What is difference between variable.toString() method and Convert.toString(variable) in asp.net using c#.

The basic difference  is  "variable.toString()" does not handle NULL value it throws null exception error but Convert.toString(variable) handle NULL value  even if variable value becomes null.

Example:-

// throws a null exception error

        string str;

        int i = null;

        str = i.ToString();

 // return empty string values for str and does not throw exception

        string str;

        int i = null;

        str = Convert.ToString(i);