Array as reference type behavior in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of modifying array through reference

What is the output of the following C# code?

C Sharp (C#)

int[] arr = {1, 2, 3};
int[] refArr = arr;
refArr[0] = 10;
Console.WriteLine(arr[0]);

A 0

B 1

C Compilation error

D 10

💡 Hint

Arrays in C# are reference types, so changes via one reference affect the original array.

Both 'arr' and 'refArr' point to the same array in memory. Changing refArr[0] changes arr[0].

❓ Predict Output

intermediate

Effect of reassigning array reference

What is the output of this C# code snippet?

C Sharp (C#)

int[] original = {5, 6, 7};
int[] copy = original;
copy = new int[] {1, 2, 3};
Console.WriteLine(original[0]);

A 5

B 1

C 0

D Runtime error

💡 Hint

Reassigning 'copy' does not change 'original'.

'copy' initially points to 'original' array, but after reassignment it points to a new array. 'original' remains unchanged.

🔧 Debug

advanced

Why does this array modification not affect original?

Consider this code: int[] a = {1, 2, 3}; ModifyArray(a); Console.WriteLine(a[0]); void ModifyArray(int[] arr) { arr = new int[] {9, 8, 7}; } Why does the output remain 1?

C Sharp (C#)

int[] a = {1, 2, 3};
ModifyArray(a);
Console.WriteLine(a[0]);

void ModifyArray(int[] arr) {
    arr = new int[] {9, 8, 7};
}

A Because arrays are value types and passed by value

B Because the new array is assigned but not returned

C Because the parameter 'arr' is a copy of the reference, reassignment doesn't affect original

D Because the method does not modify any element of the original array

💡 Hint

Think about how references are passed to methods in C#.

The method parameter 'arr' is a copy of the reference. Reassigning it points it to a new array, but does not change the caller's reference.

❓ Predict Output

advanced

Output after modifying array element inside method

What is the output of this C# code?

C Sharp (C#)

int[] nums = {4, 5, 6};
ChangeFirst(nums);
Console.WriteLine(nums[0]);

void ChangeFirst(int[] arr) {
    arr[0] = 100;
}

A 100

B Compilation error

C 0

D 4

💡 Hint

Modifying elements of the array affects the original array.

The method changes the first element of the array that both 'nums' and 'arr' reference.

🧠 Conceptual

expert

Understanding array reference behavior with multiple assignments

Given the code below, what is the final output?

C Sharp (C#)

int[] x = {1, 2};
int[] y = x;
x[0] = 10;
y = new int[] {3, 4};
x[1] = 20;
Console.WriteLine(string.Join(",", y));

A 10,20

B 3,4

C 1,2

D 10,2

💡 Hint

Remember that 'y' is reassigned to a new array after 'x' is modified.

'y' initially points to the same array as 'x'. After reassignment, 'y' points to a new array {3,4}. The Console.WriteLine prints the contents of 'y', which is now {3,4}.