Const
Constant fields are the fields that cannot be modified. At the time of declaration, you need to assign a value to it.
const int a = 5;
Readonly
A Read-only field is initialized at the time of declaration or you can also set it within the constructor.
Let us see an example in which the read-only field is initialized inside the constructor −
Example
class Calculate {
readonly int z;
public Demo( ) {
z = 20;
}
}