20. Partial Class

A partial class in C# allows a single class to be divided into multiple files, enabling developers to organize and maintain large code bases more effectively. Must have partial keyword (no class name like public class MyClass supported).

public partial class MyClass
{
    public void Print1()
    {
        Console.WriteLine("Print 1");
    }
}
 
public partial class MyClass
{
    public void Print2()
    {
        Console.WriteLine("Print 2");
    }
}
 
public class Program
{
    static void Main(string[] args)
    {
        var myClass = new MyClass();
        myClass.Print1();
        myClass.Print2();
    }
}

Advantages of Partial Classes:

1. Split UI design and business logic easily.
2. No need to regenerate source files for auto-generated files.
3. Facilitates concurrent development by multiple developers.
4. Easier maintenance and development of large classes by breaking them into smaller, manageable partial classes.