Say I have a generic list that is a list of a structure.
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I always get an error that it's a value and cannot be set. Is there a way to change it without having to make a local copy of the item, then set the item on the list to that local item?
If I increase the capacity of a given list, or add elements until count>capacity, does this mean the program is actually copying the entire list's contents to a new space in memory (similar to redim preserve with arrays)? If so, than I have really been hurting the performance of my lists, as before I was inserting and adding without a second thought. This seems a strong restriction on the dynamic abilities of lists.
View 2 RepliesI have a basic bubble sorting algorithm that can sort either A-Z or in numerical order with just the change of a "less than" or "more than". However, I have to use the code twice in order for it to sort correctly.
'Sub Sort(ByVal array As Object)
'--A-Z
If Array(i) > Array(i +1) Then
[code]....
Anyway, if there is a way to do it, that'll allow me to have just one sort instead of having two sorts which use the same sorting algorithm, but just a different comparator.
In VB.NET 2010, how to return a boolean value as generic type without compile warning?
View 2 RepliesI am creating a 'generic input dialog': InputDialog(Of T).The idea is that I can create new instances of this dialog for different values of T. For example,I can create an InputDialog(Of String) and it displays a textbox.I create an InputDialog(Of Boolean) and it displays two radiobuttons (I could use a Checkbox, irrelevant).I create an InputDialog(Of Date) and it shows a DateTimePicker.
I do this by simply checking the type of T at run-time.In this way it is not really generic, as the dialog still has to know which type T is (which is usually not the case), but the generic is in the fact that the T can be multiple types that require a TextBox. For example, InputDialog(Of String), (Of Integer), (Of Single), (Of Double), etc, all simply display a TextBox (and it is validated later),so I still want to use generics as much as possible.Anyway, the result of the dialog is of course a property of type T. This property needs to return the value in the textbox, converted from string to T, OR the value in the DateTimePicker, converted from Date to T,OR the checked property of the 'Yes' radiobutton, converted from Boolean to T.In order to convert from any object to T I googled and found this
vb.net
Imports System.ComponentModel Public Class GenericTypeConverter Public Shared Function FromObject(Of T)(ByVal value As Object) As T Dim tc As TypeConverter = TypeDescriptor.GetConverter(GetType(T)) Return CType(tc.ConvertFrom(value), T) End Function End Class
I have to use this, I cannot simply CType a string to T since a String cannot be converted to any type T.So, my Result property looks like this at the moment:
vb.net
Public ReadOnly Property Result()[code].....
This actually works for Strings, Integers, Doubles, Singles, etc. I pass it the String in the textbox and it converts it to 'T'(note: T is then a String, Integer or Double!) just fine.So, it can convert a String to a String, Integer or Double without any problems (I am validating the text before using the Result property so it will always be a valid integer, double, etc).However, it does not work for a Boolean, nor for a DateTime. When I try that, it says "BooleanConverter cannot convert from System.Boolean" or "DateTimeConverter cannot convert from DateTime". I realize it is a bit of a strange thing, since the object already IS a Boolean or a Date(Time) so no conversion should be done at all, but this doesn't work in design-time because I need to return the objects as type T.I know that T will be Boolean when the value to be converted is a Boolean, and that T will be DateTime when the value to be converted is a DateTime, but the designer does not accept a simple CType. As I said, it does not accept this:
Return CType(rbYes.Checked, T)
because 'Boolean cannot be converted to T'.
However, I did find a way to make it work, but it seems like a complete hack... I can assign the boolean to an Object and then convert that using CType:
Dim obj As Object
obj = rbYes.Checked
Return CType(obj, T)
This works, it's accepted during design-time, and it works during run-time, but it seems very wrong... Is there no better way to handle this?
From what I read it is a good convention to name a method that returns a boolean value with the prefix of "is" or "has". So in keeping with this convention I am trying to name a method in my program with this prefix but I am running Specifically I have a class called Day. It is a simple class with a few data members and one method that returns a boolean value of true or false. The name of the boolean variable is isSpecialDay. This class has a method called isSpecialDay which takes the date of the day, applies some criteria to the date and then sets the variable isSpecialDay to true or false. My problem is that the boolean variable is named isSpecialDay and so it the method. What should I do?
Public Class Day
Private TheDate as String
Private DayName as String
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I am trying to create a list of a generic type in vb.net 2.0 framework.
This is the generic type definition:
Public Class GenericParamMap(Of T)
Public Sub New(ByVal pParamName As String, ByVal pPropValue As T)
mParamName = pParamName
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The compiler does not allow a "T" in the method's parameter because it's not defined, but I'm not sure how or where to define it. I thought it was okay to have a generic method definition.
how to find a value in the System.Collections.Generic.List.I have:
Private ids As New List(Of Byte())
ids.add(New Byte(){&HA8,&H0F})
ids.add(New Byte(){&HFF,&H03})
ids.add(New Byte(){&H10,&H00})
I would like to find for example: &H10,&H00 in that list and if there isn't the stuff I wan't to find then how do I know that?
so I have a generic list in a console application. Dim Channels as New List(Of Chatroom) Chatroom is a structure. But I have multiple classes, threads, and timers looping through this list, sometimes at the same time, but it always seems to raise errors because the number of items in the list gets changed while one of the other classes/threads/timers are looping through also. Is there any way to allow only one to manipulate it at a time?
View 8 RepliesI'm looping all the properties in an object via reflection:
For Each p As PropertyInfo In values.[GetType]().GetProperties()
If p.CanRead Then
'Do stuff
End If
Next
how to determine whether the property in question is a generic List(Of T)? If it is I need to loop the list itself.
I've experimented with GetType and TypeOf but have not managed to get anything working.
To clarify, I want to keep this generic. I do not want to specify the type of T, I need to loop the list items and call the ToString method on each item. T could be one of a number of different types (application specific reference types). Is it possible to do this without specifying types?
(VB.NET 2005 with .Net 2.0)
Public Class notifierMain
Public Class Contacts
Inherits List(Of row)
Public Sub New()
[code]....
When I debug this winforms application I get curType = "notifier.notifierMain+Contacts+row" I want to the Validate function to know it is in MyContacts. How do I do this?
I've got a listbox named, Listbox1 I need to set it so the selectedindex, is equal to the mediaplayer song on playlist. here's my
Change Index:
Private Sub ListBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ListBox1.SelectedIndexChanged
Dim x As Integer
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i have issue returning a list in a web method. here is the code
<WebMethod()> _
Public Function getTags(para_parents As String) As List(Of getTypeDetailsByParentName_Result)()
Dim context As New PPEntities
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the error is
Value of type 'System.Collections.Generic.List(Of SaftyonRoad.getTypeDetailsByParentName_Result)' cannot be converted to '1-dimensional array of System.Collections.Generic.List(Of SaftyonRoad.getTypeDetailsByParentName_Result)'
it seems always at this time I cant figure out how to do something maybe it has something to do with lunchtime.
Im having trouble using a method that is defined by an outside company
This is a link to their integration guide:
[URL]
This is their documentation for the class Im trying to use
OrderQueryWebService Class
This class is for SID in particular and is made for use with the notification methods. This is for the Order Query Web Service specifically, allowing clients to return the status of transactions for their merchant, whenever they want to.
Methods
/ <summary>
/ Pass through the variables required and receive a list of Transaction
objects showing transaction status
[Code].....
The MerchantCode, the MerchantUsername, the MerchantPassword are all good the List is a custom type called SetComHash.Transaction
Everytime I try adding a string to the list such as the transactionNumber and some other values it gives me a type error:
"Value of type string cannot be converted to 'SetcomHash.Transaction'
PROJECT TYPE: Windows Forms Application
LANGUAGE: Visual Basic
.NET VERSION: 3.5
IDE: Visual Studio 2008
OPTION STRICT: on
OPTION EXPLICIT: ON
I need to populated a ComboBox and a CheckedListBox with a list of the Windows Accounts on the host computer. I also need to the user to be able to apply settings to the users individually. Thirdly, I need to find a way to add a startup registry key in the CURRENT_USER for a different user than the "Current User" (For example: User1 is an Administrator. User2 is a Limited Account [can't modify registry]. User1 needs to add Registry key to User2's "CURRENT_USER". This is a parental control application so the Admin accounts need to be able to access the registry from all users without affecting all users at once. I do not have any code to paste because I still have not the foggiest idea of where to start. I think it probably has something to do with an array (I have no experience with arrays whatsoever) but I am stumped from there. I'm a new, self-taught programmer so I speak idiot at times,
Summary of Questions
1) How do I retrieve a list of Windows Users?
2) How do I populate the objects above with such a list?
3) How do I interact with the items on that list (specific user accounts)?
4) How do I modify another user's CURRENT_USER Registry key?
What would be the fastest way to sort a list that contains a list of objects, based upon another list? An example follows:Say I have multiple lists of employees. Each individual list has a common property value, say "Department". So I have a list of employees, in one list they all have the department string value of "Sales". In another list all the objects have a department value of "Finance". These lists of employees are then contained in a list which holds them all.
I have a second list, which should drives the sort order of the employee lists. The second list simply contains a list of strings like, "Finance", "Sales", "IT" and so on. I'd like my lists of customers to be sorted in the order of "Finance", "Sales", etc.I'm using VB.NET in .NET 2.0
Dim x = GetType(List(Of )) 'valid statement
Dim list As New List(Of String)
Now I want to see if list is a List(Of T) variable: Dim isList = TypeOf list Is List(Of ) On the last line I get a compile error: "Type Expected". Is there any cheap-performance TypeOf operator alternative for generics?
I have converted c# .cs to vb:= I have 6 errors on:
Red "List" says Too few type arguments to system.Collections.Generic.List(Of T)'
Orange "Calendar" says Value of type 'System.Windows.Forms.Control.ControlCollection' cannot be converted to 'Form1.Kobush.Windows.Forms.Appointment'.
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If i have an object that implements an interface (and don't know the exact object) i can call a sub (DoSomething) by going:
vb
Dim iObj = trycast(something, iInterface)
if iObj isnot nothing then
iObj.DoSomething()
end if
How can I do this for a Generic? such as...
vb
Public Class TestClass(of T)
Public sub DoSomething()
....
end class
i m getting a collection of data in list's object. And from this list i want to get the maximum id.`
Dim objinfo As List(Of AlbumInfo) = objPhotos.GetPhotos_Alb_ID(Me.ModuleId, hdd_AlbID.Value)
Dim Photo_Image As String = ""
Dim str As String = Photo_Image & fu_Photo.PostedFile.FileName.Substrng(fu_Photo.PostedFile.FileName.LastIndexOf("."))
[code]....
this returns the "0"th positions id from Convert.ToString(objinfo.Item("0").Photo_Id + 1)but i want to get the last item's id.
i have list of string like this :
Dim totalPrice As New List(Of Integer)
how can i get sum of column(0) (C# or VB) ?
<div class=PhorumReadBodyText>Hi, I have a problem with adding of items to generic list, problem is when I insert 1. item to the list, everithing is ok, but if I insert second item, first and second has same values.
code looks like that (asp.net 4.0): </div> <div class=PhorumReadBodyText> </div> <div class=PhorumReadBodyText>Partial Class _Default
Inherits System.Web.UI.Page
[Code]...
I have a problem with adding items to generic list, problem is when I add 1. item to the list, everything is ok, but when I add second, first and second has the same values...
This is code (asp.net 4.0):
Partial Class _Default
Inherits System.Web.UI.Page
<Serializable()>
Public Class Product
Shared Property Material As String
[URL]
In my VB.net application I am populating my customer object and looping through it as shown below.As there are thousands of customers, I want to do it 500 customers at a time.Is there anyway I can have one more For loop to process 500 customers at one shot in vB.netI am not using LinQ as the database is Oracle.[code]
View 2 RepliesI want my loop to loop until it reaches the last string in my generic list. I know I could simply insert the last index of the list as an integer but I want to be able to use this if my list grows too. How could I achieve this?
View 5 RepliesI have been reading extensively about searching generic lists in VB.NET with the usage of delegates.However, I still cannot seem to grasp how to achieve what I want to, which I believe is frustratingly simple! I have a list populated with instances of an object with three parameters (fields/ variables).When I receive a new object to add to the list I want to search the list for the "layer" field.If the field matches then I will replace that row (object) in the list with the new object, if no match is found then I will add it to the list. [code]
View 3 Repliesi have a generic list of type datarow.i have to split this list at an index and then use both parts of the list.
View 2 RepliesI'm using VB.NET on Framework 2.0. I'm looking to quickly group a Generic List<> by two properties. For the sake of this example lets say I have a List of an Order type with properties of CustomerId, ProductId, and ProductCount. How would I get the average of ProductCounts grouped by CustomerId and ProductId in VB.NET ?Unfortunatly I cannot do this at DB level (which would have been easy). Also I cannot use LINQ or Lambada as Im on Framewwork 2.0. So I need to do this at application level in VB.net. The list is returned to me sorted by CustomerId and ProductId so I guess with a few loop sI should be able to create a average value for but there must be a cleaner way to do this?
View 1 RepliesI have the follow code in my program where I hit a SQLCe database to append the results into a list. That part works, but instead of exiting the function 'QueryDB' it goes to the else statement and runs the function again, which will return a null value. I designed it this way becuase I wanted to check to make sure the database is open before I try to execute the SQL statement, and if it's not open, call the method to open it and run through the function again.
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We have a generic List(Of Product) that must be sorted on two or more properties of the Product class.
The product class has the properties "Popular" numeric (asc), "Clicked" numeric (desc), "Name" string (asc). In order of naming the properties we want the list to sort.
How can it be sort with an lamba statement? If have found to sort the list based on one property.