Why Is List.add() Adding Items To Object AND Source Object As Well
Jun 15, 2011
I need to be able to add elements to a copy of mylist.testlist without modifying the global mylist object. (Which seems to be happening via the below code.)When I am working on x, which should be a totally separate object, mylist is getting modified as well. How can I fix this? I have worked with lists extensively and never seen this behavior before. I have tested and reproduced the problem in .NET 3.5 and .NET 4.0 on Win 7 Pro 32bit.
Source Code:
Public Class Form1
Public mylist As New test
Sub Main()
[code]....
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Mar 28, 2010
I have some code that adds items to a List(of Object).
Here's my original code
Dim BeaconStoryList as New List(Of My.StoryType)
Dim BeaconStory as New My.StoryType
Dim NewStories() as New Foriegn.StoryType = GetStories
[Code]....
But as soon as the code assigned "Chicken" to BeaconStory.Title, then BeaconStoryList(0).Title would also change to "Chicken".
With my second version of the code this did not happen.
It's as though it was placing pointers into the elements of the array rather than values. If that is the case, however, then why does my second version of the code work - I'm still passing in the same thing - aren't I?
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Apr 25, 2011
I have a class that has a property that I declare like this:
VB.NET
Private _DirectoryList As List(Of FileDirectoryInfo) ''' <summary> ''' Array of directories. ''' </summary> ''' <value>Object</value> ''' <returns>Directory array list</returns> ''' <remarks>N/A</remarks> Public Property Directory As List(Of FileDirectoryInfo) Get Return _DirectoryList End Get Set(ByVal value As List(Of FileDirectoryInfo)) _DirectoryList = value End Set End Property
[Code]...
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May 24, 2011
I am trying to find way to design a report using my own custom class. I found links:
1.) How to work in Crystal Report with Object Data Source?
2.) Use .net object as data source in Crystal Report 2008
3.) Binding object with List<> to Crystal Report
4.) How to assign Custom class as datasource in crystal report
They were quite helpful, but I have been stuck in the first step while designing report as my custom class's property is not listed in field list of crystal report design view.[code]When I add my class objects to crystal report I do not get the usertype field from users class in field list.So how can I add usertype field to my field list? Or do I have to take another approach?The reason i wanted to use it as i am:
1.) Showing a form where user can type keyword
2.) program filters the records as per keyword using LINQ
3.) when user clicks the print button, I want to set the filtered records as datasource of my report
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Aug 5, 2011
I am not sure what I'm doing wrong, but I need some guidance from people smarter than me...
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Sep 3, 2009
After reading all the examples for list of T exists and Find and find first, none show how to handle multi-property objects. Below is bare bones example maybe someone could flesh out to show how this should be done.
Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim DatePriceList As New List(Of DateAndPrice)
DatePriceList.Add(New DateAndPrice(Date.Parse("1/1/2000"), 10.12))
DatePriceList.Add(New DateAndPrice(Date.Parse("1/2/2000"), 11.12))
[Code]...
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Nov 6, 2011
I have created a list of another class and loaded the list with data. using breakpoints I can see that the data is loading and visible in my form page. However, when I attempt to access the list using a For Each loop, I get an error saying that "Value of type Customer can not be converted to Integer"I am trying to follow examples from tutorials on accessing list elements, but they are never lists of objects, so I am not sure what I am doing wrong.
My class that I have made a list of:
Public Class Customer
Private m_firstName As String
[code]......
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Aug 12, 2010
Good example using the List(T) object. I need to be able to add and remove items from it.
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Jun 20, 2012
I'm trying to add objects from a class I created using data from an excel worksheet to a list using a for loop [code]When I run it I receive "System.NullReferenceException was unhandled by user code Message=Object reference not set to an instance of an object."
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Jan 4, 2012
trying to write an updateview method to basically clear the contents of the current listbox and then loop through a list of objects and pass 2 items from each of the objects in the list into the listbox.This is what I have so far
vb.net
Public Sub updateview()
holidaylistbox.items.clear()
[code].....
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Sep 6, 2011
Limited to using v2.0 of .Net framework (we use VB.net) due to environmental constraints on our servers.I've got an ASP.net webpage which pulls data from a webservice that performs checks on user accounts in active directory. Operators can check multiple accounts at one time using the web interface. The webservice returns a list(of AccountCheck) objects which themselves contain single properties like username, email address, and List(of AccountError) objects which contain multiple properties.[code]What I want to do is using some kind of repeater, create multiple panels or divs which contain labels showing the username, email etc, and a gridview which has the accounterror list bound to it to show all the errors. The users could be checking 2, 5, 7 accounts at once, and is dynamic.
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Jul 15, 2010
I have a problem with a generic list, which consists of intances of a class i created. I am just amazed, each time I add a new object to the list, it overwrites the previous entries. Here is a code sample, i just can't beleive it. I am using visual studio 2010:
Dim translations As List(Of TranslatedValue) = New List(Of TranslatedValue)
If Session("ctlTexts") Is Nothing Then
Dim reader As IDataReader = DataAccessFunctions.db.GetDataReader("SELECT [ControlID], [ControlTextEN], [ControlTextDE], [ControlTextBG] FROM [dbo].[tbLanguage]", GetConnectionString)
[code]....
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May 19, 2009
I am working in VB.net and have a Class, Foo, that implements an interface, IBar.I have a List of Foo's, but I need to pass a list of IBar's into a function, but I keep getting casting errors, even when I use DirectCast.My code is [code]MainWorks works, but it would be really annoying and inefficient to have to do that everywhere I want to call this function.
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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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Nov 8, 2010
How to know if a List(Of T) contains any control object without using a loop ?This doesn't work
Dim lstObject As New List(Of Object)
lstObject.Add("STRING")
lstObject.Add(2)
[code].....
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Jul 29, 2010
I would like to ask what is the efficiency way the clean and dispose the object collected in the List (Of Object)?
Is that by calling the List.Clear() method will automatic clean all the object collected by it?
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Feb 11, 2011
I am able to populate an object and output everything. How do I remove say the name2 object?
la.Remove(Logins("name2")) doesn't seem to work.
Private Sub btnListArray_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnListArray.Click
[code]....
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May 29, 2012
Suppose I have a list of Cat.
Public Class Cat
Public Property id As Guid
Public Property name As String
Public Property race As catRace
End Class
How can I quickly transform this List(Of Cat) into a List(Of Guid) using the id property?
I could do :
Dim newList As List(Of Guid)
For each item in catList
newList.Add(item.id)
Next
But I think there must be a way to do this faster (1 LOC). I just can't find how.
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Nov 1, 2011
MVC 3 razor VB.NET project. I have resorted to manual building a list for a drop down box so I can insure certain values are available in the select list and also to control what the first item is in the list. The below is my code snippet for the part that is giving me problems..
[Code]...
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Jun 21, 2010
I am trying to create an list or an array of a class.Here is my "Ingredient" class that I am trying to create a list of:[code]In my "recipe" class, I am want to create a list (or array) and I am drawing a big blank on how to do it. Can anyone point me in the right direction?
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Jul 10, 2010
I am somewhat new to object oriented programming and am attempting to flatten a Linq object hierarchy by using a shim class.how to initalize a derived class with property values from a base class?I have two objects, a base object with about 100 properties, and a derived object which inherits from the base object and adds a few additional properties beyond those of the base object. My simple constructor creates the derived object, but I am looking for a way to initialize the derived object properties with values from the base object.Right now I am using reflection to iterate over the properties individually and I suspect there may be a better way. The following example shows my shim class constructor for the derived class, and two properties:
newProperty1 - a new string property of the derived class
flattenedProperty2 - a new string property of the derived class, copied from a 2nd-level object of the base class
Code example:
Public Class derivedObj
Inherits baseObj
Private _newProperty1 As String[code].......
Is this the correct constructor approach to flatten the object hierarchy using a shim class? My second question relates to initialization of properties in the derived class. The constructor above creates the derived object, but what is the best way to initialize the derived object properties with values from the base object? The following code uses reflection to iterate over the properties individually, but I suspect there may be a better way.
Code example:
' property names are in the string array fieldNames
'baseObjQuery is an ienumerable of baseObj
'derivedObjList is a list of derivedObj[code].....
Is there a simple way to initialize values for the properties in the derived object based upon the values of the common properties in the base object?
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Jun 15, 2012
I am having a problem when setting VB.NET list object to another.I create an instance on ReadLocations and than create an object of ReadLocation where then I loop through ReadLocations and set ReadLocation1 equal to rl. What happens is that if I then go and change ReadLocation1 to something else (assdfhsd) it will also change the ReadLocations index. I am really confused why it would be doing that unless it is "=" sign means referencing instead of actually setting the value. Please help as I am a C# developer but the program I am modifying is in VB.NET.[code]
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Dec 19, 2011
I've created A list of object "emails" which contains the "email" object which has 3 parameters (String Address, String Subject, String Body)I then want to add to the list by creating more instances of "email". However, I've tried so many different ways and it's having none of it.
Public Class Test
Public emails As List(Of Email)
[code].....
If I click button1 I get the error "Object reference not set to an instance of an object".
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Jul 20, 2011
I am attempting to read the results from a SQL query into a List(Of) and I can see the List.count while adding items to the List increments, however in another part of my code when I am attempting to read the List the List.Count returns 0. My List is as follows:
[Code]...
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May 9, 2011
I'm creating a gridview using an objectdatasource and it works fine when pulling all records. But when I want to use the selectCountMethod the grid shows no values. I Step through the code and my getInvoices (gets the requested data) returns data and the getInvoicesCount (gets the total record count). But then when I go through the rowdatabound of the gridview there's nothing in there and no data displays. Here is my code to set the objectdatasource. Any reasons why it wouldn't work or something special that needs to be done for getting the selectcount to work? [code]
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Jun 5, 2011
i'm getting error of data source object is invalid when i try to load a transaction report from sql database.
[Code]...
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Sep 18, 2010
I am using LinqPad to learn Linq by querying the NetFlix OData source.Here is the query I got working which is awesome.[code].....
(Pardon all the comments...it is a testament to the fact I am experimenting and that I will change the query for various needs).There are two thing I cannot figure out.First.Let's say I only want to return the first 10 results.Second (and most importantly). I want to filter by a partial string of the genre.Each title contains a Genres collection. I want to show only Genres where the Name contains a certain string (like "Family").Even better filter using Titles where genre.name.contains "firstFilter" AND "secondFilter".Basically, I want to filter by genre(s) and I cannot figure out how to do it since Title contains its own Genres collection and I cannot figure out how to return only title that are in one or more genres of the collection.
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Mar 26, 2009
In VS2005, how could you get the current web page's source in VB.net's webbrowser object? I need to load a webpage up, and then grab everything out of the header and body tags, and then I want to replace some text inside of those tags, and then reshow the page with the updated source.
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Oct 16, 2009
Does link text mean I have to return a concrete implementation? Even though I am using svcutil with the /r that includes my entites(where IMyInterface is defined). I get no errors but it changes all List(of IMyInterface) to list(of Object) and I cannot deserialize it on the client
Error: list(of object) cannot be converted to list(of IMyInterface).
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Apr 15, 2011
i created more projects using ReportViewer 2005 and 2008 in local processing mode than I can count on my hands. All Visual Studio 2005 or 2008 ASP.NET web forms projects. I always used some flavor of Object data source for the reports.Tonight, I attempted to add the same functionality to a Visual Studio 2010 MVC 2 project and am failing miserably. First, the Add New Item > Reporting > Report is now a 2008 RDLC and not a 2005 RDLC report. Secondly, when trying to add a DataSet, my usual method of create a data proxy class with static methods that return IEnumerables(Of Stuff) will not show up as sources in the DataSources drop down
Thirdly, my only option is to add a Database connection. There is no "Object Data Source" to pick from: Like I kind of alluded to, I have no problems whatsoever actually rendering a report using the ReportViewer control. What I can't do is figure out how set up a Data Source in these new-fangled 2008 reports with Visual Studio 2010 so that I can pump a list of domain objects into the ReportViewer and display the report.
UPDATE: With some more research, I've found that MVC projects do not allow object data sources to be used within them. One solution for my issue is to create a separate project in the solution -- a web application, a service, or even just a class library, to add the report to and design it accordingly.'m still looking for alternatives here, so don't run away too fast!
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