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ReDim Preserve(vb6)  in  C#

Posted on 2004-09-13
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Last Modified: 2008-01-09
Hi

how can i do like "vb6"   (ReDim PreserveArray)   but  in  C#
not with ArrayList

regards
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Question by:Kobi55
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6 Comments
 
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Expert Comment

by:tzxie2000
ID: 12043447
If you just want to change the array length please test code below

int [] a=int[16];
a=int[32];
a[31]=12;

you can create a new int array and assigned to a.
you can change int to other types

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Expert Comment

by:a_goat
ID: 12044428
VB's ReDim Preserve compiles to the following

int[] a = int[16];

// This is the redim stuff
int[] b = int[16];
for (int I = 0; I < a.Length && I < b.Length; I++)
    b[I] = a[I];
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Expert Comment

by:a_goat
ID: 12044434
Sorry, to add to that...


int[] a = int[16];

// This is the redim stuff
int[] b = int[16];
for (int I = 0; I < a.Length && I < b.Length; I++)
    b[I] = a[I];

a = b;
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Assisted Solution

by:a_goat
a_goat earned 125 total points
ID: 12044450
Bah, I'm a lazy typist

int[] a = int[16];
// Populate a

// This is the redim stuff
int[] b = int[32];
for (int I = 0; I < a.Length && I < b.Length; I++)
    b[I] = a[I];

a = b;


At this point, a will be an int array with 32 slots, containing whatever data was in a when it only had 16 slots.  This will also cover cases where you decrease the number of slots.
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Assisted Solution

by:tzxie2000
tzxie2000 earned 125 total points
ID: 12044555
if you want remain data in array
use this improve my code may be more quick

int [] a=int[16];
//doing something
a=int[32];

Array.Copy(a,b,a.Length>b.Length?b.Length:a.Length);
a[31]=12;
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Accepted Solution

by:
AvonWyss earned 250 total points
ID: 12044568
Use the following method:

      public static Array ReDimPreserve(Array input, int size) {
            Array result=(Array)Activator.CreateInstance(input.GetType(), new object[] {size});
            Array.Copy(input, result, Math.Min(input.Length, result.Length));
            return result;
      }

And then you use it like this:

      int [] a=int[16];
      a=(int[])ReDimArrayPreserve(a, 32);

Note that this works for arrays of any type, not only ints. because of that, you need to typecast the returned array into the array type you're expecting.
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