Params keyword for variable arguments in C Sharp (C#) - Step-by-Step Execution

Concept Flow - Params keyword for variable arguments

Call method with params

↓

Params array created

↓

Method receives array

↓

Loop through array elements

↓

Process each argument

↓

Method ends

The params keyword lets a method accept any number of arguments as an array, which the method then processes one by one.

Execution Sample

C Sharp (C#)

void PrintNumbers(params int[] numbers)
{
    foreach (int num in numbers)
        Console.WriteLine(num);
}

PrintNumbers(1, 2, 3);

This method prints each number passed to it using the params keyword.

Execution Table

Step	Action	Params Array Content	Loop Variable (num)	Output
1	Call PrintNumbers(1, 2, 3)	[1, 2, 3]	N/A	N/A
2	Enter foreach loop, num = first element	[1, 2, 3]	1	Print 1
3	Next iteration, num = second element	[1, 2, 3]	2	Print 2
4	Next iteration, num = third element	[1, 2, 3]	3	Print 3
5	End of array reached, exit loop	[1, 2, 3]	N/A	Loop ends

💡 All elements in the params array processed, loop ends.

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	Final
numbers	N/A	[1, 2, 3]	[1, 2, 3]	[1, 2, 3]	[1, 2, 3]
num	N/A	1	2	3	N/A

Key Moments - 2 Insights

Why does the method receive an array even though we pass separate numbers?

Because the params keyword collects all arguments into a single array, as shown in the execution_table step 1 where the array [1, 2, 3] is created.

What happens if no arguments are passed to the method?

The params array is empty, so the foreach loop does not run. This is implied by the loop ending immediately if the array length is zero.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of 'num' at step 3?

A 2

B 3

C 1

D N/A

💡 Hint

Check the 'Loop Variable (num)' column at step 3 in the execution_table.

At which step does the foreach loop end?

A Step 3

B Step 4

C Step 5

D Step 2

💡 Hint

Look for the row where the output says 'Loop ends' in the execution_table.

If we call PrintNumbers() with no arguments, what changes in the execution_table?

A The params array contains one element with value 0

B The params array is empty and the loop does not run

C The method throws an error

D The loop runs once with num = null

💡 Hint

Recall the key_moments explanation about empty params arrays and loop behavior.

Concept Snapshot

Use 'params' before the last parameter to accept variable arguments.
The method receives these as an array.
You can pass zero or more arguments.
Inside the method, treat the parameter as an array.
Example: void M(params int[] nums) { foreach(var n in nums) ... }

Full Transcript

The params keyword in C# allows a method to accept any number of arguments as an array. When you call a method with params, the compiler creates an array from the arguments and passes it to the method. Inside the method, you can loop through this array to process each argument. If no arguments are passed, the array is empty and the loop does not run. This makes methods flexible to handle varying numbers of inputs easily.