Base class' constructor takes effect even not explicitly called.

I almost have no impression at all on a heavily important c# grammar issue......

Originally I thought base class' constructor doesn't participate in any of derived class' constructional logic unless explicitly called for serving , just like :

 
public Manager(int initialdata) : base()
{
    //Add further instructions here. 
}
 

In this manner the default constructor is to be called undoubtedly. However in my bad conception I think code like this:

 
public Manager(int initialdata)
{
    //Add further instructions here. 
}
 

doesn't call the base class' default constructor because there is no explicit code ":base()" coming after main class name "Manager" so the base default constructor has no impact here.

However I am wrong. The two pieces above are semantically identical. Official tutorial tells me:

In a derived class, if a base-class constructor is not called explicitly using the base keyword, then the default constructor, if there is one, is called implicitly.

Here is official link stating this case:

Using Constructors (C# Programming Guide)