Area of a Circle in Basic Concepts C#

Question

Guys,
Can someone help me to get through the last elements in a C# course?
I wanted to start doing the programming parts at the end of each segment but the first one already blocks me out. There are 3 first steps do do but nothing gets me throught all of them, then to unlock 4 and 5, so maybe I can get it validated and move forward.

declaring 5, the area of a circle gives you 78,5, ok done, step 2, I add the next part of code, r=6.4, area = whatever... what is wrong with this thing or what is wrong with me? :)
Any hints how to pass it through please?
Here is my code:

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

namespace SoloLearn
{
class Program
{
static void Main(string[] args)
{
const double pi = 3.14;
double radius1, radius2, radius3;

int r1 = 5;
radius1 = Convert.ToDouble(pi * r1 * r1);
Console.WriteLine(radius1);

double r2 = 6.4;
radius2 = Convert.ToDouble(pi * r2 * r2);
Console.WriteLine(radius2);

int r3 = 10;
radius3 = Convert.ToDouble(pi * r3 * r3);
Console.WriteLine(radius3);

}
}
}

Answer 1

You need to declare one variable as an input instead of many variables.
radius = Convert.ToDouble(Console.ReadLine());

Answer 2

Because it's not necessary to add extra prompt messages in your solutions.
Also, inputs are tested by compiler itself. You can check them in test cases :)

Answer 3

Thank you Simba,
It works in VS but not inside the Sololearn code window, actually I don’t even get to input my value...

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

namespace Egzamin_1s
{
class Program
{
static void Main(string[] args)
{
const double pi = 3.14;
double radius;

Console.WriteLine("What's your input?");
radius = Convert.ToDouble(Console.ReadLine());

Console.WriteLine(pi * radius * radius);

}
}
}

Answer 4

Well, ok I got it through when I changed the input line to comments:

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

namespace SoloLearn
{
class Program
{
static void Main()
{
const double pi = 3.14;
double radius;

//Console.WriteLine("What's your input?");
radius = Convert.ToDouble(Console.ReadLine());

Console.WriteLine(Convert.ToDouble(pi * radius * radius));

}
}
}

This is so weird !

Answer 5

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

namespace Egzamin_1s
{
class Program
{
static void Main(string[] args)
{
const double pi = 3.14;
double radius=double.Parse(Console.ReadLine());
Console.WriteLine(pi * radius * radius);

}
}
}