.NET Containers - When Are Members By Reference, Value?
Oct 25, 2009
I migrate between C++ and VB.NET in my coding ventures... which leads to the occasional confusion about when something is by value or by reference in VB.NET.Let's say for example that I have an array of MyObject which is populated with a bunch of objects.
dim MyArr(5000) of MyObject. let's say that the information from this array travels throughout various data structures:
dim MyList as new List(of MyObject)
for i as integer = 0 to 5000 step 1000
Mylist.add(MyArr(i))
next
Under the above scenario, I believe everything is by reference. If I extract an entry from "MyTable" and modify its MyObject Members, I think that the original in MyArr will be modified.However, I have run into situations where I thought something was by reference, and it was by value. Are items always added to containers by reference, or are they sometimes added by value?
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Jan 5, 2010
ok this is annoying, i've got a structure RInteger.
Private VAR_Value As Integer
Private VAR_Max As Integer
Private VAR_Min As Integer
[code]......
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Dec 17, 2011
How do I go about looping through all the controls within a container, and all the controls in the container of a containing control, and so on.
[code]...
The following only retrieves -Panel and none of the other controlsFor Each cntrl As Control In Me.Controls Next How can I retrieve them all in a For Each loop without an If/Then for every level in the stack?
[code]...
This is so far the best method I found of doing this.
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Feb 15, 2009
I want to do a container that seems like this: Wich containers must use?
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Jun 8, 2011
I was wondering if there is a way to group controls together without using any containers such as panel, group box, or container.
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Jan 31, 2010
i'm working on a program and i'm working with panels, and i'm very frustrated because I want to bring a panel to the front of the form but because of its parent it is locked into another panel.... in the properties for the panels there is no Parent container option though the only way i know how to modify parents is during runtime like this Panel1.parent = Me
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Apr 14, 2012
Been doing web development for the past 2 years - so I'm a little rusty (and I just switched to VS 2010 from 2008 so maybe something new is available)... I have 4 toolstrips floated to the top of a form. And I have a picturebox below - filling the whole form. Unfortunately the picturebox is "behind" the toolstrips. I want to split the form so that the top of the form holds the 4 toolstrips and the picturebox appears below them.
What would be the proper container to put this mess into so that autosizing is the easiest? The toolstrips will most likely be "turned off and on" during the running of the app.
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Oct 22, 2009
How can I place a BG image on the tabs only (title area of tab)? I am also finding it dificult to change the tab text font, since it is changing the tab body font not the tab titles........??
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Feb 10, 2011
I'm working on a winform which contains several controls like textboxes, radio buttons, datagridviews... All of these controls have been added to a main group box called gbDataEntry. My problem is when the user is seeing the form, I set gbDataEntry.Enabled = False but I want to enable some controls like DataGridviews so the user can scroll them. After disabling gbDataGridview I set DataGridView1.Enabled = True but it seems that the datagridview does not respond to this line. Why?
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May 27, 2011
I know how to do it individually but not sure if it's possible to merge into one.
I have 6 containers that contain either Checkbox or RadioButtons.
Struggling sending the type of control and also wondered do i really need to call clear 6 times? Can't VB search each container for a control that can be checked?
vb
#Region "Form Events"
Private Sub ClearPizzaCreation(Of t As Control)(ByVal root As Control)
For Each ctrl As Control In root.Controls
[Code]....
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Jun 20, 2010
In the toolbox, under Containers section, there are some "Layout" controls. What's the use of them ?
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Oct 24, 2011
Im trying to search the entire active directory to look for a group and then see if the current logged on user is listed, then take an action based on that result.So far i have the below code which doesnt return the users who are members of the group MyTestGroup. Could anyone assist or guide me to see how i achieve this?
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Nov 29, 2010
According to this post the code below should compile, while it is not.
class Base
protected m_x as integer
end class
[code].....
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Apr 16, 2010
I'm trying to change the data binding of a listbox when the value of a combo box changes.Here is the ComboBox change code - [code]...
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Jul 2, 2010
I'm having some headaches using Structures and functions that return Nothing in VB.NET. [Code] In the previous code, when I return Nothing as result of Foo function I'd expect that st is Nothing. But this is not what happens. Then I found in MSDN documentation: Assigning Nothing to a variable sets it to the default value for its declared type. If that type contains variable members, they are all set to their default values.
So I discovered that when I assign Nothing to a structure, all its members are set to their default values, instead of the structure itself.
Also, I tried to make st a Nullable type by declaring: Dim st As Nullable(Of Test) = Foo()
but, still I can't check if st is Nothing by using: If st Is Nothing Then
or If st.Equals(Nothing) Then
So, questions:
1 - Is it possible to assign Nothing to the structure and not to its members?
2 - How can I check if a return structure value is Nothing?
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Jan 23, 2011
According to a mspress book (MCTS for Exam 70-536 .NET 2.0): You might have version compatibility issues if you ever attempt to deserialize an object that has been serialized by an earlier version of your application. Specifically, if you add a member to a custom class and attempt to deserialize an object that lacks that member, the runtime will throw an exception. In other words, if you add a member to a class in version 3.1 of your application, it will not be able to deserialize an object created by version 3.0 of your application.
Now... As curious as I am I went and created a project, serialized a class, added a new member and attempted to deserialize the class to the new object. To my surprise it worked and the newly created member was set to null by default (even if it had another default value).
[Code]...
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Oct 25, 2010
I wrote some code to add the Name and Value to Combobox.
dt = New DataTable
dt.Columns.Add("Name")
dt.Columns.Add("Value")
[Code]....
Now i want to enumerate all the ValueMemer (11,22,33,44) and all the DisplayMember (AA,BB,CC,DD) from Combobox1, how to do?
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Nov 23, 2010
i have to develop API in .Net 4.0 which can be used in VB 6.0,i know how to use this and currently i am using my this API in VB successfully.but Stuck at one place,i have collection class and i have to expose it to VB with having functionality of List class of .Net.[code]i know that generic is not supported in VB, but i think with this declaration in VB 6.0 it creates interface class for class B as IList.but in VB using object creation of class B it doesn't provides me members of LIST in intellesense like (Add,Remove of List Class)
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Jun 7, 2011
How to list Enum's members in code? I have following Enum:
Public Enum TestEnum As int32
First = 0
Second = 2
Third = 4
Fourth = 6
End Enum
And I try to list all members of TestEnum via following code but it failed:
Public Class Form1
Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
[Code].....
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Jun 22, 2010
Why does intellesense show shared members? e.g:Dim x as doublex.epsi 'Epsilon will show up as a valid member in intellesenseIs there a way to change this behavior?
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Apr 21, 2010
When I pass an an object 'MyObject' which implements 'IMyInterface' to a method parameter declared as IMyInterface, I understand that this method parameter 'sees MyObject through the eyes of its interface'.
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Jun 4, 2011
I have an EggSac object which contains references to >100 000 Egg objects. Some variables in the Eggs have to be maintained to be consistent with EggSac, so I want to make these only changeable by EggSac. However EggSac passes references to its Eggs all over the application, so if I use public methods then any other code could modify the secure parts of the Eggs by accident.
What's a proper OO way to make sure only the EggSac object can call the "secure" methods of the Eggs, but still make the "safe" methods available to everyone?
My idea is to split Egg's class into a base class containing only safe methods and a derived class containing the secure methods that only EggSac should have access to. Then EggSac has members of the type of the derived class, but it casts them to their base class whenever something else wants one.
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Sep 25, 2009
I have a form where i can add or remove AD groups from a user. But it works not 100%. Some groups I can't remove from a user. [code]..
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Jun 21, 2012
For my ToDo list I have these data: Activity, date, start time, end time.I have 2 listboxes. The first listbox stores the activity and date.The 2nd listbox stores activity,date, start time and end time.With a button I can hide/show the 2nd listbox.
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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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Sep 22, 2009
why i am getting an "reference to a non-shared member requires an object reference" error on format.Yesterday gets the previous days date and presents it in a yyyyMMdd format.vsettlementDates takes the "Yesterday value and requests data from it.
Dim Yesterday As String = format(Today.AddDays(-1), "yyyyMMdd")
Dim vSettlementDates As String = (Yesterday)
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