Conversion of System.Array to List

Conversion of System.Array to List

Save yourself some pain...

using System.Linq;

int[] ints = new [] { 10, 20, 10, 34, 113 };

List<int> lst = ints.OfType<int>().ToList(); // this isn't going to be fast.

Can also just...

List<int> lst = new List<int> { 10, 20, 10, 34, 113 };

or...

List<int> lst = new List<int>();
lst.Add(10);
lst.Add(20);
lst.Add(10);
lst.Add(34);
lst.Add(113);

or...

List<int> lst = new List<int>(new int[] { 10, 20, 10, 34, 113 });

or...

var lst = new List<int>();
lst.AddRange(new int[] { 10, 20, 10, 34, 113 });

How do I convert an Array to a List object in C#?

List<object> list = myArray.Cast<Object>().ToList();

If the type of the array elements is a reference type, you can leave out the .Cast<object>() since C#4 added interface co-variance i.e. an IEnumerable<SomeClass> can be treated as an IEnumerable<object>.

List<object> list = myArray.ToList<object>();

Conversion from System.Array to List string using LINQ, need to keep empty values

try this:

xmlData.AddRange(myvals.Cast<object>().Select(O => O == null ? 
                                                      string.Empty : 
                                                      O.ToString()).ToList());

Convert array of strings to List string

Just use this constructor of List<T>. It accepts any IEnumerable<T> as an argument.

string[] arr = ...
List<string> list = new List<string>(arr);

Converting array to list in Java

In your example, it is because you can't have a List of a primitive type. In other words, List<int> is not possible.

You can, however, have a List<Integer> using the Integer class that wraps the int primitive. Convert your array to a List with the Arrays.asList utility method.

Integer[] numbers = new Integer[] { 1, 2, 3 };
List<Integer> list = Arrays.asList(numbers);

See this code run live at IdeOne.com.

how to convert an array of objects to list

Just pass the array in List constructor.

IList<PersonData> aPerList = new List<PersonData>(aPersonDataArr);

To Convert back:

PersonData[] array = aPerList.ToArray();

If you don't want to use LINQ ToArray then Use List.CopyTo:

PersonData[] newArray = new PersonData[aPerList.Count];
aPerList.CopyTo(arrArray,0);

convert List Object to System.Array[]

Use a little bit more LINQ Select will help you do the trick:

Array[] Values = val.Select(x => (Array)x).ToArray();

Note: every x must be convertible to Array.

That said, Array itself is already an array. Array[] seems to be Array of Arrays to me and the data types of the elements are not strongly typed.

Array a = new int[10]; //this is ok
Array b = new string[10]; //this is also ok

Thus, your Array[] may contain any strongly-typed arrays. {int[], string[], double[]} and so on...

Unless it is what you really want, it seems to be not so safe design - IMHO.

Convert array of Strings to list of Integers?

You only need to stream once.

Instead of using int Integer::parseInt(String s), you should use Integer Integer::valueOf(String s), so you don't have to call boxed() or rely on auto-boxing.

Then use collect(Collectors.toList()) directly, instead of creating intermediate array first.

List<Integer> allAnswerList = Arrays.stream(allAnswers)    // stream of String
                                    .map(Integer::valueOf) // stream of Integer
                                    .collect(Collectors.toList());

Array to List or List to Array, which conversion is faster?

Arrays.asList is faster because it does not copy data - it returns an object wrapping the array passed to it, and implementing the List interface. Collection.toArray() copies the data to the array, so it runs in O(N) instead of O(1).

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