying to make a deep copy by adding a clone property to my class.
[Code]...
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Oct 27, 2010
Following up on my question yesterday to deepcopy an object with events in C# and attach the events of the original object to the Cloned copy is pretty easy, you just set the Event declaration in the Copy = the value in the original. Deep Clone when events are attached. How do you do this in VB.Net? (Using .Net 2). Maybe there was something with reflection where you can examine what events are bound and somehow transfer those to the new object.
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Apr 18, 2012
I have an object (a third component gridview) which is serializable, and I need a deep clone of this object. I have the following code which throws the exception."The type System.Windows.Forms.Control in assembly System.Windows.Forms, Version=2.0.0.0, Culture=neutral, PublicKey Token=b77a5c5 61934e089 is not serializable".So the gridview's base class is System.Windows.Forms.Control, which is not serializable. How can I get a deep clone from the gridview? [code]
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Jan 28, 2010
I have a DLL that is written in C++. the functions of the DLL have parameters defined as unsigned char:
apiStatus __declspec(dllexport) __stdcall Gen2Read(HANDLE
hCom,unsigned char Membank,unsigned char WordPtr,unsigned char WordCnt, unsigned char *value, unsigned char ReaderAddr );
I have tried
<DllImport("Mr915ApiV10.dll", CharSet:=CharSet.Auto)> _
Public Function Gen2Read(ByVal hComHandle As IntPtr, ByVal Membank As Byte, ByVal WordPtr As Byte, ByVal WordCnt As Byte, ByRef value As IntPtr, ByVal ReaderAddr As Byte) As Integer
End Function
And the call:
Gen2Read(hComHandle, membank, wordptr, wordcnt, value, m_ReaderAddres)
In the original code in c + + value is: unsigned char buf [40]. And I'm not able to convert the value returned by reference into Byte ().
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Feb 26, 2011
I'm trying to re-write an old VB 6 OCX into a VB.net DLL and I'm having problems accessing the object returned from a COM object. Here is a snippet of the old VB 6 code: Dim objResult as Object
[Code]....
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Jan 26, 2010
Can I reference a dll programatically in VB.net? Or change the Local Copy path for a dll reference?
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Feb 6, 2011
When I query a DataTable using LINQ, are the rows returned as references? Either way, is it possible to control this behaviour, so that rows are either returned as references or as new rows?My guess is that all objects are returned as references by default, since that seems to be the normal behaviour in most programming languages.
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Mar 17, 2012
The book "Beginning ASP .NET 4 in VB 2010" contains the following:NOTE: TaxableProduct inherits from Product.You can also cast in the reverse directionfor example, cast a Productreference to a TaxableProduct reference. The trick here is that this
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Aug 26, 2011
I have this bit of code
Private Sub SpellChkMenuItem_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles SpellChkMenuItem.Click
Dim activeRichTextBox = TryCast(Me.ActiveControl, RichTextBox)
'clsFS.CheckSpelling(activeRichTextBox)[code]....
When I am in the rtb and click on spell check button it tells me the error "Object reference not set to an instance of an object." On this line
SpellChecker.Text = activeRichTextBox.Text
But it is suppose to be getting the focused rtb correct? So why is it not referenced
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Apr 4, 2012
How to give another function's returned value in LINQ.[code]but in above query I should write code to store the return value of GetObjProperty Value(p) and add obj-p and returnValue combination to the dictionary.The last line below code is wrong. but please suggest me how to correct it. My intention is, I want output collection(say dictionary) of each fruitname and its color(returned by other function call) for all the fruits which the GetFruitColor is not nothing(it can be empty or valid string).[code]In above code last line is wrong. So how to put getFruitColor in k, how to correct it to save the k value and give me output as dictionary of fruit and k value.
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Sep 5, 2010
Why this code doesn't work? It returns an unexpected value actually total = 0.
total = Cscore(TextBox1.Text) * CDbl(TextBox2.Text)
When trying this
total = TextBox1.Text * TextBox2.Text
It returns the expected value but I need to pass textbox1.text to the function to get the desirable value
The function is this
Public Function Cscore(ByVal score As Integer) As Double
Select Case score
Case score = 100
Return 5.0
Case score >= 95
[Code] .....
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Apr 2, 2011
I have many functions that perform mathematical calculations.
Here is one for example:
Public Function internaldiamofcasingpipecalculation(ByVal Externaldiameterofcarrierpipe As Double, ByVal insulationthickness As Double) As Double
[Code]....
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Feb 22, 2010
I'm new to VB.NET and want to parameterise the SQL Connection Strings in my VB.NET App. I've added a function to my Main Form to retrieve the App.config File like:
Imports System.Configuration
Imports System.Configuration.ConfigurationSettings
Public Class MainMenu [code]....
In my other forms when i want to reference the Connection String, i get an error saying getConnStr is not declared?
Private Sub UpdDept_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Try
myconnection = New SqlConnection(getConnStr()) <=============
Dim mycommand As New SqlCommand()
why i get this when i've declared the Function as Public?
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Mar 18, 2009
When the AlertsSettings.xml is not present the Appsettings is assigned to nothing. The variables that follow that definition rely on the existance of that information which will normally be set by the load method. But when there is a problem and either of the variables do not get a value how do I handle that in the code that relies on those values. The Settings class deserializes an xml document and assigned values to properties.
Sub Main()
Dim Appsettings As Settings = Settings.Load("AlertsSettings.xml")
Dim AlertsServer As String
[Code].....
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Nov 28, 2010
I am receiving this error: Reference to a non-shared member requires an object reference on the code I've
bolded within the code body. Here is my code:
[Code]...
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May 8, 2010
I get this error:Reference to a non-shared member requires an object reference.When i compile on the following code section:
Private Sub statusBarToolStripMenuItem_Click(ByVal sender As Object, ByVal e As EventArgs)
ToolStripMenuItem.Checked = Not ToolStripMenuItem.Checked
statusStrip1.Visible = ToolStripMenuItem.Checked
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Jun 20, 2011
when I do something like this: Process.Start [URL] it says that error only on Form2 not Form1.
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Jul 23, 2009
Error 'Reference to a non-shared member requires an object reference'?I want to know what a non-shared member is.
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Dec 7, 2010
I am opening frmB (variable for FormB - the actual form) from frmA. From btn1 I open frmB like this:
frmB = New FormB()
frmB.Show()
From btn2 (frmB is already open) I bring frmB to the front from behind frmA:
FormB.Show()
FormB.BringToFront().
No problem so far. Now I need to pass an arg to frmB. This is where I am having the problem.
from btn1 (in frmA) I do this:
frmB = New FormB(myArg) '--pass myArg to constructor of FormB -- no problem here
frmB.Show()
then from btn2 -- this is where I have the problem
FormB.Show()
FormB.BringToFront()
I tried placing myArg in FormB.Show(myArg) but that did not fix the problem. What is the correct way to pass myArg to FormB (frmB) in this scenario? Do I need to share FormB or frmB? How do I do this? "frmB" is frmA level variable.
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