convert javascript function to C# (conversion question)

since i'm poor with javascript I would like someone to convert this small function to C# code for me..

var cn = 0;
function C(i,s)
{ 
   return s.charCodeAt(i) ^ (cn|1) ^ ((cn++ & 1)?i:0) 开发者_运维技巧^ 0x55 
}

I would really appreciate your help. thanks in advance :)

private static int cn = 0;
public static int C(int i, string s)
{
    return s[i] ^ (cn | 1) ^ (((cn++ & 1) == 1) ? i : 0) ^ 0x55;
}

private static int cn = 0;
public static int C(int i, string s)
{ 
   return ((byte)s[i]) ^ (cn|1) ^ ((cn++ & 1) != 0 ? i:0) ^ 0x55;
}

That's written with the assumption that the function is going into a class as a static function, so you would call it like this:

MessageBox.Show(MyType.C(0, "test")); //Output: 32

If you remove the static keyword, you can call it as an instance method:

MyType something = new MyType();
MessageBox.Show(something.C(0, "test"); //Output: 32