c# - 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 do it in C#?

Answer 1

.NET 4:

string a1 = "AAAB";
string a2 = "AAAAC";

int index = a1.Zip(a2, (c1, c2) => c1 == c2).TakeWhile(b => b).Count() + 1;