How Can I Initialize Array Size During Run Time

Question

3.40/5 (2 votes)

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I Don't Know What Size Of Array is?

If I Am Creating an Array:

C#

int[] marks = new int[10];

In This Case If User Want Add More Than 10 , It Will Throw Error

And I Can't Use This One Also

C#

int [] marks = new int[]  { 99,  98, 92, 97, 95};

Posted 5-Nov-15 3:10am

Hitesh Jain

Updated 8-Nov-15 23:54pm

Leo Chapiro

v2

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4 solutions

Solution 4

Hello ,

Array.Resize function is there.

Try This,

C#

int[] marks = new int[10];
Array.Resize(ref marks,marks.length+1);

It will be Resize your array to +1 from the current length.

Posted 8-Nov-15 23:36pm

Mangal Deep Gupta

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Sergey Alexandrovich Kryukov · Accepted Answer · 2015-11-05T04:06:00

In addition to Solution 1:

Volkan Paksoy meant the generic class System.Collections.Generic.List<>:
https://msdn.microsoft.com/en-us/library/6sh2ey19%28v=vs.110%29.aspx[^].

Depending on what operations you really need to support, you may need other types of collections, but don't use obsolete ArrayList.

Now, closer to what you wanted to do you can do this, but don't:
https://msdn.microsoft.com/en-us/library/bb348051%28v=vs.110%29.aspx[^].

Why "big bold don't"? Read "Remarks" section. It would create a brand new array object each time you reallocate it, amd copy all data, but the effect would be miserable, at this cost, it is not even functionally acceptable. You have to decide how many elements to add; and it's bad to face a need for an arbitrary decision; then you add 10 and the user only uses 1, besides, you will have to maintain the number of actually uses elements, as opposed to allocated. Collections, collections, only collections.

By a similar reasons, never repeatedly concatenate "the same string", it's not the same. String is immutable. System.Text.StringBuilder, which can be considered as a mutable analog of string.

—SA

User 9557924 · Accepted Answer · 2015-11-05T03:27:00

Solution 1

You can use a List<int> instead of an array like this:

C#

var myList = new List<int>();

You can add or remove as many items you want at runtime. If you definitely need to get an array out of it you can convert it with ToArray method:

C#

var myArray = myList.ToArray();

Posted 5-Nov-15 3:27am

User 9557924

Updated 5-Nov-15 3:28am

v2

Comments

Sergey Alexandrovich Kryukov 5-Nov-15 10:07am

Yes, this is what the inquirer really needs (up-voted the answer), but I added some explanation and information, please see Solution 2.
—SA

Krunal Rohit · Accepted Answer · 2015-11-05T04:19:00

Solution 3

Well, you cant.
But you can convert your array to list and then append item to it.

Something like,

C#

int[] marks = new int[10];
// fill your array with the values
List<int> MarksList = new List<int>(marks);
marksList.Add(75);

Use this List<t> Constructor[^]

[Edit]
<int> tags removed

-KR

Posted 5-Nov-15 4:19am

Krunal Rohit

Updated 5-Nov-15 4:23am

v2

Comments

Philippe Mori 5-Nov-15 12:28pm

Why create an array? Use only a list (except if you already have some data that come in that format from elsewhere).

Krunal Rohit 5-Nov-15 23:37pm

Yes, but what if there's a dynamic change ?
Well, this is an alternative solution :)

-KR