Null-coalescing operator in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of null-coalescing with nullable int

What is the output of this C# code snippet?

C Sharp (C#)

int? a = null;
int b = 5;
int result = a ?? b;
Console.WriteLine(result);

A null

B 0

C Compilation error

D 5

💡 Hint

The null-coalescing operator returns the left value if it is not null; otherwise, it returns the right value.

Since 'a' is null, the operator returns 'b', which is 5.

❓ Predict Output

intermediate

Null-coalescing with strings

What will this program print?

C Sharp (C#)

string s = null;
string result = s ?? "default";
Console.WriteLine(result);

A default

B null

C Compilation error

D Empty string

💡 Hint

If the left side is null, the operator returns the right side.

Since 's' is null, the expression returns "default".

❓ Predict Output

advanced

Chained null-coalescing operators

What is the output of this code?

C Sharp (C#)

string? a = null;
string? b = null;
string c = "hello";
string result = a ?? b ?? c;
Console.WriteLine(result);

A hello

B null

C Compilation error

D Empty string

💡 Hint

The operator evaluates left to right and returns the first non-null value.

Both 'a' and 'b' are null, so the operator returns 'c', which is "hello".

❓ Predict Output

advanced

Null-coalescing with method call

What will this code print?

C Sharp (C#)

string? GetName() => null;

string name = GetName() ?? "Unknown";
Console.WriteLine(name);

A null

B Unknown

C Compilation error

D Empty string

💡 Hint

The method returns null, so the operator returns the fallback string.

GetName() returns null, so the null-coalescing operator returns "Unknown".

❓ Predict Output

expert

Null-coalescing with nullable struct and property

What is the output of this program?

C Sharp (C#)

struct Point { public int X; public int Y; }

Point? p = null;
int x = p?.X ?? -1;
Console.WriteLine(x);

A Compilation error

B 0

C -1

D NullReferenceException

💡 Hint

The null-conditional operator returns null if 'p' is null, so the null-coalescing operator uses -1.

Since 'p' is null, 'p?.X' is null, so the expression evaluates to -1.