C# 类位于单独的文件中 [关闭]

为什么C#类位于单独的文件中？

csharp
// Person.cs
public class Person
{
    public string Name { get; set; }
    public Address Address { get; set; }
}
// Address.cs
public class Address
{
    public string City { get; set; }
    public string Street { get; set; }
}

csharp
// Calculator.cs
public class Calculator
{
    public int Add(int a, int b)
    {
        return a + b;
    }
    public int Subtract(int a, int b)
    {
        return a - b;
    }
    public int Multiply(int a, int b)
    {
        return a * b;
    }
    public int Divide(int a, int b)
    {
        if (b == 0)
        {
            throw new DivideByZeroException("Cannot divide by zero.");
        }
        return a / b;
    }
}