Difference between Method and Function in C#

In C#, the terms method and function are often used interchangeably, but there is a subtle distinction. A method is a function that belongs to a class or struct, while a function is a more general term for a reusable block of code that performs a specific task.

Every C# program has at least one class with a method named Main. Methods are defined within classes and operate on the data and behavior of those classes.

Syntax

Following is the syntax for defining a method in C# −

[access modifier] [return type] MethodName(parameters) {
   // method body
   return value; // if return type is not void
}

Key Terminology

Using Methods in Classes

Methods encapsulate functionality within classes and can access class members. Here's a complete example −

using System;

class NumberManipulator {
   public int FindMax(int num1, int num2) {
      /* local variable declaration */
      int result;
      if (num1 > num2) {
         result = num1;
      } else {
         result = num2;
      }
      return result;
   }

   public void DisplayResult(int max) {
      Console.WriteLine("The maximum value is: " + max);
   }
}

class Program {
   public static void Main() {
      NumberManipulator nm = new NumberManipulator();
      int result = nm.FindMax(15, 25);
      nm.DisplayResult(result);
      
      // Direct method call
      int anotherResult = nm.FindMax(100, 200);
      nm.DisplayResult(anotherResult);
   }
}

The output of the above code is −

The maximum value is: 25
The maximum value is: 200

Static Methods vs Instance Methods

Methods can be either static (belong to the class) or instance methods (belong to object instances) −

using System;

class MathOperations {
   // Static method - belongs to the class
   public static int Add(int a, int b) {
      return a + b;
   }

   // Instance method - belongs to object
   public int Multiply(int a, int b) {
      return a * b;
   }
}

class Program {
   public static void Main() {
      // Static method call - no object needed
      int sum = MathOperations.Add(10, 20);
      Console.WriteLine("Sum: " + sum);

      // Instance method call - object required
      MathOperations math = new MathOperations();
      int product = math.Multiply(5, 6);
      Console.WriteLine("Product: " + product);
   }
}

The output of the above code is −

Sum: 30
Product: 30

Method Overloading

C# supports method overloading, allowing multiple methods with the same name but different parameters −

using System;

class Calculator {
   public int Add(int a, int b) {
      return a + b;
   }

   public double Add(double a, double b) {
      return a + b;
   }

   public int Add(int a, int b, int c) {
      return a + b + c;
   }
}

class Program {
   public static void Main() {
      Calculator calc = new Calculator();
      
      Console.WriteLine("Integer addition: " + calc.Add(5, 10));
      Console.WriteLine("Double addition: " + calc.Add(3.5, 2.1));
      Console.WriteLine("Three numbers: " + calc.Add(1, 2, 3));
   }
}

The output of the above code is −

Integer addition: 15
Double addition: 5.6
Three numbers: 6

Conclusion

In C#, methods and functions refer to the same concept - reusable blocks of code that perform specific tasks. The term "method" is preferred in C# since these functions always belong to classes or structs. Methods can be static or instance-based and support features like overloading for enhanced functionality.