easy and fast way to convert an int to binary?

var result = Convert.ToString(number, 2);

– Almost the only use for the (otherwise useless) Convert class.

Most ways will be better and faster than the function that you found. It's not a very good example on how to do the conversion.

The built in method Convert.ToString(num, base) is an obvious choice, but you can easily write a replacement if you need it to work differently.

This is a simple method where you can specify the length of the binary number:

public static string ToBin(int value, int len) {
   return (len > 1 ? ToBin(value >> 1, len - 1) : null) + "01"[value & 1];
}

It uses recursion, the first part (before the +) calls itself to create the binary representation of the number except for the last digit, and the second part takes care of the last digit.

Example:

Console.WriteLine(ToBin(42, 8));

Output:

00101010