Find largest binary gap of a number N improved
If I were in a position to be unaware of them and this is the code I
  managed to write, what's your thoughts on it?



No need to call ToCharArray() because you can iterate over the chars of a string as well
By using an else if instead of the second if you won't need to check for toChar[i] == '0' but basically you only need a else. 
Using a foreach loop instead of a for loop seems more natural for this task.  
The returning of the answer can be simply return answer;  
Because ToString(int, 2) strips leading '0' you can remove both current and previous.


Summing up it could look like so  

public static int FindGap(int number)
{
    int maxGap = 0;
    int answer = 0;

    foreach(var c in Convert.ToString(number, 2))
    {
        if (c == '1')
        {
            if (answer &lt; maxGap)
            {
                answer = maxGap;
            }
            maxGap = 0;
        }
        else
        {
            maxGap++;
        }
    }
    return answer;
}