Comparing strings and get the first place where they vary from eachother

Question

I want to get the first place where 2 string vary from each other. example: for these two strings: \"AAAB\" \"AAAAC\"

I want to get the result 4.

How do i d

Answer 1

string one = "AAAB";
string two = "AAAAC";

int found = -1;
int index = 0;
while (one != two && found == -1 && one.Length > index && two.Length > index)
{
    if (one[index] != two[index]) found = index;
    index++;
}