Comparing

A < B < a < b

Case Sensitive

This method is overloaded and is case sensitive by default.

System.String.Compare(sText1, sText2) 

sText1 < sText2

System.String.Compare("aaa", "bbb") = -1 (less than zero) 

sText1 > sText2

System.String.Compare("bbb", "aaa") = 1 (greater than zero) 

sText1 = sText2

System.String.Compare("aaa", "aaa") = 0 

sText1 <> sText2

System.String.Compare("aaa", "AAA") = 

Case InSensitive

It is possible to compare strings and ignore the case

System.String.Compare(sText1, sText2, True) 

sText1 = sText2

System.String.Compare("aaa", "AAA", True) = 0 

Testing For Equality

There are two ways you can test to see if two strings are equal.
You can use the Equals method from one of the strings

string sFirstName; 
string sLastName; 
bequal = sFirstName.Equals(sLastName) 

Or you can pass both the strings to the String class method.

string sFirstName; 
string sLastName; 
bequal = System.String.Equals(FirstName, sLastName) 

VB.Net - Option Compare

By default this option is set to binary

This setting does not exist in C', because all string comparisons are case sensitive.
By default in VB string comparisons are not case sensitive