How do I convert an Int to a String in C# without using ToString()?

Something like this:

public string IntToString(int a)
{    
    var chars = new[] { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9" };
    var str = string.Empty;
    if (a == 0)
    {
        str = chars[0];
    }
    else if (a == int.MinValue)
    {
        str = "-2147483648";
    }
    else
    {
        bool isNegative = (a < 0);
        if (isNegative)
        {
            a = -a;
        }

        while (a > 0)
        {
            str = chars[a % 10] + str;
            a /= 10;
        }

        if (isNegative)
        {
            str = "-" + str;
        }
    }

    return str;
}

---

Update: Here's another version which is shorter and should perform much better, since it eliminates all string concatenation in favor of manipulating a fixed-length array. It supports bases up to 16, but it would be easy to extend it to higher bases. It could probably be improved further:

public string IntToString(int a, int radix)
{
    var chars = "0123456789ABCDEF".ToCharArray();
    var str = new char[32]; // maximum number of chars in any base
    var i = str.Length;
    bool isNegative = (a < 0);
    if (a <= 0) // handles 0 and int.MinValue special cases
    {
        str[--i] = chars[-(a % radix)];
        a = -(a / radix);
    }

    while (a != 0)
    {
        str[--i] = chars[a % radix];
        a /= radix;
    }

    if (isNegative)
    {
        str[--i] = '-';
    }

    return new string(str, i, str.Length - i);
}

This is the solution I always use:

    public static string numberBaseChars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";

    public static string IntToStringWithBase(int n, int b) {
        return IntToStringWithBase(n, b, 1);
    }

    public static string IntToStringWithBase(int n, int b, int minDigits) {
        if (minDigits < 1) minDigits = 1;
        if (n == 0) return new string('0', minDigits);
        string s = "";
        if ((b < 2) || (b > numberBaseChars.Length)) return s;
        bool neg = false;
        if ((b == 10) && (n < 0)) { neg = true; n = -n; }
        uint N = (uint)n;
        uint B = (uint)b;
        while ((N > 0) | (minDigits-- > 0)) {
            s = numberBaseChars[(int)(N % B)] + s;
            N /= B;
        }
        if (neg) s = "-" + s;
        return s;
    }

This looks quite complicated but has the following features:

• Supports radix 2 to 36
• Handles negative values
• Optional total number of digits

I am not truly convinced the concatenation operator + calls ToString, but if that is indeed true, you can avoid those two by doing something like the following:

if (a == 0) return "0";   

/* Negative maxint doesn't have a corresponding positive value, so handle it
 * as a special case. Thanks to @Daniel for pointing this out.
 */
if (a == 0x80000000) return "-2147483648";

List<char> l = new List<char>();
bool negative = false;

if (a < 0) 
{
    negative = true;
    a *= -1;
}

while (a > 0)
{
    l.Add('0' + (char)(a % 10));
    a /= 10;
}

if (negative) l.Add('-');

l.Reverse();

return new String(l.ToArray());