Default values for types in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of default values for int and bool?

Consider the following C# code snippet. What will be printed when it runs?

C Sharp (C#)

int defaultInt = default;
bool defaultBool = default;
Console.WriteLine($"{defaultInt}, {defaultBool}");

A null, False

B 0, true

C 0, False

D null, true

💡 Hint

Default value of int is zero and default value of bool is false.

In C#, default for int is 0 and for bool is false. So the output is 0, False.

❓ Predict Output

intermediate

What is the default value of a reference type?

What will this C# code print?

C Sharp (C#)

string defaultString = default;
Console.WriteLine(defaultString == null ? "null" : defaultString);

A empty string

B null

C 0

D throws NullReferenceException

💡 Hint

Default value of reference types is null.

Reference types like string have null as their default value in C#.

❓ Predict Output

advanced

Default value of a struct with fields

Given this struct and code, what is the output?

C Sharp (C#)

struct Point { public int X; public int Y; }
Point p = default;
Console.WriteLine($"X={p.X}, Y={p.Y}");

A X=0, Y=0

B X=null, Y=null

C X=, Y=

D Compilation error

💡 Hint

Struct fields get default values too.

Struct fields are value types and get default values. So both X and Y are 0.

❓ Predict Output

advanced

Default value of nullable types

What will this code print?

C Sharp (C#)

int? nullableInt = default;
Console.WriteLine(nullableInt.HasValue);

A False

B True

C null

D Compilation error

💡 Hint

Nullable types default to null, so HasValue is false.

Nullable types default to null, so HasValue is false.

🧠 Conceptual

expert

Why does default(T) behave differently for value and reference types?

Which statement best explains the behavior of default(T) in C#?

A It returns zero for all types because zero is the universal default.

B It returns null for all types because all types are reference types.

C It throws an exception if T is a reference type.

D It returns the zero-equivalent for value types and null for reference types because of how memory is allocated.

💡 Hint

Think about how value and reference types store data differently.

Value types have a zero-equivalent default (like 0 for int), while reference types default to null because they store references to objects.