Question mark operator in C #

The question mark operator in C # has three functions:

 

First, a single question mark is used as a Trielement operator for conditional judgment.
This method can process some simple conditional statements with the if structure,
For example, the simple function of assigning values based on conditional results:

Int A = 4 ;
Int B = - 4 ;
Int C = B > 0 ? B:;

The aboveCodeIf the value of variable B is greater than 0, the value of B is assigned to C. Otherwise, the value of a is assigned to C.

 

Second, a single question mark is used as the identifier of the variable declared for the basic data type.
The structure of this method is as follows:

Int ? < Argument > = < Value > ;

In this way, the value of the basic data type can be assigned null.
For example:

Int I = Null ;

This code will return an error during compilation, and the code like the following can be executed normally:

Int ? I = Null ;

 

 

Third, double question marks are used as operators for condition judgment.
For example, to ensure that the value of a string object cannot be null, you can use the following method:

String Str1 = Null ;
String Str2 = Str1 ?? "" ;

The code above will automatically judge the value of the str1 object. If it is not null, assign the value of str1 to str2; otherwise, assign the null string to str2.