There are two ways to do the above :

1. Use this keyword to acheive this . Example below :

 public class Employee
{
    public Employee(): this(10)
    {
        // This is the no parameter constructor method.
        // First Constructor
    }

    public Employee(int Age)
    {
        // This is the constructor with one parameter.
        // Second Constructor
    }
}

So first constructor will can second constructior using this keyword

2.

public class Employee
{
    public Employee()
    {
        Employee(10)
        // This is the no parameter constructor method.
        // First Constructor
    }

    public Employee(int Age)
    {
        // This is the constructor with one parameter.
        // Second Constructor
    }
}