How to call default contstructor from another one

One of my team mate asked me this question today. I was not aware of this before that.
Here is a code for the same,

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public class A { public A() { Console.WriteLine("Default"); } public A(string msg) : this() { Console.WriteLine("this is param : " + msg); } }

Now when you create instance of class A as,

1	A objA = new A("Hello");

It will print statements as;
Default
this is param : Hello