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Partial Methods in C Sharp

Partial Methods in C Sharp

13 Mar 2024
3 min read
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Partial Methods: An Overview

A partial method is a special method that exists within a partial class or structure. One part of the partial class or struct has only partial method declaration means signature and another part of the same partial class or struct may have implementation for that partial method. If the implementation is not provided for the declared partial method, the method and all calls to that partial method will be removed at compile time. However, in this C# Tutorial, we will explore more about Partial Methods which will include, partial methods in c# with its example, the need of partial methods, the requirement of partial methods in c#, and, also when partial methods are used in C#.

Why are partial methods required?

Partial methods are particularly helpful for customizing auto-generated code by the tool. Whenever the tool generates the code then the tool may declare some partial method and implementation of these methods is decided by the developers.

If you are using an entity framework for making DAL then you have seen that Visual Studio makes a partial method OnContextCreated() as shown below. Now the implementation of it depends on you whether you want to use it or not.


Let's elaborate partial method in C# Compiler with its example:

 public partial class DALEntities : ObjectContext
 #region Constructors
 // Constructors for DALentities
#region Partial Methods 
partial void OnContextCreated(); 
 // This part can be put in the separate file
public partial class DALEntities : ObjectContext
 partial void OnContextCreated()
 // put method implementation code 
 Debug.WriteLine("OnContextCreated partial method"); 

Read More - C Sharp Interview Questions

Key points about the partial method

  1. Partial methods can be declared or defined within the partial class or struct.

  2. Partial methods are implicitly private and declarations must have partial keywords.

  3. Partial methods must return void.

  4. Partial methods implementation is optional.

  5. Partial methods can be static unsafe and generic.

  6. Partial methods can have ref parameters but not out parameters since these can't return value.

  7. You can also make delegate to a partial method that has been defined and implemented. If the partial method is only defined, you can not.

  8. The signatures of the partial method will be the same in both parts of the partial class or struct.

partial class Example 
partial void ExampleMethod(string s); 
 // This part can be put in the separate file 
partial class Example { //Implement the method 
partial void ExampleMethod(String s)
 Console.WriteLine("Your string: {0}", s);

I hope you will enjoy these tricks while programming C#. I would like to have feedback from my blog readers. Your valuable feedback, questions, or comments about this article are always welcome. Also, Consider our C# Programming Course for a better understanding of all C# concepts.


Q1. What is a partial class in C#?

It is a feature that allows developers to split the definition of a class or a struct, an interface, or a method over two or more source files.

Q2. What is the return type of partial method in C#?

void or anon-awaitable async void, which limits their usefulness.

Q3. What are partial types and partial methods?

Partial types can also declare partial Methods, which can be used to advertise the availability of a method in one part, and optionally provide an implementation on the other part. 

Q4. Why do we need partial in C#?

In this, Rather than cluttering a single file with thousands of lines of code, you separate them into different files based on functionality, 

Q5. Can we create partial method in C#?

Yes. it must be declared first(like an abstract method), with a signature only and no definition. 

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About Author
Shailendra Chauhan (Microsoft MVP, Founder & CEO at Scholarhat by DotNetTricks)

Shailendra Chauhan is the Founder and CEO at ScholarHat by DotNetTricks which is a brand when it comes to e-Learning. He provides training and consultation over an array of technologies like Cloud, .NET, Angular, React, Node, Microservices, Containers and Mobile Apps development. He has been awarded Microsoft MVP 8th time in a row (2016-2023). He has changed many lives with his writings and unique training programs. He has a number of most sought-after books to his name which has helped job aspirants in cracking tough interviews with ease.
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