C# Methods Explained: Declaration, Calling, Parameters, Return Types & More

C# Methods Explained

Master the fundamentals of C# methods—how to declare them, invoke them, handle parameters, return values, and leverage built‑in functionality—with clear examples.

A method is a reusable block of code that performs a specific task. For instance, if you’re building a drawing program that needs to create and color a circle, you could split the work into two distinct methods: one to draw the circle and another to color it. This modular approach improves readability, testability, and reusability.

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Declaring a Method in C#

The basic syntax for defining a method in C# is:

returnType methodName() {
  // method body
}

Components:

• returnType – Specifies the data type returned by the method. If no value is returned, use void.
• methodName – An identifier used to reference the method.
• method body – The statements that execute when the method runs, enclosed in braces.

Example:

void display() {
  // code
}

Here, display() is the method name and void indicates it does not return a value.

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Calling a Method in C#

Once declared, you invoke a method by its name followed by parentheses. For the display() example:

// call the method
display();

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Practical Example: Using a Method

using System;

namespace MethodDemo {
  class Program {
    // Method declaration
    public void Display() {
      Console.WriteLine("Hello World");
    }

    static void Main(string[] args) {
      // Create an instance of Program
      Program p1 = new Program();

      // Invoke the Display method
      p1.Display();

      Console.ReadLine();
    }
  }
}

Output

Hello World

This demonstrates creating an object p1 of the Program class and calling its Display() method.

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Method Return Types

Methods can return data or be void. When a return value is required, the return statement sends the value back to the caller, and the method’s return type must match the value’s type.

int AddNumbers() {
  int sum = 5 + 14;
  return sum;
}

Example: Returning an Integer

using System;

namespace MethodDemo {
  class Program {
    // Static method with return type
    static int AddNumbers() {
      int sum = 5 + 14;
      return sum;
    }

    static void Main(string[] args) {
      int sum = AddNumbers();
      Console.WriteLine(sum);
      Console.ReadLine();
    }
  }
}

Output

19

Note that static methods belong to the class itself, so no instance is required to call them.

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Methods with Parameters

Parameters allow methods to accept input values. They are declared in the method signature and passed during invocation.

int AddNumber(int a, int b) {
  return a + b;
}

Calling the method with arguments:

AddNumber(100, 100);

Example 1: Adding Two Numbers

using System;

namespace MethodDemo {
  class Program {
    int AddNumber(int a, int b) {
      return a + b;
    }

    static void Main(string[] args) {
      Program p1 = new Program();
      int sum = p1.AddNumber(100, 100);
      Console.WriteLine("Sum: " + sum);
      Console.ReadLine();
    }
  }
}

Output

Sum: 200

Example 2: Single Parameter Method

using System;

namespace MethodDemo {
  class Program {
    string Work(string task) {
      return task;
    }

    static void Main(string[] args) {
      Program p1 = new Program();
      string result = p1.Work("Cleaning");
      Console.WriteLine("Work: " + result);
      Console.ReadLine();
    }
  }
}

Output

Work: Cleaning

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Built‑In Methods

Beyond user‑defined methods, C# offers a rich library of built‑in methods. For example:

• Math.Sqrt() – Calculates the square root.
• string.ToUpper() – Converts a string to uppercase.

Example: Using Math.Sqrt

using System;

namespace MethodDemo {
  class Program {
    static void Main(string[] args) {
      double result = Math.Sqrt(9);
      Console.WriteLine("Square root of 9: " + result);
    }
  }
}

Output

Square root of 9: 3

Here, Math.Sqrt is part of the System.Math class in .NET, documented by Microsoft.

Learn more about C# built‑in methods.

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Method Overloading

C# allows multiple methods with the same name, provided their parameter lists differ. This is called method overloading.

using System;

namespace MethodOverloadDemo {
  class Program {
    // One-parameter overload
    void Display(int a) {
      Console.WriteLine("Arguments: " + a);
    }

    // Two-parameter overload
    void Display(int a, int b) {
      Console.WriteLine("Arguments: " + a + " and " + b);
    }

    static void Main(string[] args) {
      Program p1 = new Program();
      p1.Display(100);
      p1.Display(100, 200);
      Console.ReadLine();
    }
  }
}

Output

Arguments: 100
Arguments: 100 and 200

Overloading enhances readability and flexibility. For deeper insights, see C# Method Overloading.

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