It's a textbook example. You can explain work of it.

Question

сlass C
{
int i;
public C (int i) { this. i = i;}
public static explicit operator C (string s>
{
return new C (int. Parse(s)) ;
}
}

object o = "1';
dynamic d =" 2";
var c1 = (C) o; //error

var c2 = (C) d;

Answer 1

Explicit operator used to convert something to class where you declare it.
In this case operator c will convert string to int.
But here object o = "1'; there are single quot instead of dual used, this is probably why var c1 = (C) o; statement marked with error.