C# Positional Parameters, Named Parameters and Default Values Explained

In C#, methods can accept arguments in multiple flexible ways using positional parameters, named parameters, and default parameter values. Understanding these features helps developers write more readable code and avoid confusion when calling functions. In this guide, we will break down each concept with examples and clear explanations.

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1. Positional Parameters with Default Values

In positional parameters, the values are passed based on their order in the method call. C# allows you to assign default values to parameters, so callers do not need to provide all arguments.

public static void DisplayInfo(string name, int age = 30, string city = "Unknown")
{
    Console.WriteLine($"Name: {name}, Age: {age}, City: {city}");
}

How the method call works:

• DisplayInfo("Alice", 25, "New York"); — All parameters supplied
• DisplayInfo("Bob"); — Age and city use default values
• DisplayInfo("Charlie", city: "Los Angeles"); — Mixing positional and named

2. Named Parameters in C#

Named parameters allow you to specify which argument corresponds to which parameter by using the parameter name.

public static void DisplayDetails(string name, int age, string city)
{
    Console.WriteLine($"Name: {name}, Age: {age}, City: {city}");
}

Example call:

DisplayDetails(city: "Paris", age: 28, name: "Diana");

This improves readability and allows arguments to be passed in any order.

3. Combining Positional and Named Parameters

C# allows mixing positional and named parameters, but positional arguments must always come first.

public static void SetEmployeeInfo(string name, int age, string position = "Developer", string department = "IT")
{
    Console.WriteLine($"Name: {name}, Age: {age}, Position: {position}, Department: {department}");
}

Example calls:

• Positional + named: SetEmployeeInfo("Eve", 35, position: "Manager", department: "HR");
• Defaults used: SetEmployeeInfo("John", 28);

4. Methods Where All Parameters Have Default Values

You can assign default values to every parameter, making all of them optional.

public static void PrintProductInfo(string product = "Unknown", int quantity = 1, double price = 10.0)
{
    Console.WriteLine($"Product: {product}, Quantity: {quantity}, Price: ${price}");
}

Function calls:

• PrintProductInfo(); — All defaults used
• PrintProductInfo("Laptop", quantity: 2);
• PrintProductInfo("Phone", 5, 299.99);

Summary

• Positional parameters — order matters
• Named parameters — order does not matter
• Default values — make parameters optional

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