int array to string

Question

In C#, I have an array of ints, containing digits only. I want to convert this array to string.

Array example:

int[] arr = {0,1,2,3,0,1};

How can I convert this to a string formatted as: "012301"?

Answer 1

 String.Join("", new List<int>(array).ConvertAll(i => i.ToString()).ToArray());

Answer 2

string result = arr.Aggregate("", (s, i) => s + i.ToString());

(Disclaimer: If you have a lot of digits (hundreds, at least) and you care about performance, I suggest eschewing this method and using a StringBuilder, as in JaredPar's answer.)

Answer 3

You can do:

 int[] arr = {0,1,2,3,0,1};
 string results = string.Join("",arr.Select(i => i.ToString()).ToArray());

That gives you your results.

Answer 4

string s = string.Concat(arr.Cast<object>().ToArray());

Answer 5

To avoid the creation of an extra array you could do the following.

var builder = new StringBuilder();
Array.ForEach(arr, x => builder.Append(x));
var res = bulider.ToString();

Answer 6

string.Join("", (from i in arr select i.ToString()).ToArray())

In the .NET 4.0 the string.Join can use an IEnumerable<string> directly:

string.Join("", from i in arr select i.ToString())

Answer 7

I like using StringBuilder with Aggregate(). The "trick" is that Append() returns the StringBuilder instance itself:

var sb = arr.Aggregate( new StringBuilder(), ( s, i ) => s.Append( i ) );
var result = sb.ToString();

Answer 8

I realize my opinion is probably not the popular one, but I guess I have a hard time jumping on the Linq-y band wagon. It's nifty. It's condensed. I get that and I'm not opposed to using it where it's appropriate. Maybe it's just me, but I feel like people have stopped thinking about creating utility functions to accomplish what they want and instead prefer to litter their code with (sometimes) excessively long lines of Linq code for the sake of creating a dense 1-liner.

I'm not saying that any of the Linq answers that people have provided here are bad, but I guess I feel like there is the potential that these single lines of code can start to grow longer and more obscure as you need to handle various situations. What if your array is null? What if you want a delimited string instead of just purely concatenated? What if some of the integers in your array are double-digit and you want to pad each value with leading zeros so that the string for each element is the same length as the rest?

Taking one of the provided answers as an example:

        result = arr.Aggregate(string.Empty, (s, i) => s + i.ToString());

If I need to worry about the array being null, now it becomes this:

        result = (arr == null) ? null : arr.Aggregate(string.Empty, (s, i) => s + i.ToString());

If I want a comma-delimited string, now it becomes this:

        result = (arr == null) ? null : arr.Skip(1).Aggregate(arr[0].ToString(), (s, i) => s + "," + i.ToString());

This is still not too bad, but I think it's not obvious at a glance what this line of code is doing.

Of course, there's nothing stopping you from throwing this line of code into your own utility function so that you don't have that long mess mixed in with your application logic, especially if you're doing it in multiple places:

    public static string ToStringLinqy<T>(this T[] array, string delimiter)
    {
        // edit: let's replace this with a "better" version using a StringBuilder
        //return (array == null) ? null : (array.Length == 0) ? string.Empty : array.Skip(1).Aggregate(array[0].ToString(), (s, i) => s + "," + i.ToString());
        return (array == null) ? null : (array.Length == 0) ? string.Empty : array.Skip(1).Aggregate(new StringBuilder(array[0].ToString()), (s, i) => s.Append(delimiter).Append(i), s => s.ToString());
    }

But if you're going to put it into a utility function anyway, do you really need it to be condensed down into a 1-liner? In that case why not throw in a few extra lines for clarity and take advantage of a StringBuilder so that you're not doing repeated concatenation operations:

    public static string ToStringNonLinqy<T>(this T[] array, string delimiter)
    {
        if (array != null)
        {
            // edit: replaced my previous implementation to use StringBuilder
            if (array.Length > 0)
            {
                StringBuilder builder = new StringBuilder();

                builder.Append(array[0]);
                for (int i = 1; i < array.Length; i++)
                {
                    builder.Append(delimiter);
                    builder.Append(array[i]);
                }

                return builder.ToString()
            }
            else
            {
                return string.Empty;
            }
        }
        else
        {
            return null;
        }
    }

And if you're really so concerned about performance, you could even turn it into a hybrid function that decides whether to do string.Join or to use a StringBuilder depending on how many elements are in the array (this is a micro-optimization, not worth doing in my opinion and possibly more harmful than beneficial, but I'm using it as an example for this problem):

    public static string ToString<T>(this T[] array, string delimiter)
    {
        if (array != null)
        {
            // determine if the length of the array is greater than the performance threshold for using a stringbuilder
            // 10 is just an arbitrary threshold value I've chosen
            if (array.Length < 10)
            {
                // assumption is that for arrays of less than 10 elements
                // this code would be more efficient than a StringBuilder.
                // Note: this is a crazy/pointless micro-optimization.  Don't do this.
                string[] values = new string[array.Length];

                for (int i = 0; i < values.Length; i++)
                    values[i] = array[i].ToString();

                return string.Join(delimiter, values);
            }
            else
            {
                // for arrays of length 10 or longer, use a StringBuilder
                StringBuilder sb = new StringBuilder();

                sb.Append(array[0]);
                for (int i = 1; i < array.Length; i++)
                {
                    sb.Append(delimiter);
                    sb.Append(array[i]);
                }

                return sb.ToString();
            }
        }
        else
        {
            return null;
        }
    }

For this example, the performance impact is probably not worth caring about, but the point is that if you are in a situation where you actually do need to be concerned with the performance of your operations, whatever they are, then it will most likely be easier and more readable to handle that within a utility function than using a complex Linq expression.

That utility function still looks kind of clunky. Now let's ditch the hybrid stuff and do this:

    // convert an enumeration of one type into an enumeration of another type
    public static IEnumerable<TOut> Convert<TIn, TOut>(this IEnumerable<TIn> input, Func<TIn, TOut> conversion)
    {
        foreach (TIn value in input)
        {
            yield return conversion(value);
        }
    }

    // concatenate the strings in an enumeration separated by the specified delimiter
    public static string Delimit<T>(this IEnumerable<T> input, string delimiter)
    {
        IEnumerator<T> enumerator = input.GetEnumerator();

        if (enumerator.MoveNext())
        {
            StringBuilder builder = new StringBuilder();

            // start off with the first element
            builder.Append(enumerator.Current);

            // append the remaining elements separated by the delimiter
            while (enumerator.MoveNext())
            {
                builder.Append(delimiter);
                builder.Append(enumerator.Current);
            }

            return builder.ToString();
        }
        else
        {
            return string.Empty;
        }
    }

    // concatenate all elements
    public static string ToString<T>(this IEnumerable<T> input)
    {
        return ToString(input, string.Empty);
    }

    // concatenate all elements separated by a delimiter
    public static string ToString<T>(this IEnumerable<T> input, string delimiter)
    {
        return input.Delimit(delimiter);
    }

    // concatenate all elements, each one left-padded to a minimum length
    public static string ToString<T>(this IEnumerable<T> input, int minLength, char paddingChar)
    {
        return input.Convert(i => i.ToString().PadLeft(minLength, paddingChar)).Delimit(string.Empty);
    }

Now we have separate and fairly compact utility functions, each of which are arguable useful on their own.

Ultimately, my point is not that you shouldn't use Linq, but rather just to say don't forget about the benefits of creating your own utility functions, even if they are small and perhaps only contain a single line that returns the result from a line of Linq code. If nothing else, you'll be able to keep your application code even more condensed than you could achieve with a line of Linq code, and if you are using it in multiple places, then using a utility function makes it easier to adjust your output in case you need to change it later.

For this problem, I'd rather just write something like this in my application code:

        int[] arr = { 0, 1, 2, 3, 0, 1 };

        // 012301
        result = arr.ToString<int>();

        // comma-separated values
        // 0,1,2,3,0,1
        result = arr.ToString(",");

        // left-padded to 2 digits
        // 000102030001
        result = arr.ToString(2, '0');

Answer 9

The most effecient way is not to convert each int to a string, but rather create one string out of an array of chars. Then the garbage collection only has one new temp object to worry about.

int[] arr = {0,1,2,3,0,1};
string result = new string(Array.ConvertAll<int,char>(arr, x => Convert.ToChar(x + 0x30)));