C # my views on the value type and reference type

The biggest difference between the value type and the reference type is that the storage space allocated by the value type is in the stack, and the Space analyzed by the reference type is in the heap memory.

So what types are value types and reference types?

Value Type: primitive type, enumeration type, and struct type.

Reference Type: Class, String, standard module, interface, array, and delegate.

So how can we differentiate between value types and reference types based on their table types?

Solution 1: Use the system type attribute to determine

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1. Public boolIsvaluetype <t> ()

2. {

3. Return typeof(T). isvaluetype;

4. }

 

Solution 2: Use whether it can be empty or not to judge (trick)

Value reference cannot be empty by default. For example, int I = NULL; a prompt is displayed in the vs compiler.

The reference type can be null by default. For example, string STR = NULL is correct.

Value reference and type reference must be distinguished during programming. They are also often used to evaluate the basic skills of a programmer. They appear in interview questions or exams. How can they be investigated?

Based on: value-type variables directly contain their data, while reference-type variables store references to their data, which is called an object. For the reference type, two variables may reference the same object. Therefore, operations on one variable may affect the objects referenced by another variable.

You may encounter the following code to write the final output:

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2. Public voidPrinttheresultstring ()

4. {

6. Console. Writeline ("String type value assignment");

8. StringSTR ="Init";

10. Console. Writeline ("Original :"+ Str );

12. Process (STR );

14. Console. Writeline ("Result :"+ Str );

16. }

18. Private voidProcess (StringStr)

20. {

22. STR ="Changed";

24. }

 

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1.   Public void  printtheresultint () 

2. {

3.   console . writeline ( "int type value assignment" ); 

4.   int  I = 0; 

5.   console . writeline ( "Original:"  + I); 

6.  process (I); 

7.   console . writeline ( "Result:"  + I); 

8. }

9.   private void  process ( int  I) 

10. {

11.  I = 2; 

12. }

 

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2. Public voidPrinttheresultdatetime ()

4. {

6. Console. Writeline ("Datetime type value assignment");

8. DatetimeDt =Datetime. Parse ("2000-01-01");

10. Console. Writeline ("Original :"+ Dt. tostring ("Yyyy-mm-dd"));

12. Process (DT );

14. Console. Writeline ("Result :"+ Dt. tostring ("Yyyy-mm-dd"));

16. }

18. Private voidProcess (DatetimeDT)

20. {

22. Dt =Datetime. Parse ("2001-01-01");

24. }

 

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2. Public voidPrinttheresultarraylist ()

4. {

6. Console. Writeline ("Arraylist type assignment");

8. ArraylistArraylist =NewArraylist();

10. Console. Writeline ("Original :"+ Arraylist. Count );

12. Process (arraylist );

14. Console. Writeline ("Result :"+ Arraylist. Count );

16. }

18. Private voidProcess (ArraylistArraylist)

20. {

22. Arraylist. Add ("1");

26. }

 

In the preceding four paragraphs, what are the output results?

It can be seen that, except for the value assignment of the arraylist type, the values are changed, and the other values are kept in the initial state. Do string, Int, and datetime values all belong to the value type?

With solution 1, you can easily find that string is a reference type, and it is a spy in the value type. String is a reference type, but its usage is exactly the same as that of the value type. It is a pseudo-value type fabricated.

Int is a primitive type, datetime is a struct type, and they are indeed a real value type.

 

That's all. Let's talk about the empty type next time.