How can I delete an item from an array in VB NET

Question

User · Answer

That depends on what you mean by delete  An array has a fixed size  so deleting doesn t really make sense   If you want to remove element i  one option would be to move all elements j  gt  i one position to the left  a j - 1    a j  for all j  or using Array Copy  and then resize the array using ReDim Preserve   So  unless you are forced to use an array by some external constraint  consider using a data structure more suitable for adding and removing items  List lt T   for example  also uses an array internally but takes care of all the resizing issues itself  For removing items  it uses the algorithm mentioned above  without the ReDim   which is why List lt T gt  RemoveAt is an O n  operation   There s a whole lot of different collection classes in the System Collections Generic namespace  optimized for different use cases  If removing items frequently is a requirement  there are lots of better options than an array  or even List lt T gt

User · Answer

My favorite way   Imports System Runtime CompilerServices   lt Extension   gt    Public Sub RemoveAll Of T  ByRef arr As T    matching As Predicate Of T       If Not IsNothing arr  Then         If arr Count  gt  0 Then             Dim ls As List Of T    arr ToList             ls RemoveAll matching              arr   ls ToArray         End If     End If End Sub   Then in the code  whenever I need to remove something from an array I can do it by some property in some object in that array having a certain value  like   arr RemoveAll Function c  c MasterContactID Equals customer MasterContactID     Or if I already know the exact object I want to remove  I can just do   arr RemoveAll function c  c equals customer

User · Answer

Public Sub ArrayDelAt ByRef x As Array  ByVal stack As Integer      For i   0 To x Length - 2         If i  gt   stack Then             x i    x i   1              x x Length-1    Nothing         End If     Next End Sub   try this

User · Answer

You can t  I would suggest that you put the array elements into a List  at least then you can remove items  An array can be extended  for example using ReDim but you cannot remove array elements once they have been created  You would have to rebuild the array from scratch to do that   If you can avoid it  don t use arrays here  use a List

User · Answer

Seems like this sounds more complicated than it is         Dim myArray As String     TextBox1 Lines      First we count how many null elements there are        Dim Counter As Integer   0     For x   0 To myArray Count - 1         If Len myArray x    lt  1 Then             Counter    1         End If     Next      Then we dimension an array to be the size of the last array      minus the amount of nulls found        Dim tempArr myArray Count - Counter  As String       Indexing starts at zero  so let s set the stage for that        Counter   -1      For x   0 To myArray Count - 1          Set the conditions for the new array as in          It  contains  word    has no value  length is less than 1  ect          If Len myArray x    gt  1 Then             Counter    1              So if a value is present  we move that value over to              the new array              tempArr Counter    myArray x          End If     Next   Now you can assign tempArr back to the original or what ever you need done with it as in     TextBox1 Lines   tempArr  You now have a textbox void of blank lines

User · Answer

The variable i represents the index of the element you want to delete   System Array Clear ArrayName  i  1

User · Answer

As Heinzi said  an array has a fixed size  In order to  remove an item  or  resize  it  you ll have to create a new array with the desired size and copy the items you need as appropriate  Here s code to remove an item from an array   lt System Runtime CompilerServices Extension   gt    Function RemoveAt Of T  ByVal arr As T    ByVal index As Integer  As T       Dim uBound   arr GetUpperBound 0      Dim lBound   arr GetLowerBound 0      Dim arrLen   uBound - lBound      If index  lt  lBound OrElse index  gt  uBound Then         Throw New ArgumentOutOfRangeException            String Format  quot Index must be from  0  to  1   quot   lBound  uBound        Else          create an array 1 element less than the input array         Dim outArr arrLen - 1  As T          copy the first part of the input array         Array Copy arr  0  outArr  0  index           then copy the second part of the input array         Array Copy arr  index   1  outArr  index  uBound - index           Return outArr     End If End Function  You can use it as such  Module Module1      Sub Main           Dim arr   New String     quot abc quot    quot mno quot    quot xyz quot           arr RemoveAt 1      End Sub End Module  The code above removes the second element   quot mno quot    which has an index of 1  from the array  You need to be developing in  NET 3 5 or higher in order to use the extension method  If you re using  NET 2 0 or 3 0  you can call the method as such arr   RemoveAt arr  1   I hope this is what you need  Update After running tests based on ToolMakerSteve s comment it appears the initial code does not modify the array you want to update because of the ByVal used in the function s declaration  However  writing code like arr   arr RemoveAt 1  or arr   RemoveAt arr  1  does modify the array because it reassigns the modified array to the original  Find below the updated method  subroutine  for removing an element from an array   lt System Runtime CompilerServices Extension   gt    Public Sub RemoveAt Of T  ByRef arr As T    ByVal index As Integer      Dim uBound   arr GetUpperBound 0      Dim lBound   arr GetLowerBound 0      Dim arrLen   uBound - lBound      If index  lt  lBound OrElse index  gt  uBound Then         Throw New ArgumentOutOfRangeException            String Format  quot Index must be from  0  to  1   quot   lBound  uBound        Else          create an array 1 element less than the input array         Dim outArr arrLen - 1  As T          copy the first part of the input array         Array Copy arr  0  outArr  0  index           then copy the second part of the input array         Array Copy arr  index   1  outArr  index  uBound - index           arr   outArr     End If End Sub  Usage of the method is similar to the original  except there is no return value this time so trying to assign an array from the return value will not work because nothing is returned  Dim arr   New String     quot abc quot    quot mno quot    quot xyz quot   arr RemoveAt 1     Output    quot abc quot    quot mno quot    works on  NET 3 5 and higher  RemoveAt arr  1    Output    quot abc quot    quot mno quot    works on all versions of  NET fx  arr   arr RemoveAt 1    will not work  no return value arr   RemoveAt arr  1   will not work  no return value  Note   I use a temporary array for the process because it makes my intentions clear and that is exactly what VB NET does behind the scenes when you do Redim Preserve   If you would like to modify the array in-place using Redim Preserve  see ToolmakerSteve s answer   The RemoveAt methods written here are extension methods  In order for them to work  you will have to paste them in a Module  Extension methods will not work in VB NET if they are placed in a Class   Important If you will be modifying your array with lots of  removes   it is highly recommended to use a different data structure such as List Of T  as suggested by other answerers to this question

User · Answer

One line using LINQ   Dim arr   As String     uno    dos    tres    cuatro    cinco   Dim indx As Integer   2 arr   arr Where Function item  index  index  lt  gt  indx  ToArray  arr     uno    dos    cuatro    cinco     Remove first element   arr   arr Skip 1  ToArray   Remove last element   arr   arr Take arr length - 1  ToArray

User · Answer

Yes  you can delete an element from an array  Here is an extension method that moves the elements as needed  then resizes the array one shorter     Remove element at index  index   Result is one element shorter    Similar to List RemoveAt  but for arrays   lt System Runtime CompilerServices Extension   gt    Public Sub RemoveAt Of T  ByRef a   As T  ByVal index As Integer        Move elements after  index  down 1 position      Array Copy a  index   1  a  index  UBound a  - index        Shorten by 1 element      ReDim Preserve a UBound a  - 1  End Sub   Usage examples  assuming array starting with index 0    Dim a   As String     Albert    Betty    Carlos    David   a RemoveAt 0       Remove first element   gt    Betty    Carlos    David   a RemoveAt 1       Remove second element   gt    Betty    David   a RemoveAt UBound a        Remove last element   gt    Betty     Removing First or Last element is common  so here are convenience routines for doing so  I like code that expresses my intent more readably     lt System Runtime CompilerServices Extension   gt    Public Sub DropFirstElement Of T  ByRef a   As T      a RemoveAt 0  End Sub   lt System Runtime CompilerServices Extension   gt    Public Sub DropLastElement Of T  ByRef a   As T      a RemoveAt UBound a   End Sub   Usage   a DropFirstElement   a DropLastElement     And as Heinzi said  if you find yourself doing this  instead use List Of T   if possible  List already has  RemoveAt  subroutine  and other routines useful for inserting deleting elements

User · Answer

This may be a lazy man s solution  but can t you just delete the contents of the index you want removed by reassigning their values to 0 or    and then ignore skip these empty array elements instead of recreating and copying arrays on and off

User · Answer

If the array is a string array you are able to then do the following   AlphaSplit    a b c  Split      MaxIndex     AlphaSplit GetUpperBound 0  AlphaSplit   AlphaSplit Where Function item  index  index  lt  gt  MaxIndex  ToArray AlphaJoin    String Join      PublishRouteSplit

[vb.net] How can I delete an item from an array in VB.NET?

Examples related to vb.net

Examples related to arrays