String. Empty, "", null

1. null

The null keyword is a text value that does not reference any object's null reference. Null is the default value of the reference type variable. Then, only the referenced variable can be null. If int I = NULL, it is not possible because Int Is of the value type.

2., "" And string. Empty

Both are empty strings. But "" theoretically re-opens the memory space, and string. Empty points to a allocated memory space. But the optimizer will optimize it!

 

Several methods for determining as a Null String, in the order of performance from high to low:

S. Length = 0Better than S = string. Empty than S = ""

 

About string. the problem with empty and null is that both of them indicate null strings, and one of them focuses on string str1 = string. the difference between empty and string str2 = NULL. After this definition, str1 is an empty string, and the empty string is a special string, except that the value of this string is null, in the memory, there is an accurate point. String str2 = NULL. After this definition, only a reference to the string class is defined, and str2 does not point to any place, if it is not instantiated before use, an error will be reported.