How can I declare a variable with name "operator"?
public string operator;
you can use any reserved word by prefixing the name of your identifier with an @
: @operator
var @operator = "+";
var @event = new { name = "Burning man" };
var @var = 23;
var @enum = new List { 1, 2, 3 };
needless to say, this is not so much helping readability, but if you feel it fits your case, you can use it.
Use public string @operator
.
The @ prefix allows you to use reserved words as variable names.