Variable declaration and initialization in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of variable initialization with implicit typing

What is the output of this C# code snippet?

C Sharp (C#)

var number = 10;
var text = "Hello";
var result = number + text.Length;
Console.WriteLine(result);

A 15

B Hello10

C 10

D Compilation error

💡 Hint

Remember that var infers the type and text.Length returns an integer.

The variable 'number' is 10, 'text.Length' is 5, so adding them results in 15.

❓ Predict Output

intermediate

Value of uninitialized variable

What happens when you try to use an uninitialized local variable in C#?

C Sharp (C#)

int x;
// Console.WriteLine(x); // Uncommenting this line causes what?

A Compilation error: Use of unassigned local variable 'x'

B Outputs 0

C Outputs garbage value

D Runtime exception

💡 Hint

Local variables must be assigned before use in C#.

Local variables in C# must be initialized before use, otherwise compilation fails.

❓ Predict Output

advanced

Output of variable shadowing in nested scopes

What is the output of this C# code?

C Sharp (C#)

int value = 5;
{
    int value = 10;
    Console.WriteLine(value);
}
Console.WriteLine(value);

A 10\n10

B 5\n10

C 10\n5

D Compilation error due to duplicate variable declaration

💡 Hint

Check if C# allows redeclaring a variable with the same name in an inner block.

C# does not allow redeclaring a variable with the same name in an inner scope if the outer variable is still in scope, so this causes a compilation error.

❓ Predict Output

advanced

Output of nullable variable initialization and usage

What is the output of this C# code?

C Sharp (C#)

int? number = null;
number ??= 100;
Console.WriteLine(number);

A null

B 0

C 100

D Compilation error

💡 Hint

The ??= operator assigns the value only if the variable is null.

Since 'number' is null, the ??= operator assigns 100 to it, so output is 100.

🧠 Conceptual

expert

Behavior of const and readonly variables

Which statement about const and readonly variables in C# is correct?

A const variables can be assigned in constructors; readonly variables cannot.

B const variables can be assigned only at declaration and are compile-time constants; readonly variables can be assigned at declaration or in constructor and are runtime constants.

C Both const and readonly variables can be assigned multiple times during runtime.

D readonly variables can be assigned only at declaration and are compile-time constants; const variables can be assigned anywhere and are runtime constants.

💡 Hint

Think about when the values are fixed and where assignments are allowed.

const variables are fixed at compile time and assigned only once at declaration; readonly variables can be assigned once at declaration or in constructor, allowing runtime initialization.