The C# Partial Class: Splitting a Class in C# with the Partial Method

c# partial classC#, or C Sharp was built to be used with the .NET Microsoft framework. C Sharp is mainly used for developing applications for Windows, for web development and for networking. C# is a fully object oriented language – it supports polymorphism, data abstraction, data encapsulation and inheritance. The character “#” comes from the musical key “sharp”, which corresponds to an increase in the pitch in music. Similarly, the language C# was designed to address the shortcomings of C and C++ and provide an improved, updated language to the programmer. C# has an improved garbage collector which the available memory automatically, without the developer having to worry about it. C# also is much more stable than C and C++, and you don’t have to type as much code to perform programming tasks. C# is also a platform-independent language, in the mold of Java. This means that you can run a C# program on any machine, regardless of the architecture present (as long as the .NET framework has been installed). Learn more about how C# works with the .NET framework with this course.

We’re going to take a look at the C# partial class in this tutorial. You need to be familiar with the basics of the language (the structure and syntax of the program) to understand the tutorial. Microsoft and other developers have invested a lot of effort into it. Chances are, it will become one of the most popular programming languages in the future. It’s definitely worth your while to learn it. You can sign up for our simple, easy-to-understand C# course for complete beginners. We’ll teach you everything you need to know about the language- you’ll be writing your own programs in no time. You’ll find it easier to learn the language if you have some knowledge of C, C++ and Java. Those pressed for time, can instead take this primer to learn C# in just 1 hour.

What is a C# Partial Class?

A partial class is a class that has been separated into parts. If you use the partial keyword when you’re declaring a class, your class may be split into separate files. You can provide separate methods for the different parts of your class.

Why do you need a partial class? In C#, a single project cannot have two separate classes. But sometimes you do need two classes for it – if the code is bloating the class, for example. In this case, you can use the partial modifier to divide the class. In applications that use partial classes, you will find that one of the partial classes contains code that has to be edited frequently while the other partial class will be rarely edited or contain machine-generated code that isn’t understandable to the user. Sometimes several developers need to work on a single project. In this case, it’s easier to make several partial classes with separate code. This code is then gathered together during runtime and executed as a single unit.

Example of a C# Partial Class

Let’s write a simple program that demonstrates the concept of a C# partial class.

class Employee
{
static void Main()
{
E.E1();
E.E2();
}
}
//part 1 of the partial class
using System;
partial class E
{
public static void E1()
{
Console.WriteLine("This is Employee Number 1");
}
}
//part 2 of the partial class
using System;
partial class E
{
public static void E2()
{
Console.WriteLine("This is Employee Number 2");
}
}
Output: This is Employee Number 1
This is Employee Number 2

 

First, we created a class called Employee. In the main method of the program, we declared two files, which were a part of E: E1 and E2. E can then be declared as a partial class. In the 1st part of the partial class declaration, we printed “This is Employee Number 1” to the screen using the Console.WriteLine method. In the 2nd part of the partial class declaration, we printed “This is Employee Number 2” using the same method. Simply put, all we’ve done is divide a single class into two separate files. The 1st file will be saved as E1.cs, while the 2nd file will be saved as E2.cs in the system. The “partial” keyword must be included in the declaration, of course. You will encounter an error without it. The name of every section of a class that you make partial has to be the same (during declaration). The name of the source file for every section of the partial class, however, can be different. Also, it’s required that you keep all parts of the partial class in the same namespace.

For additional resources on this topic, you can check out the official Microsoft documentation. Alternatively, you can just sign up for our C# sharp course – we cover all the aspects of C# in 10 easy steps.

Keep in mind that partial classes have the same accessibility – if you declare one of them public, all of them must be public. Also, if a partial class inherits an interface, all of the other partial classes inherit it too.

During Compile Time

What happens to the partial classes at compile time? The partial classes will be merged into a single class. The files E1.cs and E2.cs will be merged into a single file for class E. The methods found in class E1 and class E2 will be merged into a single code block, while the two partial classes will be merged into class E. It will look like this:

internal class E
{
public static void E1()
{
Console.WriteLine(“This is Employee Number 1”);
}
public static void E2()
{
Console.WriteLine(“This is Employee Number 2”);
}
}

As you can see, the two classes have been merged into a single internal class E. The methods of those two classes are also placed inside the same class and are executed simultaneously.

Benefits of Using a Partial Class

So what are the benefits of using a partial class? Let’s take a look at some of them:

  • Several developers can work on a project simultaneously if they work with partial classes. This is, perhaps, the biggest benefit of using a partial class. Large projects that require many developers can be finished faster and with less effort because of this.
  • Large, bloated classes can be made smaller by making them partial. This allows you to make a program that is easier to understand and maintain. It also allows you to divide code into understandable sections, or separate machine level code from normal code, or to separate code that you regularly edit with code you don’t edit at all. For example, when Windows Forms programs are created in Visual Studio, the machine generated code is categorized separately from the normal code.
  • It’s easier to categorize code with partial classes. You can separate business logic from design logic, for example- which is often done in Visual Studio. Developers with experience in different aspects and applications of C# sharp can work on separate parts of the same project because of this.
  • Another major advantage of partial classes is that it’s easier to add new code without editing the original source file. Just declare a new partial class and you’re done.

Learning to use partial classes will help you develop efficient and easy to maintain applications. Once you’re comfortable with the basics, you can even learn how to build Android applications using C# with this special course!