What is the difference between const and read-only in C#?

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Aryan Kumar · Answer

The const and readonly keywords in C# are both used to declare constants. However, there are some key differences between the two keywords. const constants are compile-time constants, while readonly constants are runtime constants. This means that the value of a const constant is known at compile time, while the value of a readonly constant can be changed at runtime.const constants must be initialized when they are declared, while readonly constants can be initialized later. This means that you cannot declare a const constant without initializing it, while you can declare a readonly constant and initialize it later.const constants are implicitly static, while readonly constants can be static or non-static. This means that a const constant is always a static member of a class, while a readonly constant can be a static member or an instance member of a class. In general, you should use const constants when the value of the constant is known at compile time and you do not need to be able to change the value at runtime. You should use readonly constants when the value of the constant can be changed at runtime, or when you need to be able to declare a constant that is not a static member of a class. Here is a table that summarizes the key differences between const and readonly: Feature const readonly Compile-time constant Yes No Initialization Must be initialized when declared Can be initialized later Static Implicitly static Can be static or non-static When to use When the value of the constant is known at compile time and you do not need to be able to change the value at runtime When the value of the constant can be changed at runtime, or when you need to be able to declare a constant that is not a static member of a class

Feature	`const`	`readonly`
Compile-time constant	Yes	No
Initialization	Must be initialized when declared	Can be initialized later
Static	Implicitly static	Can be static or non-static
When to use	When the value of the constant is known at compile time and you do not need to be able to change the value at runtime	When the value of the constant can be changed at runtime, or when you need to be able to declare a constant that is not a static member of a class

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What is the difference between const and read-only in C#?

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