Top-level statements in modern C# - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple top-level statement program

What is the output of this C# program using top-level statements?

C Sharp (C#)

using System;
Console.WriteLine("Hello from top-level statements!");

A No output, program does nothing

B Runtime error: entry point not found

C Hello from top-level statements!

D Compilation error: missing Main method

💡 Hint

Top-level statements allow code directly in the file without a Main method.

In modern C#, top-level statements let you write code directly without defining a Main method explicitly. The program runs and prints the message.

❓ Predict Output

intermediate

Variable scope in top-level statements

What will be the output of this program?

C Sharp (C#)

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

A 10\n5

B 5\n10

C Compilation error: variable 'x' already declared

D 10\n10

💡 Hint

Variables declared inside a block can shadow outer variables.

The inner block declares a new variable x = 10, which shadows the outer x = 5. The first WriteLine prints 10, the second prints 5.

🔧 Debug

advanced

Identify the error in top-level statements with async Main

This program uses top-level statements with async code. What error will it produce?

C Sharp (C#)

using System.Threading.Tasks;

async Task<int> GetNumberAsync() {
    await Task.Delay(100);
    return 42;
}

int result = GetNumberAsync().Result;
Console.WriteLine(result);

A Compilation error: async method not awaited

B Deadlock or runtime hang

C Output: 42

D Runtime exception: NullReferenceException

💡 Hint

Blocking on async code with .Result can cause deadlocks.

Calling .Result on an async method in top-level statements can cause a deadlock because the synchronization context waits for the task to complete while blocking the thread.

❓ Predict Output

advanced

Using namespaces with top-level statements

What is the output of this program?

C Sharp (C#)

namespace MyApp {
    Console.WriteLine("Inside namespace");
}
Console.WriteLine("Outside namespace");

A Compilation error: statements not allowed directly inside namespace

B Inside namespace\nOutside namespace

C Only Outside namespace

D Runtime error: invalid namespace usage

💡 Hint

Top-level statements cannot be placed directly inside a namespace block.

In C#, top-level statements must be at the file root, not inside namespaces. This code causes a compilation error.

🧠 Conceptual

expert

Order of execution in multiple top-level statement files

If a C# project has two files with top-level statements, File1.cs and File2.cs, which statement is true about their execution order?

A Files execute in alphabetical order by filename

B The file listed first in the project file executes first

C The compiler merges all top-level statements into a single Main method in source order

D Execution order is undefined and should not be relied upon

💡 Hint

Top-level statements from multiple files are combined but order is not guaranteed.

The C# compiler merges top-level statements from all files into one Main method, but the order depends on compilation order which is not guaranteed. Relying on execution order across files is unsafe.