How to convert string variable to int in c#?

There are three ways to convert a string into int type, see blow example 

string num="546323";

int a;

1) a = Convert.ToInt32(num);

2) a = int.Parse(num)

3) Third way is the best way to convert string into int. In this method try to convert string into int and if conversion successful then it return True and result in out parameter and if it fails then it returns False see below 

bool isNum;

string num="543568";

int res;

isNum=int.TryParse(num, out res);

now we can check isNum variable, if it's value is true that's mean that conversion is successful and it is False then it denotes conversion not successful means that string can't be converted into int.