(Solved)if a variable is already declare as double why should i convert it?

Question

Hello everyone! I just have a question about 1st code project . Why should I convert radius to double if it is already declare as double? does it mean I have to do it for the reason of user input in Console.ReadLine(); ?

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Test
{
internal class Program
{
static void Main(string[] args)
{
const double pi = 3.14;
double radius;

radius = Convert.ToDouble(Console.ReadLine());
double r = radius;

double area = pi * r * r;

Console.WriteLine(area);

}
}
}
edit: Thanks everyone for your help =)

Answer 1

Because ReadLine() will return only strings

Answer 2

Valeriy

Most of the language returns string when you take input.

C#
Python
JavaScript
Ruby
Swift
Kotlin - in case of readLine()

Returns string bydefault

Answer 3

"Because ReadLine() will return only strings"
Alright it makes sense. Thank you.

Answer 4

ReadLine() is a method available in the Console class
By default, it will take everything as a string

The following reasons behind this
======================
In c language we c a problem with real numbers
By default, it will consider every as a double value which is memory wastage
This is happening due to auto-convertion
The same thing happening in CPP

To overcome this from java onwards we are using wrapper classes

In java: Double.parseDouble();
In c# : Convert.toDouble64();
or
double.Parse(Console.ReadLine());

In the above case, it is up to developers whether they need float or double value

Now there is no chance of memory wastage or
lack of memory for variables