Assigning a value to an inherited readonly field?

Question

So I have a base class that has many children. This base class defines some readonly properties and variables that have default values. These can be different, depending on the child.

Readonly properties/fields allow you to change the value of the variable inside the constructor and also the definition, but nowhere else. I get a 'readonly variable can only be assigned to in a constructor' error if I try to change the value of an inherited readonly variable in the child class' constructor. Why is this and how can I work around this, without Reflection?

My intention: To allow user extensibility through scripts where they can only change certain fields once.

Answer 1

The reason is that you can only assign to readonly fields in the constructor of that class.
According to the definition of readonly in the C# Reference (emphasis mine):

When a field declaration includes a readonly modifier, assignments to the fields introduced by the declaration can only occur as part of the declaration or in a constructor in the same class.

To work around this, you could make a protected constructor in the base that takes a parameter for the readonly property.

An example:

using System; using System.Collections.Generic; using System.Linq; using System.Text;  namespace ConsoleApplication1 {     class Program     {         static void Main(string[] args)         {             Base b = new Child();             Console.WriteLine(b.i);             Console.Read();         }     }      class Base     {         public readonly int i;          public Base()         {             i = 42;         }          protected Base(int newI)         {             i = newI;         }     }      class Child : Base     {         public Child()             : base(43)         {}     } }