A brief overview of value types and reference types in C#

Concept:

1. Value type: Data is stored in the stack of memory, and the data can be quickly accessed from the stack. Therefore, the value type represents the actual data.

2. Reference type: Represents a pointer or reference to data stored in the memory heap (including classes, interfaces, arrays and strings).

The value types defined in C# include primitive types (Sbyte, Byte, Short, Ushort, Int, Uint, Long, Ulong, Char, Float, Double, Bool, Decimal), enumeration (enum), and structure (struct)

Reference types include: classes, arrays, interfaces, delegates, strings, etc.

Difference:

The basic difference is how they are stored in memory. Value types only store values ​​in memory, and these value types are stored on the stack. Primitive data types (such as bool and int) belong to this type. The reference type memory unit only stores the address of the object in the memory heap, and the object itself is placed in the memory heap. If the value of the referenced value type is null, it means that no object is referenced.

The difference between heap and stack:

Heap and stack are two different concepts, and their storage locations in memory are also different.

Heap is generally used to store variables Length data, such as string type;

The stack is used to store fixed-length data, such as integer type data int (each int variable occupies four bytes). It can be known from the location of data storage that when a value variable is assigned to another value variable, two identical values ​​will be saved on the stack; and when a reference variable is assigned to another reference variable, two identical values ​​will be saved on the stack. Two references to the same heap location are saved in the stack, that is, the address of the same heap is saved in the stack. When performing data operations, for value types, since each variable has its own value, operations on one variable will not affect other variables; for reference type variables, operations on the data of a variable are operations on this variable. When operating on data in the heap, if two reference type variables refer to the same object, the actual meaning is that the heap addresses they save in the stack are the same, so the operation on one variable will affect the other that references the same object. a variable.

Concept:

1. Value type: Data is stored in the stack of memory, and the data can be quickly accessed from the stack. Therefore, the value type represents the actual data.

2. Reference type: Represents a pointer or reference to data stored in the memory heap (including classes, interfaces, arrays and strings).

The value types defined in C# include primitive types (Sbyte, Byte, Short, Ushort, Int, Uint, Long, Ulong, Char, Float, Double, Bool, Decimal), enumeration (enum), and structure (struct)

Reference types include: classes, arrays, interfaces, delegates, strings, etc.

Difference:

The basic difference is how they are stored in memory. Value types only store values ​​in memory, and these value types are stored on the stack. Primitive data types (such as bool and int) belong to this type. The memory unit of the reference type only stores the address of the object in the memory heap, and the object itself is placed in the memory heap. If the value of the referenced value type is null, it means that no object is referenced.

The difference between heap and stack:

Heap and stack are two different concepts, and their storage locations in memory are also different.

The heap is generally used to store variables Length data, such as string type;

The stack is used to store fixed-length data, such as integer type data int (each int variable occupies four bytes). It can be known from the location of data storage that when a value variable is assigned to another value variable, two identical values ​​will be saved on the stack; and when a reference variable is assigned to another reference variable, two identical values ​​will be saved on the stack. Two references to the same heap location are saved in the stack, that is, the address of the same heap is saved in the stack. When performing data operations, for value types, since each variable has its own value, operations on one variable will not affect other variables; for reference type variables, operations on the data of a variable are operations on this variable. When operating on data in the heap, if two reference type variables refer to the same object, the actual meaning is that the heap addresses they save in the stack are the same, so the operation on one variable will affect the other that references the same object. a variable.

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