I am looking to compare values of 2 different ArrayLists, and remove any duplicates from 1 ArrayList.
Example:
Arr1 = {HF,HA,GM,RV}
Arr2 = {FB,HA}
Since they have 'HA' in common, I would like to remove 'HA' from Arr1. Any help or point in the right direction would be appreciated.
You can use LINQ's Except but you will have to convert array lists to regular arrays first:
https://msdn.microsoft.com/en-us/library/bb300779(v=vs.110).aspx
Dim list1 As New ArrayList()
list1.Add("A")
list1.Add("B")
list1.Add("C")
Dim list2 As New ArrayList()
list2.Add("A")
list2.Add("B")
Dim array1 = list1.ToArray()
Dim array2 = list2.ToArray()
Dim except = array1.Except(array2).ToArray()
Also if you need a custom comparison, use this overload instead:
https://msdn.microsoft.com/en-us/library/bb336390(v=vs.110).aspx
EDIT
There are very few LINQ methods available for ArrayList, however you can convert it back very easily:
Dim arrayList as New ArrayList(except)
Related
is there any way to remove the element in char array I converted from a String?
Dim myString As String = "Hello"
Dim charArray As Char() = myString.ToCharArray
Your help would be much appreciated.. Thanks
Arrays are fixed-length in .NET. You can set an element to Nothing but you cannot remove that element. You can use a collection instead of an array and then you can add, insert and remove items at will, but your example isn't necessarily the best case for that sort of thing, e.g.
Dim str = "Hello"
Dim chars = New List(Of Char)(str)
You can then call Remove or RemoveAt on that List to remove a Char. You can then create a new String if desired, e.g.
chars.RemoveAt(2)
str = New String(chars.ToArray())
Console.WriteLine(str)
That will display "Helo".
Dim myRandom As New Random
Dim myList As New List(Of String)(New String() {"A", "B", "C"})
myList.OrderBy(Function(i) myRandom.Next).ToList()
For k As Integer = 0 To 2
MessageBox.Show(myList.Item(k))
Next
When you run the code, you will see that the MessageBoxes show A,B,C.
I want MessageBoxes show B,C,A or C,B,A or A,C,B or A,B,C or B,A,C or C,A,B according to randomized result.
Note: Using Linq is a must.
The issue is that your code doesn't make any changes to myList. A LINQ query ALWAYS generates a new list. You need to assign the result of ToList back to your myList variable, i.e.
myList = myList.OrderBy(Function(i) myRandom.Next).ToList()
Needed code is something like this:
Dim myArray(0) As String
Dim ay As String = "ay"
myArr & ay(0) = "asd"
I've tried but did not worked
Dim classlist1(0) As String
Dim classlist2(0) As String
Dim classlist3(0) As String
Dim classlist4(0) As String
Dim count As Integer = 0
For _year As Integer = 1 To 4
("classlist" & _year)(count) = "hi"
count += 1
Next
Any time you see something like this:
Dim classlist1(0) As String
Dim classlist2(0) As String
Dim classlist3(0) As String
' etc.
It's an indication that you're using the wrong data structure. Instead of trying to dynamically build variable names (which isn't really possible in a static language, at least not without some really ugly reflection code with a high potential for runtime errors), just use a collection.
For example, if you want a collection of strings:
Dim classList As New List(Of String)()
And if you want a collection of collections of strings:
Dim classLists As New List(Of List(Of String))()
Then you can reference the nested lists within the parent list. So to add your first "year" of classes:
classLists.Add(new List(Of String))
And add a class to that year:
classLists(0).Add("some value")
As you can see, it starts to get a little difficult to keep track of the data structures. This is where creating custom types and structures becomes very useful. For example, rather than representing a "year" as a list of strings, create an actual Year class. That class can internally hold a list of strings, and other logic/data.
Try Dictionary<TKey, TValue> Class From MSDN.
Dim classLists As New Dictionary(Of String, String)()
'Add items with keys
For _year As Integer = 1 To 4
classLists.Add(String.Format("classlist{0}",_year), "hi")
Next
And you can get value by key later
Dim key As String = "classlist2"
Dim value As String = classLists(key)
whats the easiest way to convert an array of integers into string form? I'm trying to copy the whole array of integers into strings.
{1, 2, 3}
to
{"1", "2", "3"}
The easiest method would be to use the Select extension method which is provided by LINQ:
Dim intArray() As Integer = {1, 2, 3}
Dim strArray() As String = intArray.Select(Function(x) x.ToString()).ToArray()
If you don't want to, or cannot use LINQ, you can use the Array.ConvertAll method, which is almost as easy:
Dim strArray() As String = Array.ConvertAll(Of Integer, String)(intArray, Function(x) x.ToString())
EDIT
Based on your comments, below, it looks like you need to convert from an ArrayList of integers to an ArrayList of strings. In that case, you could do it like this:
Dim intArray As New ArrayList({1, 2, 3})
Dim strArray As New ArrayList(intArray.ToArray().Select(Function(x) x.ToString()).ToArray())
Although, at that point, it's starting to get a bit messier. It's probably easier to just do a standard loop, like this:
Dim myArray As New ArrayList({1, 2, 3})
For i As Integer = myArray.Count - 1 To 0 Step -1
myArray(i) = myArray(i).ToString()
Next
For what it's worth, though, unless you are still on a really old version of the .NET Framework, you really ought to be using the List(Of T) class rather than the ArrayList class, in most cases.
First try
Dim holdValues() As Integer 'Doesn't Work
holdValues(1) = 55
Second try
Dim holdValues(-1) As Integer 'Gives me Index was outside the bounds of the array.
holdValues(1) = 55
I'm trying to do something similar to
Dim myString(-1) As String
But apparently this doesn't apply to integer arrays. I don't know what the size of the array will be, it wont get smaller but it will grow larger.
Any help will be appreciated, thank you!
You could use the Initializers shortcut:
Dim myValues As Integer() = New Integer() {55, 56, 67}
But if you want to resize the array, etc. then definately have a look at a List(Of Integer):
'Initialise the list
Dim myValues As New System.Collections.Generic.List(Of Integer)
'Shortcut to pre-populate it with known values
myValues.AddRange(New Integer() {55, 56, 57})
'Add a new value, dynamically resizing the array
myValues.Add(32)
'It probably has a method do do what you want, but if you really need an array:
myValues.ToArray()
you add the number to
holdValues(x) //x+1 will be size of array
so something like this
Dim array(2) As Integer
array(0) = 100
array(1) = 10
array(2) = 1
you can re-allocate the array to be bigger if needed by doing this.
ReDim array(10) as Integer
you'll have to add in your code when you should make your array bigger. You can also look into lists. Lists take care of this issue automatically.
here's some info on Lists: http://www.dotnetperls.com/list-vbnet
Hope this helps.
Also a link for general knowledge on arrays http://www.dotnetperls.com/array-vbnet