Convert.ToString() to binary format not working as expected

Question

int i = 20;
string output = Convert.ToString(i, 2); // Base2 formatting
i = -20;
output = Convert.ToString(i, 2);

Value   Expected                       


        

Answer 1

Here is a routine I wrote that does what the original questioner wanted. A mere 5 years too late!

/// 
Convert a number into a string of bits
/// Value to convert
/// Minimum number of bits, usually a multiple of 4
/// Value must be convertible to long
/// Value must be convertible to long
/// 
public static string ShowBits(this T value, int minBits)
{
    long x = Convert.ToInt64(value);
    string retVal = Convert.ToString(x, 2);
    if (retVal.Length > minBits) retVal = Regex.Replace(retVal, @"^1+", "1");   // Replace leading 1s with a single 1 - can pad as needed below
    if (retVal.Length < minBits) retVal = new string(x < 0 ? '1' : '0', minBits - retVal.Length) + retVal;  // Pad on left with 0/1 as appropriate
    return retVal;
}