How to delete an element from an array in C

Question

Lets say I have this array   int   numbers    1  3  4  9  2     How can I delete an element by  name     lets say number 4   Even ArrayList didn t help to delete   string strNumbers     1  3  4  9  2   ArrayList numbers   new ArrayList strNumbers Split new char              numbers RemoveAt numbers IndexOf 4    foreach  var n in numbers        Response Write n

User · Answer

You can also convert your array to a list and call remove on the list  You can then convert back to your array   int   numbers    1  3  4  9  2   var numbersList   numbers ToList    numbersList Remove 4

User · Answer

Balabaster s answer is correct if you want to remove all instances of the element  If you want to remove only the first one  you would do something like this   int   numbers     1  3  4  9  2  4    int numToRemove   4  int firstFoundIndex   Array IndexOf numbers  numToRemove   if  numbers  gt   0        numbers   numbers Take firstFoundIndex  Concat numbers Skip firstFoundIndex   1   ToArray

User · Answer

If you want to remove all instances of 4 without needing to know the index   LINQ    NET Framework 3 5   int   numbers     1  3  4  9  2    int numToRemove   4  numbers   numbers Where val   gt  val    numToRemove  ToArray      Non-LINQ    NET Framework 2 0   static bool isNotFour int n        return n    4     int   numbers     1  3  4  9  2    numbers   Array FindAll numbers  isNotFour  ToArray      If you want to remove just the first instance   LINQ    NET Framework 3 5   int   numbers     1  3  4  9  2  4    int numToRemove   4  int numIndex   Array IndexOf numbers  numToRemove   numbers   numbers Where  val  idx    gt  idx    numIndex  ToArray      Non-LINQ    NET Framework 2 0   int   numbers     1  3  4  9  2  4    int numToRemove   4  int numIdx   Array IndexOf numbers  numToRemove   List lt int gt  tmp   new List lt int gt  numbers   tmp RemoveAt numIdx   numbers   tmp ToArray      Edit  Just in case you hadn t already figured it out  as Malfist pointed out  you need to be targetting the  NET Framework 3 5 in order for the LINQ code examples to work   If you re targetting 2 0 you need to reference the Non-LINQ examples

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If you want to remove all instances of 4 without needing to know the index   LINQ    NET Framework 3 5   int   numbers     1  3  4  9  2    int numToRemove   4  numbers   numbers Where val   gt  val    numToRemove  ToArray      Non-LINQ    NET Framework 2 0   static bool isNotFour int n        return n    4     int   numbers     1  3  4  9  2    numbers   Array FindAll numbers  isNotFour  ToArray      If you want to remove just the first instance   LINQ    NET Framework 3 5   int   numbers     1  3  4  9  2  4    int numToRemove   4  int numIndex   Array IndexOf numbers  numToRemove   numbers   numbers Where  val  idx    gt  idx    numIndex  ToArray      Non-LINQ    NET Framework 2 0   int   numbers     1  3  4  9  2  4    int numToRemove   4  int numIdx   Array IndexOf numbers  numToRemove   List lt int gt  tmp   new List lt int gt  numbers   tmp RemoveAt numIdx   numbers   tmp ToArray      Edit  Just in case you hadn t already figured it out  as Malfist pointed out  you need to be targetting the  NET Framework 3 5 in order for the LINQ code examples to work   If you re targetting 2 0 you need to reference the Non-LINQ examples

User · Answer

You can also convert your array to a list and call remove on the list  You can then convert back to your array   int   numbers    1  3  4  9  2   var numbersList   numbers ToList    numbersList Remove 4

User · Answer

You can do in this way   int   numbers   1 3 4 9 2        List lt int gt  lst numbers   new List lt int gt  numbers   int required number   4  int i   0  foreach  int number in lst numbers                      if number    required number                break            i      lst numbers RemoveAt i   numbers   lst numbers ToArray

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The code that is written in the question has a bug in it  Your arraylist contains strings of   1    3    4    9  and   2   note the spaces   So IndexOf 4  will find nothing because 4 is an int  and even  tostring  would convert it to of  4  and not   4   and nothing will get removed   An arraylist is the correct way to go to do what you want

User · Answer

Removing from an array itself is not simple  as you then have to deal with resizing   This is one of the great advantages of using something like a List lt int gt  instead   It provides Remove RemoveAt in 2 0  and lots of LINQ extensions for 3 0     If you can  refactor to use a List lt  gt  or similar

User · Answer

As a generic extension  2 0-compatible   using System Collections Generic  public static class Extensions                                                                                          Removes all instances of  itemToRemove  from array  original         Returns the new array  without modifying  original  directly         Net2 0-compatible     public static T   RemoveFromArray lt T gt   this T   original  T itemToRemove              int numIdx   System Array IndexOf original  itemToRemove           if  numIdx    -1  return original          List lt T gt  tmp   new List lt T gt  original           tmp RemoveAt numIdx           return tmp ToArray              Usage   int   numbers    1  3  4  9  2   numbers   numbers RemoveFromArray 4

User · Answer

Balabaster s answer is correct if you want to remove all instances of the element  If you want to remove only the first one  you would do something like this   int   numbers     1  3  4  9  2  4    int numToRemove   4  int firstFoundIndex   Array IndexOf numbers  numToRemove   if  numbers  gt   0        numbers   numbers Take firstFoundIndex  Concat numbers Skip firstFoundIndex   1   ToArray

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int   numbers     1  3  4  9  2    numbers   numbers Except new int   4   ToArray

User · Answer

The code that is written in the question has a bug in it  Your arraylist contains strings of   1    3    4    9  and   2   note the spaces   So IndexOf 4  will find nothing because 4 is an int  and even  tostring  would convert it to of  4  and not   4   and nothing will get removed   An arraylist is the correct way to go to do what you want

User · Answer

If you want to remove all instances of 4 without needing to know the index   LINQ    NET Framework 3 5   int   numbers     1  3  4  9  2    int numToRemove   4  numbers   numbers Where val   gt  val    numToRemove  ToArray      Non-LINQ    NET Framework 2 0   static bool isNotFour int n        return n    4     int   numbers     1  3  4  9  2    numbers   Array FindAll numbers  isNotFour  ToArray      If you want to remove just the first instance   LINQ    NET Framework 3 5   int   numbers     1  3  4  9  2  4    int numToRemove   4  int numIndex   Array IndexOf numbers  numToRemove   numbers   numbers Where  val  idx    gt  idx    numIndex  ToArray      Non-LINQ    NET Framework 2 0   int   numbers     1  3  4  9  2  4    int numToRemove   4  int numIdx   Array IndexOf numbers  numToRemove   List lt int gt  tmp   new List lt int gt  numbers   tmp RemoveAt numIdx   numbers   tmp ToArray      Edit  Just in case you hadn t already figured it out  as Malfist pointed out  you need to be targetting the  NET Framework 3 5 in order for the LINQ code examples to work   If you re targetting 2 0 you need to reference the Non-LINQ examples

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I posted my solution here   This is a way to delete an array element without copying to another array - just in frame of the same array instance       public static void RemoveAt lt T gt  ref T   arr  int index                for  int a   index  a  lt  arr Length - 1  a                             moving elements downwards  to fill the gap at  index              arr a    arr a   1                        finally  let s decrement Array s size by one         Array Resize ref arr  arr Length - 1

User · Answer

Removing from an array itself is not simple  as you then have to deal with resizing   This is one of the great advantages of using something like a List lt int gt  instead   It provides Remove RemoveAt in 2 0  and lots of LINQ extensions for 3 0     If you can  refactor to use a List lt  gt  or similar

User · Answer

Removing from an array itself is not simple  as you then have to deal with resizing   This is one of the great advantages of using something like a List lt int gt  instead   It provides Remove RemoveAt in 2 0  and lots of LINQ extensions for 3 0     If you can  refactor to use a List lt  gt  or similar

User · Answer

I posted my solution here   This is a way to delete an array element without copying to another array - just in frame of the same array instance       public static void RemoveAt lt T gt  ref T   arr  int index                for  int a   index  a  lt  arr Length - 1  a                             moving elements downwards  to fill the gap at  index              arr a    arr a   1                        finally  let s decrement Array s size by one         Array Resize ref arr  arr Length - 1

User · Answer

The code that is written in the question has a bug in it  Your arraylist contains strings of   1    3    4    9  and   2   note the spaces   So IndexOf 4  will find nothing because 4 is an int  and even  tostring  would convert it to of  4  and not   4   and nothing will get removed   An arraylist is the correct way to go to do what you want

User · Answer

Balabaster s answer is correct if you want to remove all instances of the element  If you want to remove only the first one  you would do something like this   int   numbers     1  3  4  9  2  4    int numToRemove   4  int firstFoundIndex   Array IndexOf numbers  numToRemove   if  numbers  gt   0        numbers   numbers Take firstFoundIndex  Concat numbers Skip firstFoundIndex   1   ToArray

User · Answer

You can do in this way   int   numbers   1 3 4 9 2        List lt int gt  lst numbers   new List lt int gt  numbers   int required number   4  int i   0  foreach  int number in lst numbers                      if number    required number                break            i      lst numbers RemoveAt i   numbers   lst numbers ToArray

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To remove items from string based on Dictionary key values    VB net code   Dim stringArr As String      file1 file2 file3 file4 file5 file6  Split    c   Dim test As Dictionary Of String  String    New Dictionary Of String  String   test Add  file3    description    test Add  file5    description    stringArr   stringArr Except test Keys  ToArray

User · Answer

Balabaster s answer is correct if you want to remove all instances of the element  If you want to remove only the first one  you would do something like this   int   numbers     1  3  4  9  2  4    int numToRemove   4  int firstFoundIndex   Array IndexOf numbers  numToRemove   if  numbers  gt   0        numbers   numbers Take firstFoundIndex  Concat numbers Skip firstFoundIndex   1   ToArray

User · Answer

As a generic extension  2 0-compatible   using System Collections Generic  public static class Extensions                                                                                          Removes all instances of  itemToRemove  from array  original         Returns the new array  without modifying  original  directly         Net2 0-compatible     public static T   RemoveFromArray lt T gt   this T   original  T itemToRemove              int numIdx   System Array IndexOf original  itemToRemove           if  numIdx    -1  return original          List lt T gt  tmp   new List lt T gt  original           tmp RemoveAt numIdx           return tmp ToArray              Usage   int   numbers    1  3  4  9  2   numbers   numbers RemoveFromArray 4

User · Answer

Removing from an array itself is not simple  as you then have to deal with resizing   This is one of the great advantages of using something like a List lt int gt  instead   It provides Remove RemoveAt in 2 0  and lots of LINQ extensions for 3 0     If you can  refactor to use a List lt  gt  or similar

User · Answer

If you want to remove all instances of 4 without needing to know the index   LINQ    NET Framework 3 5   int   numbers     1  3  4  9  2    int numToRemove   4  numbers   numbers Where val   gt  val    numToRemove  ToArray      Non-LINQ    NET Framework 2 0   static bool isNotFour int n        return n    4     int   numbers     1  3  4  9  2    numbers   Array FindAll numbers  isNotFour  ToArray      If you want to remove just the first instance   LINQ    NET Framework 3 5   int   numbers     1  3  4  9  2  4    int numToRemove   4  int numIndex   Array IndexOf numbers  numToRemove   numbers   numbers Where  val  idx    gt  idx    numIndex  ToArray      Non-LINQ    NET Framework 2 0   int   numbers     1  3  4  9  2  4    int numToRemove   4  int numIdx   Array IndexOf numbers  numToRemove   List lt int gt  tmp   new List lt int gt  numbers   tmp RemoveAt numIdx   numbers   tmp ToArray      Edit  Just in case you hadn t already figured it out  as Malfist pointed out  you need to be targetting the  NET Framework 3 5 in order for the LINQ code examples to work   If you re targetting 2 0 you need to reference the Non-LINQ examples

User · Answer

To remove items from string based on Dictionary key values    VB net code   Dim stringArr As String      file1 file2 file3 file4 file5 file6  Split    c   Dim test As Dictionary Of String  String    New Dictionary Of String  String   test Add  file3    description    test Add  file5    description    stringArr   stringArr Except test Keys  ToArray

User · Answer

int   numbers     1  3  4  9  2    numbers   numbers Except new int   4   ToArray

User · Answer

The code that is written in the question has a bug in it  Your arraylist contains strings of   1    3    4    9  and   2   note the spaces   So IndexOf 4  will find nothing because 4 is an int  and even  tostring  would convert it to of  4  and not   4   and nothing will get removed   An arraylist is the correct way to go to do what you want

[c#] How to delete an element from an array in C#

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