Question

Can somone please tell me what does the syntax below means?

public ScopeCanvas(Context context, IAttributeSet attrs) : base(context, attrs)
{
}

I mean what is method(argument) : base(argument) {} ??

P.S This is a constructor of a class.

Answer 1

The :base syntax is a way for a derived type to chain to a constructor on the base class which accepts the specified argument. If omitted the compiler will silently attempt to bind to a base class constructor which accepts 0 arguments.

class Parent {
  protected Parent(int id) { } 
}

class Child1 : Parent {
  internal Child1() { 
    // Doesn't compile.  Parent doesn't have a parameterless constructor and 
    // hence the implicit :base() won't work
  }
}

class Child2 : Parent {
  internal Child2() : base(42) { 
    // Works great
  }
}

There is also the :this syntax which allows chaining to constructors in the same type with a specified argument list