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I am trying to add 2 new array items to existing string array. I achieved the result but I am sure this is not the right way to do .
How can I add items to a string array.
string[] sg = {"x", "y" };
string[] newSg = {"z", "w"};
string[] updatedSg = new string[sg.Length+newSg.Length];
for (int i = 0; i < sg.Length; i++)
{
updatedSg[i] = sg[i];
}
for (int i = 0; i < newSg.Length; i++)
{
updatedSg[sg.Length+i] = newSg[i];
}
You cannot add items to an array. You can use another container type, like a List, or you can create a new array with more elements and copy the old elements over. But you cannot add elements to an array and you cannot remove elements from an array. The number of elements in an array is fixed.
You can Concat two arrays into one by using Linq:
string[] updatedSg = sg
.Concat(newSg)
.ToArray();
An alternative is using List<String> for updatedSg collection type instead of array:
List<string> updatedSg = new List<string>(sg);
updatedSg.AddRange(newSg);
If you insist on updating an existing array then in general case you can have:
// imagine we don't know the actual size
string[] updatedSg = new string[0];
// add sg.Length items to the array
Array.Resize(ref updatedSg, sg.Length + updatedSg.Length);
// copy the items
for (int i = 0; i < sg.Length; ++i)
updatedSg[updatedSg.Length - sg.Length + i - 1] = sg[i];
// add updatedSg.Length items to the array
Array.Resize(ref updatedSg, newSg.Length + updatedSg.Length);
// copy the items
for (int i = 0; i < newSg.Length; ++i)
updatedSg[updatedSg.Length - newSg.Length + i - 1] = newSg[i];
If i have to add items to an array dynamically, i would use a List instead of an Array (Lists have an Add() method very useful). You could even convert it to an array at the end of the process (with ToArray() method). But you can also use methods like Concat() as mentioned above.
Using CopyTo()
var updatedSg = new string[sg.Length + newSg.Length];
sg.CopyTo(updatedSg, 0);
sgNew.CopyTo(updatedSg, sg.Length);
As answered here
https://stackoverflow.com/a/1547276/7070657
Or per somebody's suggestion:
var temp = x.Length;
Array.Resize(ref x, x.Length + y.Length);
y.CopyTo(x, temp); // x and y instead of sg and sgNew
I have the following object[] array:
array[0] = obj_1;
array[1] = obj_2;
array[2] = obj_3;
array[3] = NULL;
array[4] = NULL;
And I need to insert another element between the array[1] and array[2] like this:
array[0] = obj_1;
array[1] = obj_2;
array[2] = obj_New;
array[3] = obj_3;
array[4] = NULL;
I can't use List before someone suggest. Any ideas of how can I do that?
There is no direct way. You need to move the elements first, and then set the value at desired index.
Below is sample snippet (without any array index checks)
void InsertItem(object[] array, int index, object val)
{
for(int i=index;i<array.Length;i++)
{
array[i] = array[i-1];
}
array[index] = val;
}
Do note that Array once created are allocated contigigous location, and are of fixed size. They cannot be arbitrary moved.
If you require various such operations, i would suggest linked list data structure.
From your post, it sounds like you want to pop the last item off the array and not the first one.
If so, like Tilak has suggested, the simplest way is to take/determine the index where the item has to be inserted and move the items from current position to the next subsequent position and finally add the new item in the given index. You would want to watch out for what happens if the array is already full, do you want to drop the last item or not?
We can optimize a bit in Tilak's code, by not overwriting the array[index] item twice, once in loop and once outside.
I will do it a bit different, I will start from end and go up, so you can avoid a temp variable.
void InsertItem(object[] array, int index, object val)
{
for(int i=array.Length - 1; i > index; i--)
{
array[i] = array[i-1];
}
array[index] = val;
}
Like others have already said, List or LinkedList will be a better choice.
I just needed a light to do it. I used Tilak's example as my base and I did the following code (With some more things like add in the end of the list and with a starting empty array):
object[] array = new object[0];
public void Insert(int index, object val)
{
Array.Resize(ref array, array.Length + 1);
if (index >= array.Length-1)
{
array[array.Length - 1] = val;
return;
}
for (int i = 0; i < array.Length; i++)
{
if (index == i)
{
for (int idx = array.Length; idx > index; idx--)
{
array[idx-1] = array[idx-2];
}
array[i] = val;
return;
}
}
}
It is completely functional and the Array.Resize activates every time that I insert something so that my array will always be with the exactly number of slots that I need.
What I'm doing wrong? What I'm trying to do is to add to existing array linesLat values but for next value to insert in linesLat is to take previous from array and summ stepLong. But at the end getting error.
static void Main(string[] args)
{
var stepLong = (10.6237 - 5.9216) / 1000;
var stepLat = (47.7245 - 45.7368) / 1000;
double[] linesLat = { 45.7368 };
double[] linesLong = { 5.9216 };
for (var i = 1; i <= 999; )
{
linesLat[i] = linesLat[i - 1] + stepLat; // throws an error
i++;
}
}
Additional information: Index was outside the bounds of the array.
You should really go back to basics.
Array as a limited size and it will be on the exact size you declare it to be.
In your case you allocated two arrays in the size of 1 (Due to explicit initialization).
double[] linesLat = { 45.7368 }; // Size 1
double[] linesLong = { 5.9216 }; // Size 1
Meaning you can't loop from [0, 999], when you will try to take the value from position 1 (Because C# arrays are zero based; The first element is in the 0 place and not 1) you will get a KABOOM meaning you will get an exception telling you, your index (probably 1) is outside of the legal array bounds.
Solution: You should change your solution to declare a bigger array as #i_a_joref suggested.
var linesLat = new double[1000];
linesLat[0] = 45.7368;
Additionally, your loop can be written more properly:
for (var i = 1; i < linesLat.Length; i++)
{
linesLat[i] = linesLat[i - 1] + stepLat;
}
Possible solution variation for your problem.
If the only goal is to get the sum of the last formula, than array is redundant.
double sumOfFormula = 45.7368;
for (var i = 0; i < 1000; i++) // Will run [0, 999] 1000 iterations
{
sumOfFormula += stepLat;
}
Console.WriteLine("Sum: ", sumOfFormula);
You declared linesLat as an array of size one. If you want to put 999+ elements in it, you need to declare a bigger array.
Your array has a lenght of 1, and you try to iterate up to 999.
You need to instanciate your array with a lengh of 999
double[] linesLat = new double[999];
Your array have size of 1 and in for loop you are trying to access indexes greater then array size.
Just change:
double[] linesLat = { 45.7368 };
to:
double[] linesLat = new double[1000];
linesLat[0] = 45.7368;
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.
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<byte>(ref array1, 20);
// Now:
// array1.Length is 20
// array2.Length is 10
// Two different arrays.
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<int> myList = new List<int>();
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.
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)
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<int>();
// 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);
}
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 > 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<a.Length; i++)
System.Console.WriteLine (a[i]);
}
Used this approach for array of bytes:
Initially:
byte[] bytes = new byte[0];
Whenever required (Need to provide original length for extending):
Array.Resize<byte>(ref bytes, bytes.Length + requiredSize);
Reset:
Array.Resize<byte>(ref bytes, 0);
Typed List Method
Initially:
List<byte> bytes = new List<byte>();
Whenever required:
bytes.AddRange(new byte[length]);
Release/Clear:
bytes.Clear()
Use System.Collections.Generic.List
Use a List<T> instead. For instance, instead of an array of ints
private int[] _myIntegers = new int[1000];
use
private List<int> _myIntegers = new List<int>();
later
_myIntegers.Add(1);
In C#, Array.Resize is the simplest method to resize any array to new size, e.g.:
Array.Resize<LinkButton>(ref area, size);
Here, i want to resize the array size of LinkButton array:
<LinkButton> = specifies the array type
ref area = ref is a keyword and 'area' is the array name
size = new size array
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;
}
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<string> resizeList = myArray.ToList();
// Add some elements
resizeList.Add("Element Two");
// Back to an array
myArray = resizeList.ToArray();
// myArray has grown to two elements.
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<string> list1 = new List<string>()
{
"carrot",
"fox",
"explorer"
};
Using var keyword with collection initializer.
var list2 = new List<string>()
{
"carrot",
"fox",
"explorer"
};
Using new array as parameter.
string[] array = { "carrot", "fox", "explorer" };
List<string> list3 = new List<string>(array);
Using capacity in constructor and assign.
List<string> list4 = new List<string>(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<string> list5 = new List<string>();
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<Test> list1 = new List<Test>()
{
new Test(){ A = 1, B = "Jessica"},
new Test(){ A = 2, B = "Mandy"}
};
Initialize list with new objects.
List<Test> list2 = new List<Test>();
list2.Add(new Test() { A = 3, B = "Sarah" });
list2.Add(new Test() { A = 4, B = "Melanie" });
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++;
}
In case you cannot use Array.Reset (the variable is not local) then Concat & ToArray helps:
anObject.anArray.Concat(new string[] { newArrayItem }).ToArray();
Use a generic List (System.Collections.Generic.List).
Probably a really simple one this - I'm starting out with C# and need to add values to an array, for example:
int[] terms;
for(int runs = 0; runs < 400; runs++)
{
terms[] = runs;
}
For those who have used PHP, here's what I'm trying to do in C#:
$arr = array();
for ($i = 0; $i < 10; $i++) {
$arr[] = $i;
}
You can do this way -
int[] terms = new int[400];
for (int runs = 0; runs < 400; runs++)
{
terms[runs] = value;
}
Alternatively, you can use Lists - the advantage with lists being, you don't need to know the array size when instantiating the list.
List<int> termsList = new List<int>();
for (int runs = 0; runs < 400; runs++)
{
termsList.Add(value);
}
// You can convert it back to an array if you would like to
int[] terms = termsList.ToArray();
Edit: a) for loops on List<T> are a bit more than 2 times cheaper than foreach loops on List<T>, b) Looping on array is around 2 times cheaper than looping on List<T>, c) looping on array using for is 5 times cheaper than looping on List<T> using foreach (which most of us do).
Using Linq's method Concat makes this simple
int[] array = new int[] { 3, 4 };
array = array.Concat(new int[] { 2 }).ToArray();
result
3,4,2
If you're writing in C# 3, you can do it with a one-liner:
int[] terms = Enumerable.Range(0, 400).ToArray();
This code snippet assumes that you have a using directive for System.Linq at the top of your file.
On the other hand, if you're looking for something that can be dynamically resized, as it appears is the case for PHP (I've never actually learned it), then you may want to use a List instead of an int[]. Here's what that code would look like:
List<int> terms = Enumerable.Range(0, 400).ToList();
Note, however, that you cannot simply add a 401st element by setting terms[400] to a value. You'd instead need to call Add() like this:
terms.Add(1337);
By 2019 you can use Append, Prepend using LinQ in just one line
using System.Linq;
and then in NET 6.0:
terms = terms.Append(21);
or versions lower than NET 6.0
terms = terms.Append(21).ToArray();
Answers on how to do it using an array are provided here.
However, C# has a very handy thing called System.Collections
Collections are fancy alternatives to using an array, though many of them use an array internally.
For example, C# has a collection called List that functions very similar to the PHP array.
using System.Collections.Generic;
// Create a List, and it can only contain integers.
List<int> list = new List<int>();
for (int i = 0; i < 400; i++)
{
list.Add(i);
}
Using a List as an intermediary is the easiest way, as others have described, but since your input is an array and you don't just want to keep the data in a List, I presume you might be concerned about performance.
The most efficient method is likely allocating a new array and then using Array.Copy or Array.CopyTo. This is not hard if you just want to add an item to the end of the list:
public static T[] Add<T>(this T[] target, T item)
{
if (target == null)
{
//TODO: Return null or throw ArgumentNullException;
}
T[] result = new T[target.Length + 1];
target.CopyTo(result, 0);
result[target.Length] = item;
return result;
}
I can also post code for an Insert extension method that takes a destination index as input, if desired. It's a little more complicated and uses the static method Array.Copy 1-2 times.
Based on the answer of Thracx (I don't have enough points to answer):
public static T[] Add<T>(this T[] target, params T[] items)
{
// Validate the parameters
if (target == null) {
target = new T[] { };
}
if (items== null) {
items = new T[] { };
}
// Join the arrays
T[] result = new T[target.Length + items.Length];
target.CopyTo(result, 0);
items.CopyTo(result, target.Length);
return result;
}
This allows to add more than just one item to the array, or just pass an array as a parameter to join two arrays.
You have to allocate the array first:
int [] terms = new int[400]; // allocate an array of 400 ints
for(int runs = 0; runs < terms.Length; runs++) // Use Length property rather than the 400 magic number again
{
terms[runs] = value;
}
int ArraySize = 400;
int[] terms = new int[ArraySize];
for(int runs = 0; runs < ArraySize; runs++)
{
terms[runs] = runs;
}
That would be how I'd code it.
C# arrays are fixed length and always indexed. Go with Motti's solution:
int [] terms = new int[400];
for(int runs = 0; runs < 400; runs++)
{
terms[runs] = value;
}
Note that this array is a dense array, a contiguous block of 400 bytes where you can drop things. If you want a dynamically sized array, use a List<int>.
List<int> terms = new List<int>();
for(int runs = 0; runs < 400; runs ++)
{
terms.Add(runs);
}
Neither int[] nor List<int> is an associative array -- that would be a Dictionary<> in C#. Both arrays and lists are dense.
You can't just add an element to an array easily. You can set the element at a given position as fallen888 outlined, but I recommend to use a List<int> or a Collection<int> instead, and use ToArray() if you need it converted into an array.
If you really need an array the following is probly the simplest:
using System.Collections.Generic;
// Create a List, and it can only contain integers.
List<int> list = new List<int>();
for (int i = 0; i < 400; i++)
{
list.Add(i);
}
int [] terms = list.ToArray();
one approach is to fill an array via LINQ
if you want to fill an array with one element
you can simply write
string[] arrayToBeFilled;
arrayToBeFilled= arrayToBeFilled.Append("str").ToArray();
furthermore, If you want to fill an array with multiple elements you can use the
previous code in a loop
//the array you want to fill values in
string[] arrayToBeFilled;
//list of values that you want to fill inside an array
List<string> listToFill = new List<string> { "a1", "a2", "a3" };
//looping through list to start filling the array
foreach (string str in listToFill){
// here are the LINQ extensions
arrayToBeFilled= arrayToBeFilled.Append(str).ToArray();
}
Array Push Example
public void ArrayPush<T>(ref T[] table, object value)
{
Array.Resize(ref table, table.Length + 1); // Resizing the array for the cloned length (+-) (+1)
table.SetValue(value, table.Length - 1); // Setting the value for the new element
}
int[] terms = new int[10]; //create 10 empty index in array terms
//fill value = 400 for every index (run) in the array
//terms.Length is the total length of the array, it is equal to 10 in this case
for (int run = 0; run < terms.Length; run++)
{
terms[run] = 400;
}
//print value from each of the index
for (int run = 0; run < terms.Length; run++)
{
Console.WriteLine("Value in index {0}:\t{1}",run, terms[run]);
}
Console.ReadLine();
/*Output：
Value in index 0: 400
Value in index 1: 400
Value in index 2: 400
Value in index 3: 400
Value in index 4: 400
Value in index 5: 400
Value in index 6: 400
Value in index 7: 400
Value in index 8: 400
Value in index 9: 400
*/
If you don't know the size of the Array or already have an existing array that you are adding to. You can go about this in two ways. The first is using a generic List<T>:
To do this you will want convert the array to a var termsList = terms.ToList(); and use the Add method. Then when done use the var terms = termsList.ToArray(); method to convert back to an array.
var terms = default(int[]);
var termsList = terms == null ? new List<int>() : terms.ToList();
for(var i = 0; i < 400; i++)
termsList.Add(i);
terms = termsList.ToArray();
The second way is resizing the current array:
var terms = default(int[]);
for(var i = 0; i < 400; i++)
{
if(terms == null)
terms = new int[1];
else
Array.Resize<int>(ref terms, terms.Length + 1);
terms[terms.Length - 1] = i;
}
If you are using .NET 3.5 Array.Add(...);
Both of these will allow you to do it dynamically. If you will be adding lots of items then just use a List<T>. If it's just a couple of items then it will have better performance resizing the array. This is because you take more of a hit for creating the List<T> object.
Times in ticks:
3 items
Array Resize Time: 6
List Add Time: 16
400 items
Array Resize Time: 305
List Add Time: 20
I will add this for a another variant. I prefer this type of functional coding lines more.
Enumerable.Range(0, 400).Select(x => x).ToArray();
You can't do this directly. However, you can use Linq to do this:
List<int> termsLst=new List<int>();
for (int runs = 0; runs < 400; runs++)
{
termsLst.Add(runs);
}
int[] terms = termsLst.ToArray();
If the array terms wasn't empty in the beginning, you can convert it to List first then do your stuf. Like:
List<int> termsLst = terms.ToList();
for (int runs = 0; runs < 400; runs++)
{
termsLst.Add(runs);
}
terms = termsLst.ToArray();
Note: don't miss adding 'using System.Linq;' at the begaining of the file.
This seems like a lot less trouble to me:
var usageList = usageArray.ToList();
usageList.Add("newstuff");
usageArray = usageList.ToArray();
Just a different approach:
int runs = 0;
bool batting = true;
string scorecard;
while (batting = runs < 400)
scorecard += "!" + runs++;
return scorecard.Split("!");
int[] terms = new int[400];
for(int runs = 0; runs < 400; runs++)
{
terms[runs] = value;
}
static void Main(string[] args)
{
int[] arrayname = new int[5];/*arrayname is an array of 5 integer [5] mean in array [0],[1],[2],[3],[4],[5] because array starts with zero*/
int i, j;
/*initialize elements of array arrayname*/
for (i = 0; i < 5; i++)
{
arrayname[i] = i + 100;
}
/*output each array element value*/
for (j = 0; j < 5; j++)
{
Console.WriteLine("Element and output value [{0}]={1}",j,arrayname[j]);
}
Console.ReadKey();/*Obtains the next character or function key pressed by the user.
The pressed key is displayed in the console window.*/
}
/*arrayname is an array of 5 integer*/
int[] arrayname = new int[5];
int i, j;
/*initialize elements of array arrayname*/
for (i = 0; i < 5; i++)
{
arrayname[i] = i + 100;
}
To add the list values to string array using C# without using ToArray() method
List<string> list = new List<string>();
list.Add("one");
list.Add("two");
list.Add("three");
list.Add("four");
list.Add("five");
string[] values = new string[list.Count];//assigning the count for array
for(int i=0;i<list.Count;i++)
{
values[i] = list[i].ToString();
}
Output of the value array contains:
one
two
three
four
five
You can do this is with a list. here is how
List<string> info = new List<string>();
info.Add("finally worked");
and if you need to return this array do
return info.ToArray();
Here is one way how to deal with adding new numbers and strings to Array:
int[] ids = new int[10];
ids[0] = 1;
string[] names = new string[10];
do
{
for (int i = 0; i < names.Length; i++)
{
Console.WriteLine("Enter Name");
names[i] = Convert.ToString(Console.ReadLine());
Console.WriteLine($"The Name is: {names[i]}");
Console.WriteLine($"the index of name is: {i}");
Console.WriteLine("Enter ID");
ids[i] = Convert.ToInt32(Console.ReadLine());
Console.WriteLine($"The number is: {ids[i]}");
Console.WriteLine($"the index is: {i}");
}
} while (names.Length <= 10);