I would like to programmatically add or remove some elements to a string array in C#, but still keeping the items I had before, a bit like the VB function ReDim Preserve.
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8What have you tried? This question due to it's basic nature will probably have 50 answers in 3 minutes. Google would have been just as helpful.Erik Philips– Erik Philips2012-03-05 17:17:45 +00:00Commented Mar 5, 2012 at 17:17
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2vb's redim preserve was and is evil. You're are always, without exception, better off using a collection type. And it's not often I will make absolute declarations like that.Joel Coehoorn– Joel Coehoorn2012-03-05 17:19:33 +00:00Commented Mar 5, 2012 at 17:19
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2Minus 5 seems a little harsh for this question. I struggled with this concept and transition upon moving from VBA to C#.Brad– Brad2012-03-05 17:51:30 +00:00Commented Mar 5, 2012 at 17:51
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1Duplicate of stackoverflow.com/questions/202813/…Omar– Omar2012-03-05 18:03:10 +00:00Commented Mar 5, 2012 at 18:03
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10 Answers
The obvious suggestion would be to use a List<string> instead, which you will have already read from the other answers. This is definitely the best way in a real development scenario.
Of course, I want to make things more interesting (my day that is), so I will answer your question directly.
Here are a couple of functions that will Add and Remove elements from a string[]...
string[] Add(string[] array, string newValue){
int newLength = array.Length + 1;
string[] result = new string[newLength];
for(int i = 0; i < array.Length; i++)
result[i] = array[i];
result[newLength -1] = newValue;
return result;
}
string[] RemoveAt(string[] array, int index){
int newLength = array.Length - 1;
if(newLength < 1)
{
return array;//probably want to do some better logic for removing the last element
}
//this would also be a good time to check for "index out of bounds" and throw an exception or handle some other way
string[] result = new string[newLength];
int newCounter = 0;
for(int i = 0; i < array.Length; i++)
{
if(i == index)//it is assumed at this point i will match index once only
{
continue;
}
result[newCounter] = array[i];
newCounter++;
}
return result;
}
2 Comments
Cippo
Thanks everybody for the time spent on my question and for having answered to it!!!! Everyone of you has been useful to me!!! Thanks in particular to you, your answer is the one I was looking for!!!
Olivier Jacot-Descombes
Note that a
List<T> does exactly the same internally as ReDim Preserve would do on an array. In fact List<T> stores things in an internal array and resizes it automatically when required. This makes ReDim Preserve obsolete even in VB.If you really won't (or can't) use a generic collection instead of your array, Array.Resize is c#'s version of redim preserve:
var oldA = new [] {1,2,3,4};
Array.Resize(ref oldA,10);
foreach(var i in oldA) Console.WriteLine(i); //1 2 3 4 0 0 0 0 0 0
Comments
Don't use an array - use a generic List<T> which allows you to add items dynamically.
If this is not an option, you can use Array.Copy or Array.CopyTo to copy the array into a larger array.
Comments
Since arrays implement IEnumerable<T> you can use Concat:
string[] strArr = { "foo", "bar" };
strArr = strArr.Concat(new string[] { "something", "new" });
Or what would be more appropriate would be to use a collection type that supports inline manipulation.
Comments
Use List<string> instead of string[].
List allows you to add and remove items with good performance.
Comments
One liner:
string[] items = new string[] { "a", "b" };
// this adds "c" to the string array:
items = new List<string>(items) { "c" }.ToArray();
1 Comment
MemeDeveloper
Neat. Learn something every day.
What's abaut this one:
List<int> tmpList = intArry.ToList();
tmpList.Add(anyInt);
intArry = tmpList.ToArray();
Comments
You can use a generic collection, like List<>
List<string> list = new List<string>();
// add
list.Add("element");
// remove
list.Remove("element");
1 Comment
Brad
The equivalent concept of removing an element from as list as from an array is probably through the
RemoveAt method because it takes in index value. Remove removes the first occurrence which might be desired but seems trickier to control.You can use this snippet:
static void Main(string[] args)
{
Console.WriteLine("Enter number:");
int fnum = 0;
bool chek = Int32.TryParse(Console.ReadLine(),out fnum);
Console.WriteLine("Enter number:");
int snum = 0;
chek = Int32.TryParse(Console.ReadLine(),out snum);
Console.WriteLine("Enter number:");
int thnum = 0;
chek = Int32.TryParse(Console.ReadLine(),out thnum);
int[] arr = AddToArr(fnum,snum,thnum);
IOrderedEnumerable<int> oarr = arr.OrderBy(delegate(int s)
{
return s;
});
Console.WriteLine("Here your result:");
oarr.ToList().FindAll(delegate(int num) {
Console.WriteLine(num);
return num > 0;
});
}
public static int[] AddToArr(params int[] arr) {
return arr;
}
I hope this will help to you, just change the type
