Difference between constant and read-only in C# dotnet

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Difference between constant and read-only in C# dot net

Jaimin Shethiya · Answer

Hello Kiran, Please refer below article for more information. Difference Between ReadOnly and Constant in .NET C# Thanks

Sandhiya Priya · Answer

1. Definition Keyword Description const Used to declare compile-time constants (fixed values known at compile time). readonly Used to declare runtime constants (values set at runtime but not changeable afterward). 2. When the Value is Assigned Keyword When Assigned const Must be assigned at declaration. readonly Can be assigned at declaration or in the constructor. Example: public class Demo { public const int ConstValue = 10; // compile-time constant public readonly int ReadOnlyValue; // runtime constant public Demo(int val) { ReadOnlyValue = val; // can be assigned here } } 3. Changeability Keyword Changeable? const Cannot be changed — fixed at compile time. readonly Can be set once per object instance, usually in a constructor. 4. Memory Behavior Keyword Behavior const Acts like a literal — compiler replaces it everywhere it’s used. readonly Stored as a field in memory (part of the object or class). 5. Scope and Usage Keyword Can be used in… const Only with built-in types (int, double, string, etc.) readonly Can be used with reference types, objects, and structs. Example: public static readonly MyClass Obj = new MyClass(); // valid public const MyClass Obj = new MyClass(); // ? invalid 6. Example Comparison public class Example { public const int ConstValue = 100; // fixed at compile-time public readonly int ReadOnlyValue; public Example(int val) { ReadOnlyValue = val; // assigned at runtime } public void Display() { Console.WriteLine(ConstValue); // always 100 Console.WriteLine(ReadOnlyValue); // depends on constructor input } } Usage: Example e1 = new Example(50); Example e2 = new Example(200); e1.Display(); // Const=100, ReadOnly=50 e2.Display(); // Const=100, ReadOnly=200 Summary Table Feature const readonly Value assigned At compile time At runtime Assignment location At declaration only Declaration or constructor Can use with objects No Yes Memory allocation Replaced as literal Stored as field Flexibility Fixed for all Can vary per instance Performance Slightly faster Slightly slower Example Use Case Use const for values that never change , like PI , DaysInWeek , etc. Use readonly for values that depend on runtime input , like a config ID, database connection string, or environment setting.

Rajanikant Hawaldar · Answer

https://www.c-sharpcorner.com/blogs/difference-between-constant-and-readonly

Raja Musab Bin Khalid · Answer

Const are Constants, and its value is assigned at the time of compilation while readonly is runtime variable which is assign on runtime. Both cannot be changed once assigned

Saurabh Prajapati · Answer

Const is a compile-time constant, while readonly is assigned at runtime and cannot be changed afterward.

Difference between constant and read-only in C# dotnet

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