change array size

Question

Is it possible to change an array size after declaration  If not  is there any alternative to arrays  I do not want to create an array with a size of 1000  but I do not know the size of the array when I m creating it

User · Answer

Use a List lt T gt  instead  For instance  instead of an array of ints  private int    myIntegers   new int 1000     use  private List lt int gt   myIntegers   new List lt int gt       later   myIntegers Add 1

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If you really need to get it back into an array I find it easiest to convert the array to a list  expand the list then convert it back to an array           string   myArray   new string 1    Element One               Convert it to a list         List lt string gt  resizeList   myArray ToList               Add some elements         resizeList Add  Element Two               Back to an array         myArray   resizeList ToArray               myArray has grown to two elements

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This worked well for me to create a dynamic array from a class array   var s   0  var songWriters   new SongWriterDetails 1   foreach  var contributor in Contributors        Array Resize ref songWriters  s         songWriters s    new SongWriterDetails        songWriters s  DisplayName   contributor Name      songWriters s  PartyId   contributor Id      s

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private void HandleResizeArray                 int   aa   new int 2           aa 0    0          aa 1    1           aa   MyResizeArray aa           aa   MyResizeArray aa              private int   MyResizeArray int   aa                Array Resize ref aa  aa GetUpperBound 0    2           aa aa GetUpperBound 0     aa GetUpperBound 0           return aa

User · Answer

In C   arrays cannot be resized dynamically       One approach is to use System Collections ArrayList instead of a native array  Another  faster  solution is to re-allocate the array with a different size and to copy the contents of the old array to the new array   The generic function resizeArray  below  can be used to do that     public static System Array ResizeArray  System Array oldArray  int newSize                int oldSize   oldArray Length        System Type elementType   oldArray GetType   GetElementType          System Array newArray   System Array CreateInstance elementType newSize          int preserveLength   System Math Min oldSize newSize          if  preserveLength  gt  0        System Array Copy  oldArray newArray preserveLength         return newArray           public static void Main                       int   a    1 2 3           a    int   ResizeArray a 5           a 3    4          a 4    5           for  int i 0  i lt a Length  i                  System Console WriteLine  a i

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Use a List  where T is any type or Object  when you want to add remove data  since resizing arrays is expensive  You can read more about Arrays considered somewhat harmful whereas a List can be added to New records can be appended to the end  It adjusts its size as needed    A List can be initalized in following ways  Using collection initializer   List lt string gt  list1   new List lt string gt           carrot        fox        explorer       Using var keyword with collection initializer   var list2   new List lt string gt           carrot        fox        explorer       Using new array as parameter   string   array      carrot    fox    explorer     List lt string gt  list3   new List lt string gt  array     Using capacity in constructor and assign   List lt string gt  list4   new List lt string gt  3   list4 Add null      Add empty references   Not Recommended  list4 Add null   list4 Add null   list4 0     carrot      Assign those references  list4 1     fox   list4 2     explorer     Using Add method for each element   List lt string gt  list5   new List lt string gt     list5 Add  carrot    list5 Add  fox    list5 Add  explorer      Thus for an Object List you can allocate and assign the properties of objects inline with the List initialization  Object initializers and collection initializers share similar syntax   class Test       public int A   get  set        public string B   get  set        Initialize list with collection initializer   List lt Test gt  list1   new List lt Test gt          new Test    A   1  B    Jessica        new Test    A   2  B    Mandy        Initialize list with new objects   List lt Test gt  list2   new List lt Test gt     list2 Add new Test     A   3  B    Sarah      list2 Add new Test     A   4  B    Melanie

User · Answer

Use System Collections Generic List

User · Answer

Use a generic List  System Collections Generic List

User · Answer

In case you cannot use Array Reset  the variable is not local  then Concat  amp  ToArray helps   anObject anArray Concat new string     newArrayItem    ToArray

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In C   Array Resize is the simplest method to resize any array to new size  e g    Array Resize lt LinkButton gt  ref area  size     Here  i want to resize the array size of LinkButton array    lt LinkButton gt    specifies the array type ref area   ref is a keyword and  area  is the array name size   new size array

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You can use Array Resize   in  net 3 5 and higher   This method allocates a new array with the specified size  copies elements from the old array to the new one  and then replaces the old array with the new one   So you will need the memory available for both arrays as this probably uses Array Copy under the covers

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No  try using a strongly typed List instead   For example   Instead of using    int   myArray   new int 2   myArray 0    1  myArray 1    2    You could do this   List lt int gt  myList   new List lt int gt     myList Add 1   myList Add 2     Lists use arrays to store the data so you get the speed benefit of arrays with the convenience of a LinkedList by being able to add and remove items without worrying about having to manually change its size   This doesn t mean an array s size  in this instance  a List  isn t changed though - hence the emphasis on the word manually   As soon as your array hits its predefined size  the JIT will allocate a new array on the heap that is twice the size and copy your existing array across

User · Answer

Yes  it is possible to resize an array  For example   int   arr   new int 5      increase size to 10 Array Resize ref arr  10      decrease size to 3 Array Resize ref arr  3     If you create an array with CreateInstance   method  the Resize   method is not working  For example      create an integer array with size of 5 var arr   Array CreateInstance typeof int   5      this not work Array Resize ref arr  10     The array size is not dynamic  even we can resize it  If you want a dynamic array  I think we can use generic List instead   var list   new List lt int gt        add any item to the list list Add 5   list Add 8   list Add 12      we can remove it easily as well list Remove 5   foreach var item in list      Console WriteLine item

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Used this approach for array of bytes   Initially   byte   bytes   new byte 0     Whenever required  Need to provide original length for extending    Array Resize lt byte gt  ref bytes  bytes Length   requiredSize     Reset   Array Resize lt byte gt  ref bytes  0     Typed List Method  Initially   List lt byte gt  bytes   new List lt byte gt       Whenever required   bytes AddRange new byte length      Release Clear   bytes Clear

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You can use Array Resize    documented in MSDN   But yeah  I agree with Corey  if you need a dynamically sized data structure  we have Lists for that   Important  Array Resize   doesn t resize the array  the method name is misleading   it creates a new array and only replaces the reference you passed to the method   An example   var array1   new byte 10   var array2   array1  Array Resize lt byte gt  ref array1  20       Now     array1 Length is 20    array2 Length is 10    Two different arrays

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