Partial Class and Partial Methods in CSharp

Partial Class and Partial Methods in C#

Partial classes and partial methods are useful C# features for dividing a class’s implementation into multiple files, which can make it more manageable in large projects. In this article, we’ll explore partial classes and partial methods with code examples.

Partial Classes:

A partial class is a class that can be divided into multiple files, each containing a portion of the class’s implementation. To declare a partial class, use the partial keyword:

// File1.cs
partial class MyClass
{
    public void Method1() { /* Implementation 1 */ }
}

// File2.cs
partial class MyClass
{
    public void Method2() { /* Implementation 2 */ }
}

When the C# compiler processes these files, it combines them into a single class definition, resulting in the MyClass class with both Method1 and Method2.

Partial Methods:

A partial method is a method declared in one part of a partial class and defined in another part. It allows you to provide an optional implementation for a method. Partial methods are typically used for code generation or to allow custom behavior in generated code. To declare a partial method, use the partial keyword:

// File1.cs
partial class MyClass
{
    partial void MyPartialMethod(int x);
}

// File2.cs
partial class MyClass
{
    partial void MyPartialMethod(int x)
    {
        // Actual implementation
    }
}

Partial methods must be declared in one part of the partial class and defined in another part. If they are not defined, they are removed during compilation, resulting in no overhead.

Example:

Here’s an example of a partial class with a partial method:

// File1.cs
partial class Person
{
    partial void LogName();
}

// File2.cs
partial class Person
{
    public string Name { get; set; }

    partial void LogName()
    {
        Console.WriteLine("Name: " + Name);
    }
}

In this example, the LogName method is a partial method that’s declared in one part of the class and defined in another. It’s only invoked if it’s implemented in one of the parts.

Use Cases:

Dividing large classes into multiple files for better code organization.
Implementing code generation tools that need to generate part of a class’s behavior.
Enforcing a consistent interface for generated code while allowing customization in specific parts.

Partial classes and methods in C# are valuable tools for managing and organizing code in large projects and for generating code with customizable hooks for specific behavior.

Stay Connected