How to get the exact position of string one into string 2 c#

How to get the exact position of string one into string 2 c#

I have a string like this String Str1 ="44444444.44" and need the exact
position of string Str2= "." into Str1
Actually I'm using String.Compare(Str1,Str2), but it return some extrange
results, what is the proper function in C# to do This?