how to rewrite the following code so that i don't have to assign readonly variable in a method only called by constructor?

e.g

        Class A
          {
           readonly Bclass B;
           readonly Cclass C;
           public void Class()
               {开发者_JAVA百科
                 Action1();
                 Action2();
                 Action3();
               }
           void Action2()
              {
                Dosomething1();
                B=Dosomething2(); //There goes the problem.
                C=Dosomething3();
                Dosomething4();
              }
           ...
          }

BTW, i know i can put all the Dosomthing() into the constructor, but the code hence becomes less readable.

You could refactor A so that B is exposed as a property with only a setter:

public class A
{

    public A() 
    {
        _b = DoSomething();
    }

    private BClass MyClassB
    {
        get { return _b; }
    }

    private BClass _b;
}

There are a couple of other things you could potentially do, but it is hard to see exactly what your problem is with using a readonly instance of B. It will be done this way to make it immutable - once it has been set in the constructor it cannot be changed anywhere else in the class - note that you lose the immutability if you use the property i illustrated above.

    Class A
      {
       readonly Bclass B;
       readonly Cclass C;

       public void Class()
           {
             Action1();
             Tuple<B,C> init = Action2();
             B = init.B;
             C = init.C;
             Action3();
           }
      }

Unfortunately, C# lacks tuple support, so you cannot write

B, C = Action2();