Copying Reference Types And String
Mar 2, 2010
I understand that an array variable contains a reference to an array object - it is a reference type. string variable is also a reference type. So, if I make a copy of either one, a change to the copy should also change the result I get when I look at the original because both refer to the same object. In the following code, I expected to see "Whoooy" as the result for original and copy for both the array and the string. It works with the array but not the string.
[Code]...
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Nov 6, 2011
I understand that an array variable contains a reference to an array object - it is a reference type. A string variable is also a reference type.So, if I make a copy of either one, a change to the copy should also change the result I get when I look at the original because both refer to the same object.
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Nov 1, 2009
I have a class with a Property called 'Value' which is of type Object.Value can be of any type, a structure, a class, an array, IList etc.My problem is with the setter and determining whether the value has changed or not.This is simple enough for value types, but reference types and lists present a problem.For a class, would you assume that the Equals method has been implemented correctly, or just assume that the value has changed every time the setter is called?If I did assume it's changed, then perhaps I should assume it for value types as well, so that the behaviour is consistent.
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Jan 11, 2012
The difference between reference types and value types is often confusing for beginners due to not understanding what a variable of value type actually holds. We know that:Value types store the actual valueReference types only store the reference to the object
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Aug 17, 2009
I'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?
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May 30, 2012
I'm integrating one of our apps with a third-party provider's web service. I've added the service reference, but when I go to dimension a var as one of their types, the types aren't showing up for me in Intellisense. I'm using VB.NET/VS 2008 on Windows 7 and a 2.0 Framework web site running on local IIS. I have imported System.Web and System.Web.Service in my codebehind. I also made sure to check the "Always generate message contracts" checkbox.Types not showing up for service reference
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Oct 29, 2011
Reading a book, the following examples are given regarding value and reference types. This example is noted as a value example. ptY display {x = 10, y = 20}
Dim ptX As New System.Drawing.Point(10, 20)
Dim ptY As New System.Drawing.Point
ptY = ptX
ptX.X = 200
Console.WriteLine(ptY.ToString())
This example is noted as a reference example. objY displays "Hello Test".
Dim objX As New System.Text.StringBuilder("Hello World")
Dim objY As System.Text.StringBuilder
objY = objX
objX.Replace("World", "Test")
Console.WriteLine(objY.ToString())
The idea is simple enough, but I just can not tell the difference between the two. Could someone explain how the heap, the stack and the New keyword play a role in accessing directly and indirectly objects and variables?
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Jun 10, 2009
Is it okay for a structure variable to hold a small number of reference types? I thinks it's fine because the pointers themselves are not that big, regardless of what they're pointing to. But I never did fully figure out the whole heap/stack thing, so I'd like to make sure.
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Mar 4, 2012
First post here so Im sorry if im posting in the wrong place. Im trying to build a simple poker game which requires the program to recognise hands of each players. Luckily there are 3rd party solutions such as pokereval. However my problem comes when i try to convert a C# ported version of pokereval by Keith Rule, into vb.net. The following error shows up referring to the line with the *.
[Code]...
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Apr 2, 2009
Im working on this webbrowser and i have fully integrated a working Proxy (it will use a proxy such as 100.00.00:0000)It will only change the proxy ip if you do the code:RefreshIESettings("100.00.00:0000")(That is a code i made, declared i mean)Anyway so heres what i wanna do:I want to have a richtextbox or something, with lines of proxy ips, such as this:
100.00.01:0000
100.00.02:0002
100.00.03:0003
[code]....
So i thought maybe if you convert that richtextbox text into a string, it might be easier?
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Jan 29, 2009
This is what I have for code:
Private Sub restoreDatabase(ByVal dbName As String)
Dim newDbName As String
newDbName = dbName.Substring(dbName.LastIndexOf("_") + 1)
My.Forms.portfolioGenerator.Close()
[Code] .....
It seems like it should be pretty simple, I take in a file name as a parameter, create a new name for it, delete it, then try to copy it back from an older version of the same file, and update the connection string. However, it continually tells me that "The file 'filenamehere' already exists." If I set overwrite to true then it goes through just fine, except it doesn't actually copy the file. Obviously I also check the folder, and the file does in fact Not exist...I've also checked all the file paths and what-not, they are all accurate.
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Apr 22, 2009
I have a copying error with my program. I am trying to copy the internet cache folder, and the error states that some files cannont be copied (read only maybe?) How can i make it copy, or just skip the uncopyable files?
My.Computer.FileSystem.CopyDirectory(Environment.GetFolderPath(Environment.SpecialFolder.Internet Cache), "d:My Documents")
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Jan 9, 2011
I'm trying to make a program that can export my schedule into a CSV file to upload on to google calender.I need to extract some text within a textbox control. I'll show you an example.This is the text in the textbox:
Quote:
Monday, 10 January, 2011
09:45 - 18:00
Phone Work09:45 - 12:15
[code]....
I need to get just the date and times from this list, and put them in variables. so that I'll end up with:
1) A string with a value as a date, which would be "10 January, 2011" for example: strDate1 would have the value of "10 January, 2011"
2) A start time, for example: strStartTime1 would have the value of 9:45
3) An end time, for example strEndTime1 would have the value of 18:00
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Mar 2, 2011
So strings are reference types right? My understanding is a reference to the string in the heap is passed even when you pass the string ByVal to a method.
String myTestValue = "NotModified";
TestMethod(myTestValue);
System.Diagnostics.Debug.Write(myTestValue); /* myTestValue = "NotModified" WTF? *[code].....
And what is going on under the hood? I would have bet my life that the value would have changed....
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Jul 7, 2010
I'm trying to create a sql query to search within an Access table that is showing inside a datagrid.
The search criterias used in the "where" bit are retrieved from info entered by the user in 3 textboxes and 1 DateTimePicker control. The first 2 fields are String type, the 3rd field is a date type (entered by the user using the DateTimePicker) and the last field in the DB table is Integer type.[ode]...
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Apr 15, 2011
I'm trying to figure out how find an object's type when it is a subclass of another object and I only know the string value of the object's type's name.I created the follwing classes:
HTML
Public Class word
End Class
Public Class noun[code]....
The problem is, using 'GetType' to check pn against a string value, I can only see that pn is a properNoun, not that its parent classes are noun and word.Is there a way to check pn against the string value "noun" or "word" and get back a positive result, indicating that pn is indeed a noun and a word as well as a properNoun?
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Oct 20, 2009
I am working on a site that I would like to pass information from one page to another. For some reason I keep getting the above error.
//Code
Partial Class Customer
Inherits System.Web.UI.Page
[Code].....
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Feb 10, 2010
I am working on a site that I would like to pass information from one page to another. I'm new to asp.net but not other languages, I'm just trying to learn some stuff. For some reason I keep getting the above error. The code I am using looks real similar to the code in the Murach book I am looking at
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Nov 12, 2010
I am extending some of the basic data types in vb.net for a large application. This includes integer, string, short, etc. As it stands, my new data type objects have names like MYInteger and MYString. Since these are the only types I'm using for my application and they are mostly compatible with the default types, is there a way I can override the defaults with mine so when you Dim iThing as Integer you're actually using my slightly customized integer type?
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Jun 22, 2010
I have a problem with Operator '&' someone may with this problem.
[Code]...
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Jan 14, 2010
I am trying to concate string and system.type using operator & in VB and i am getting error :
[Code]...
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Jun 8, 2010
This should be an easy one, looks like I got myself too confused.I get a table from a database, data ranges from varchar to int to Null values. Cheap and dirty way of converting this into a tab-delimited file that I already have is this (shrunken to preserve space, ugliness is kept on par with original):
da.Fill(dt)
' da - DataAdapter '
' dt - DataTable '
[code].....
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Jun 5, 2009
I'm not sure if i titled this question properly or am asking it properly, but here goes.I've got serialized objects (in XML) stored in a database, along with a string/varchar indicating the type.
[Code]...
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Mar 24, 2011
I have an Array of Column Titles and Column tpyes that i want to add to my DataGridView but dont
know how to 'Cast the string' to the required Column type?
Example (doesnt work but might give you an idea what i an after:[code...]
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Nov 25, 2011
Adding different types of Colums to a DataGridView when the type starts as a string
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Feb 15, 2012
i try to put picture in mysql with vb.net, first i convert with this function : [code] i try to use that function for storing picture to mysql database : INSERT INTO myImage (image) VALUES ('" & convertImage(PictureBox1.image) & "');and then i have this error : Operator '&' is not defined for types 'String' and '1-dimensional array of Byte'i create a table (myImage) with image field (LongBlob)
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May 17, 2012
i am downloading data from xml using linq library those data i want to add them on a textblock item
TextBlock1.Text = TextBlock1.Text & result
but it has an error :
Error 1 Operator '&' is not defined for types 'String' and 'System.Xml.Linq.XElement'.
When i am changing this line to :
TextBlock1.Text = TextBlock1.Text & result.Tostring
it works but it adds this data :
"<"data> data <"/data>
instead of :
hello
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Apr 26, 2010
I am having a problem in the following codes
Problem in "'" & rawData & "'")"
Error Message Operator '&' is not defined for types 'String' and '1-dimensional array of Byte'.
Complete Coding:
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim fileSize As Integer
Dim rawData() As Byte
[code]....
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Sep 2, 2009
with this code dont know wht its not working source = wc.DownloadString(String.Format("http://" & cboHSearch & "/cse?cx=013269018370076798483:gg7jrrhpsy4&cof=FORID:1&q=" + cboEngine.Text + "&sa=Search", Me.cboEngine.Text.Replace(" "c, "+"c), resultCounter))
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Apr 11, 2007
To simplify my problem, lets say I have 200 textboxes on a form. I want the first 100 to become disabled in a certain subroutine. I don't want to write 100 lines to disable each textbox; I'd rather write a loop to do it but can't figure out how. For instance:
dim i as integer
dim s as string
for i = 1 to 100
[Code].....
I tried "dim c as new control" then "c.name=s" but I don't think this makes "c" as a member of my form and it didn't do anything as a result. I think I need to figure out how to declare c as a control that exists within my form but can't figure out the syntax for that.
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