readonly vs const csharp
Code Example - readonly vs const csharp
readonly keyword is used to define a variable
which can be assigned once after declaration
either during declaration or in constructor.
const keyword is used to define a constant to be used in the program.
csharp const vs readonly
A const is a compile-time constant whereas readonly allows a value to be calculated at run-time and set in the constructor or field initializer. So, a 'const' is always constant but 'readonly' is read-only once it is assigned.
Eric Lippert of the C# team has more information on different types of immutability.