Array indexing and access in C Sharp (C#) - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the starting index of arrays in C#?

Arrays in C# start indexing at 0. This means the first element is at index 0, the second at index 1, and so on.

beginner

How do you access the third element of an array named numbers?

You access it using numbers[2] because indexing starts at 0.

intermediate

What happens if you try to access an index outside the array bounds in C#?

You get a System.IndexOutOfRangeException error because the index is invalid.

beginner

How can you find the length of an array named items?

Use items.Length to get the number of elements in the array.

beginner

Explain how to change the value of the first element in an array colors to "red".

Assign the new value using colors[0] = "red"; to update the first element.

What is the index of the last element in an array with 10 elements?

A 9

B 10

C 0

D 11

Since indexing starts at 0, the last element is at index 9 (10 - 1).

Which of the following accesses the second element of an array named arr?

A arr[2]

B arr[1]

C arr[0]

D arr[3]

The second element is at index 1 because indexing starts at 0.

What property gives the number of elements in a C# array?

A Length

B Count

C Size

D Capacity

The Length property returns the number of elements in the array.

What error occurs if you try to access array[10] when the array has 10 elements?

A NullReferenceException

B InvalidOperationException

C ArgumentException

D IndexOutOfRangeException

Accessing index 10 is out of bounds since valid indices are 0 to 9, causing an IndexOutOfRangeException.

How do you change the value of the first element in an array named data?

A data.change(0, newValue);

B data[1] = newValue;

C data[0] = newValue;

D data.set(0, newValue);

You assign the new value directly using the index: data[0] = newValue;.

Describe how array indexing works in C# and how to access elements safely.

Think about how you count positions starting from zero.

Explain how to update an element in a C# array and what happens if you try to access an invalid index.

Consider what happens if you try to open a door that doesn't exist.