C# Dot Net Interview Preparation Part 7 | Top 6 Frequently Asked Interview Questions and Answers

Question 37: What is the difference between a struct and a class in C#?

Answer:

• Struct: A value type stored on the stack.
• Class: A reference type stored on the heap.

Code Example:

struct MyStruct
{
    public int Value;
}

class MyClass
{
    public int Value;
}

var struct1 = new MyStruct { Value = 10 };
var class1 = new MyClass { Value = 10 };

// Modifying struct1 won't affect copies.
        

Question 38: What is a static class in C#?

Answer: "A static class cannot be instantiated and can only contain static members (fields, methods, properties)."

Code Example:

public static class MathHelper
{
    public static int Add(int a, int b) => a + b;
}

int result = MathHelper.Add(5, 3); // Output: 8
        

Question 39: What is the purpose of GC.Collect() in .NET?

Answer: "GC.Collect() forces garbage collection, clearing unused objects from memory. However, it's better to rely on automatic garbage collection for efficiency."

Code Example:

class Program
{
    static void Main()
    {
        // Allocate memory
        var largeArray = new int[10000];
        GC.Collect(); // Explicitly invoke garbage collection
    }
}
        

Question 40: What is the difference between Array and ArrayList in C#?

Answer:

• Array: Fixed size, stores elements of the same type.
• ArrayList: Dynamically resizable, stores elements of any type (not type-safe).

Code Example:

int[] numbers = new int[3] { 1, 2, 3 }; // Array
ArrayList list = new ArrayList();
list.Add(1);
list.Add("String"); // ArrayList (mixed types)
        

Question 41: What is a thread in .NET, and how do you create one?

Answer: "A thread is the smallest unit of execution in .NET. Multiple threads can run simultaneously for better performance."

Code Example:

using System.Threading;

Thread thread = new Thread(() => Console.WriteLine("Thread started!"));
thread.Start();
        

Question 42: What is the difference between public, private, protected, and internal access modifiers?

Answer:

Access Modifier Description Public Accessible everywhere. Private Accessible only within the containing class. Protected Accessible within the containing class and derived classes. Internal Accessible within the same assembly.

Code Example:

class MyClass
{
    public string PublicProperty { get; set; }
    private int PrivateProperty { get; set; }
    protected double ProtectedProperty { get; set; }
    internal string InternalProperty { get; set; }
}
        

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