array of string with unknown size

开发者_StackOverflow

How is an array of string where you do not know where the array size in c#.NET?

String[] array = new String[]; // this does not work

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Is there a specific reason why you need to use an array? If you don't know the size before hand you might want to use List<String>

List<String> list = new List<String>();

list.Add("Hello");
list.Add("world");
list.Add("!");

Console.WriteLine(list[2]);

Will give you an output of

!

MSDN - List(T) for more information

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You don't have to specify the size of an array when you instantiate it.

You can still declare the array and instantiate it later. For instance:

string[] myArray;

...

myArray = new string[size];

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You can't create an array without a size. You'd need to use a list for that.

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you can declare an empty array like below

String[] arr = new String[]{}; // declare an empty array
String[] arr2 = {"A", "B"}; // declare and assign values to an array
arr = arr2; // assign valued array to empty array

you can't assign values to above empty array like below

arr[0] = "A"; // you can't do this

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As others have mentioned you can use a List<String> (which I agree would be a better choice). In the event that you need the String[] (to pass to an existing method that requires it for instance) you can always retrieve an array from the list (which is a copy of the List<T>'s inner array) like this:

String[] s = yourListOfString.ToArray();

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I think you may be looking for the StringBuilder class. If not, then the generic List class in string form:

List<string> myStringList = new List<string();
myStringList.Add("Test 1");
myStringList.Add("Test 2");

Or, if you need to be absolutely sure that the strings remain in order:

Queue<string> myStringInOriginalOrder = new Queue<string();
myStringInOriginalOrder.Enqueue("Testing...");
myStringInOriginalOrder.Enqueue("1...");
myStringInOriginalOrder.Enqueue("2...");
myStringInOriginalOrder.Enqueue("3...");

Remember, with the List class, the order of the items is an implementation detail and you are not guaranteed that they will stay in the same order you put them in.

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I suppose that the array size if a computed value.

int size = ComputeArraySize();

// Then

String[] array = new String[size]; 

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Can you use a List strings and then when you are done use strings.ToArray() to get the array of strings to work with?

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If you will later know the length of the array you can create the initial array like this:

String[] array;

And later when you know the length you can finish initializing it like this

array = new String[42];

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If you want to use array without knowing the size first you have to declare it and later you can instantiate it like

string[] myArray;
...
...
myArray=new string[someItems.count];

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string[ ] array = {};

// it is not null instead it is empty.

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string foo = "Apple, Plum, Cherry";

string[] myArr = null;

myArr = foo.Split(',');