c# - How can I join int[] to a character-separated string in .NET?

Question

I have an array of integers:

int[] number = new int[] { 2,3,6,7 };

What is the easiest way of converting these into a single string where the numbers are separated by a character (like: "2,3,6,7")?

I'm using C# and .NET 3.5.

Answer 1

var ints = new int[] {1, 2, 3, 4, 5};
var result = string.Join(",", ints.Select(x => x.ToString()).ToArray());
Console.WriteLine(result); // prints "1,2,3,4,5"

As of (at least) .NET 4.5,

var result = string.Join(",", ints.Select(x => x.ToString()).ToArray());

is equivalent to:

var result = string.Join(",", ints);

I see several solutions advertise usage of StringBuilder. Someone complains that the Join method should take an IEnumerable argument.

I'm going to disappoint you :) String.Join requires an array for a single reason - performance. The Join method needs to know the size of the data to effectively preallocate the necessary amount of memory.

Here is a part of the internal implementation of String.Join method:

// length computed from length of items in input array and length of separator
string str = FastAllocateString(length);
fixed (char* chRef = &str.m_firstChar) // note than we use direct memory access here
{
    UnSafeCharBuffer buffer = new UnSafeCharBuffer(chRef, length);
    buffer.AppendString(value[startIndex]);
    for (int j = startIndex + 1; j <= num2; j++)
    {
        buffer.AppendString(separator);
        buffer.AppendString(value[j]);
    }
}