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Partial Classes and Methods

Explore how to use partial classes and partial methods in C# to split class definitions and method implementations across different files. Understand their uses, restrictions, and benefits for collaborative development and code generation scenarios.

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Partial classes

There is a C# feature that allows us to split class definition into multiple locations or files. Using the partial keyword, we inform the compiler that the class source code is located in multiple places:

C#
using System;
namespace PartialClasses
{
    class Program
    {
        static void Main(string[] args)
        {
            // Despite the class definition is contained in separate files,
            // it is one class
            var person = new Person()
            {
                FirstName = "John",
                LastName = "Doe",
                Age = 34,
                Occupation = "Software Developer",
                AnnualSalary = 120000m
            };
            person.PrintFullName();
        }
    }
}

Partial classes are a C# compiler feature. Partial class definitions are assembled together before they’re compiled to IL code:

public partial class C 
{
    public void M() 
    {
    }
}

public partial class C 
{
    public void K() 
    {
    }
}

The code above compiles ...