从对象转换为字符串时如何处理空异常？

Question

Just curious:

These lines throw Invalid Cast Exception : Unable to cast object of type 'System.Double' to type 'System.String'.

 Object obj = new object();
 obj = 20.09089;
 string value = (string)obj;

I receive the obj value from a library .

How to simply convert to string when we don't know the type of object while enumerating?

Answer 1

这就是为什么.net中的每个对象都具有ToString（）方法（从Object继承）的原因

string str = (obj == null) ? string.Empty : obj.ToString();

Answer 2

This is an boxing / unboxing issue.

20.09089 is a double by default. When you wanna unbox a primitive type from object , you need to unbox it the original type first .

Object obj = new object();
obj = 20.09089;
string value = ((double)obj).ToString();

or simplify;

Object obj = new object();
obj = 20.09089;
string value = obj.ToString();