Introduction

In this article, we will learn about how to use partial class in C#. A partial class is an important class in C# This provides a special ability to implement the functionality of a single class into multiple files, and all these files are combined into a single class file in C#
When the application is compiled, all of these files are integrated into a single class file, giving it the unique ability to implement the functionality of a single class into several files. Using the partial keyword produces a partial class. This keyword can be used to divide a method, interface, or structure's functionality into different files. 

public partial Clas_name  
{
        // code
}

important topic

  • Use the partial keyword, and all required files must be present at compilation time in order to create the final file when you want to split the functionality of a class, method, interface, or structure over multiple files.
  • Only immediately before terms like struct, class, and interface can the partial modifier appear.
  • You can use a different source file name, but each component of the partial class definition should be in the same assembly and namespace.
  • Every element of the partially defined class should be equally accessible to everyone as private, protected, etc.
  • The entire class is declared to be of the same type if any portion of the partial class is declared as an abstract, sealed, or base.

Example

Here, you can say a class named Country and split the definition of Country class into two different files named Country.cs, and Country1.cs as shown below 

 public partial class Country
    {
        private string Country_Name ;
        private int TotalNumberofCountry ;

        public Country(string a, int t)
        {
            this.Country_Name = a;
            this.TotalNumberofCountry = t;
        }
    }

When we run the aforementioned code, the compiler merges Class1.cs and Class2.cs into one file, referred to as Country, as illustrated in the example below.
CountryThe Main Method might be present in this class. Here, the Main() method is omitted for simplicity's sake. 

 internal class Class1
    {
    }
        // readonly variables
        // Readonly structure
        public class Class2
        {
            private string Country_Name;
            private int CountryCity ;

            public Class2 (string a, int t)
            {
                this.Country_Name = a;
                this.CountryCity = t;
            }

            public void Display()
            {
                Console.WriteLine("Author's name is : " + Country_Name);
                Console.WriteLine("Total number articles is : " + CountryCity);
            }
        }

    }

Advantages

With the statement of partial classes, multiple developers can work simultaneously in the same class in different files.
With the statement of a partial class concept, you can split the UI of the design code and the business logic code to read and understand the code.
when we were working with automatically generated code, the code can be added to the class without having to recreate the source file like in Visual studio.
We can also maintain your application in an efficient manner by compressing large classes into small ones.

Conclusion

This code example taught us Partial Class in C#

FAQs

Q- Can a partial class be defined across multiple namespaces?

A- No, a partial class must be defined within the same namespace. It cannot be split across multiple namespaces.

Q- How many partial classes can you have for a single class?

A- You can have multiple partial classes for a single class, each defined in a separate file. However, all the partial classes must be defined within the same namespace.

Q- Can a partial class have different access modifiers?

A- Yes, a partial class can have different access modifiers for its individual parts. For example, one part can be declared as public, while another part can be declared as private. However, the combined class will have the most restrictive access modifier among its parts.

Q- How are partial methods related to partial classes?

A- Partial methods are methods that are defined in one part of a partial class but implemented in another part. The declaration and implementation of a partial method are split between two partial class files. The implementation part is optional and can be omitted if not needed.

Q- Can partial methods be public?

A- No, partial methods can only have the private access modifier. They are implicitly private and cannot be explicitly declared as public, protected, or internal.

Q- What are some use cases for partial classes in C#?

A- Partial classes are commonly used in scenarios such as code generation, code separation in large projects, and separating auto-generated code from manually written code. They provide a way to extend or modify generated classes without altering the generated code itself.

Q- Can you inherit from a partial class?

A- Yes, you can inherit from a partial class just like any other class. Inheritance is not affected by the fact that the class is defined as a partial class.

Q- Can you combine partial classes defined in different assemblies?

A- No, partial classes must be defined within the same assembly to be combined. The compiler needs access to all parts of the partial class during compilation.

Q- Is there any limitation on the order in which the parts of a partial class are defined?

A- No, there is no specific order requirement for defining the parts of a partial class. They can be defined in any order and still be compiled as a single class at runtime.