Value Type and Reference Types

typesinnetThe Types in .NET Framework are either treated by Value Type or by Reference Type. A Value Type holds the data within its own memory allocation and a Reference Type contains a pointer to another memory location that holds the real data. Reference Type variables are stored in the heap while Value Type variables are stored in the stack.

Value Types

value_typeA Value Type stores its contents in memory allocated on the stack. When you created a Value Type, a single space in memory is allocated to store the value and that variable directly holds a value. If you assign it to another variable, the value is copied directly and both variables work independently. Predefined datatypes, structures, enums are also value types, and work in the same way. Value types can be created at compile time and Stored in stack memory, because of this, Garbage collector can’t access the stack.

Examples : int, enum, structs.  

Reference Types

reference_type1Reference Types are used by a reference which holds a reference (address) to the object but not the object itself. Because reference types represent the address of the variable rather than the data itself, assigning a reference variable to another doesn’t copy the data. Instead it creates a second copy of the reference, which refers to the same location of the heap as the original value. Reference Type variables are stored in a different area of memory called the heap. This means that when a reference type variable is no longer used, it can be marked for garbage collection. Examples of reference types are Classes, Objects, Arrays, Indexers, Interfaces etc.

Examples : class, interface, delegate, string, object, Array

Value Type Reference Type
They are stored on stack They are stored on heap
Contains actual value Contains reference to a value
Cannot contain null values. However this can be achieved by nullable types Can contain null values.
Value type is popped on its own from stack when they go out of scope. Required garbage collector to free memory.
Memory is allocated at compile time Memory is allocated at run time

Stack And Heap

Stack Heap
Values are stored on one another like a stack. Values are stored in random dumped into a huge space
Used for value type Used for reference types

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