how to diffrence strings in c#

Aren't those characters you're using in Delphi?

In .NET you can use those two methods, to check the integer representation of the string. But, lets change them to characters, and you'll see that this same method works here too.

// condition...
if('1' <= '2') {
   // what to do
   Console.WriteLine("Works");
}

.. above code printed "Works" in the Console, here[^] give it a try yourself.

You can use them as variables too, such as

// variable initialization and declaration
char a = '1';
char b = '2';
// condition
if(a <= b) {
   // what to do...
   Console.WriteLine("Works");
}

Wasn't it unfair of you, to use strings and not use Convert or Int.TryParse? Try this dotnetperl[^] link for more.