C# Interview Question

Question

1.When should you use Abstract class over interface and interface over abstract class? 2.What is different between ArrayList and List? 3.What is reflection in c#? 4.What is different between Debug and Release mode in Visual studio? 5. What would be output? Is this program run or generate compile time error?If run then why? if nor then why? Note : Here i am using private access modifier with main() function. private static void Main() { Console.WriteLine(Hello C#!!); }

Francis · Answer

1.When should you use Abstract class over interface and interface over abstract class? If you want to decide a class to be a Parent at that time you go with Abstract classes. This is the most common scenario. Because Abstract classes can be think of mix of Concrete as well as Contract. But interfaces will contain only Contract. 2.What is different between ArrayList and List? Array list is a non-generic collection. But List (hope you meant List ) comes under generic collection. For more info the below url is helpful to you: http://www.codeproject.com/Tips/855546/What-is-the-Difference-between-ArrayList-and-List 3.What is reflection in c#? Reflection is a class in .Net that is useful in the below scenarios: When you have to access attributes in your program's metadata. For examining and instantiating types in an assembly. For building new types at runtime. For performing late binding accessing methods on types created at run time. Reference: https://msdn.microsoft.com/en-us/library/ms173183.aspx 4.What is different between Debug and Release mode in Visual studio? When you develop an application at that time you will use Debug mode when you decide to take a build (decide to release) at that time you will go with Release mode. 5. Program works fine even you are using private. Hope this helps!

Rajeesh Menoth · Answer

Hi 1.When should you use Abstract class over interface and interface over abstract class? Check this reference : http://codeofdoom.com/wordpress/2009/02/12/learn-this-when-to-use-an-abstract-class-and-an-interface/ http://programmers.stackexchange.com/questions/41740/when-to-use-abstract-classes-instead-of-interfaces-with-extension-methods-in-c 2.What is different between ArrayList and List? http://www.codeproject.com/Tips/855546/What-is-the-Difference-between-ArrayList-and-List 3.What is reflection in c#? Reflection is used to dynamically create an instance of a type bind the type to an existing object or get the type from an existing object and invoke its methods or access its fields and properties. If you are using attributes in your code reflection enables you to access them. Reference : http://www.c-sharpcorner.com/UploadFile/07c1e7/what-is-reflection-in-C-Sharp/ 4.What is different between Debug and Release mode in Visual studio? In Debug Mode your .exe has debug information inside of it (source code variable names and other similar stuff like that). In Release Mode your .exe lack of debug information makes it smaller and probably performs better due to its smaller footprint. 5.What would be output? Is this program run or generate compile time error?If run then why? if nor then why? Working good..!!