newbie need your help

1. I have an c# solution file (x.sln) called TestCallFunction
2. in this x.sln i have to folders called Calculate and Take
3. in the Calculate folder i have a file called Execute which has a class called Cal. (this class is to to the calculation)
ie.
 using System;
using TakeX;
using TakeY;
namespace Calculate
{
Class Cal
{
static int Main()
{console.WriteLine("x + y is " + (XValue.XNum() + YValue.YNum()));
return 0;
}
}
}
 
4. in the Take folder i have two files which called TakeX and TakeY, respectively;
ie. (in the TakeX i have-- similar to TakeY)
using system;
namespace TakeX
{
class XValue
{
public static int XNum()
{
return 100;
}
}
}
now, this small program works fine.
but, because no ...