Asp.net and C# Interview Qustions

ASP.NET

1. Where machine.config resides?

32-bit

%windir%\Microsoft.NET\Framework\[version]\config\machine.config

64-bit

%windir%\Microsoft.NET\Framework64\[version]\config\machine.config 

[version] should be equal to v1.0.3705, v1.1.4322, v2.0.50727 or v4.0.30319.

2. How can we prevent browser from caching an ASPX page?

We can SetNoStore on HttpCachePolicy object exposed by the Response object’s Cache property:

1 2	Response.Cache.SetNoStore (); Response.Write (DateTime.Now.ToLongTimeString ());

3. Page Life cycle stages?

Stage	Description
Page request	The page request occurs before the page life cycle begins. When the page is requested by a user, ASP.NET determines whether the page needs to be parsed and compiled (therefore beginning the life of a page), or whether a cached version of the page can be sent in response without running the page.
Start	In the start stage, page properties such as Request and Response are set. At this stage, the page also determines whether the request is a postback or a new request and sets the IsPostBack property. The page also sets the UICulture property.
Initialization	During page initialization, controls on the page are available and each control's UniqueID property is set. A master page and themes are also applied to the page if applicable. If the current request is a postback, the postback data has not yet been loaded and control property values have not been restored to the values from view state.
Load	During load, if the current request is a postback, control properties are loaded with information recovered from view state and control state.
Postback event handling	If the request is a postback, control event handlers are called. After that, the Validate method of all validator controls is called, which sets the IsValid property of individual validator controls and of the page. (There is an exception to this sequence: the handler for the event that caused validation is called after validation.)
Rendering	Before rendering, view state is saved for the page and all controls. During the rendering stage, the page calls the Render method for each control, providing a text writer that writes its output to the OutputStream object of the page's Response property.
Unload	The Unload event is raised after the page has been fully rendered, sent to the client, and is ready to be discarded. At this point, page properties such as Response and Request are unloaded and cleanup is performed.

4. Asp.Net validation control?

1. RequiredFieldValidator.
2. RangeValidator.
3. CompareValidator.
4. RegularExpressionValidator.
5. CustomValidator.
6. ValidationSummary.

C#

1. What is Reflection?

Reflection objects are used for obtaining type information at runtime. The classes that give access to the metadata of a running program are in the System.Reflection namespace.

The System.Reflection namespace contains classes that allow you to obtain information about the application and to dynamically add types, values, and objects to the application.

Reflection has the following applications:

1. It allows view attribute information at runtime.
2. It allows examining various types in an assembly and instantiate these types.
3. It allows late binding to methods and properties
4. It allows creating new types at runtime and then performs some tasks using those types.

2. Difference between Assembly and Namespace?

Assembly will contain Namespaces, Classes, Data types it's a small unit of code for deployment. Assembly defines the name of the .dll file.It also avoids dll hell problem.

Namespace is used in order to avoid conflict of user defined classes.

Namespace:
1) it is a Collection of names wherein each name is Unique.
2) They form the logical boundary for a Group of classes.
3) Namespace must be specified in Project-Properties.

Assembly:
1) It is an Output Unit.
2) It is a unit of Deployment & a unit of versioning.
3) Assemblies contain MSIL code.
4) Assemblies are Self-Describing. [e.g. metadata,manifest]
5)An assembly is the primary building block of a .NET Framework application.
6) It is a collection of functionality that is built, versioned, and deployed as a single implementation unit (as one or more files).
7) All managed types and resources are marked either as accessible only within their implementation unit, or by code outside that unit.

3. What is Metadata?

Metadata in .Net is binary information which describes the characteristics of a resource . This information include Description of the Assembly , Data Types and members with their declarations and implementations, references to other types and members , Security permissions etc. A module's metadata contains everything that needed to interact with another module.

During the compile time Metadata created with Microsoft Intermediate Language (MSIL) and stored in a file called a Manifest . Both Metadata and Microsoft Intermediate Language (MSIL) together wrapped in a Portable Executable (PE) file. During the runtime of a program Just In Time (JIT) compiler of the Common Language Runtime (CLR) uses the Metadata and converts Microsoft Intermediate Language (MSIL) into native code. When code is executed, the runtime loads metadata into memory and references it to discover information about your code's classes, members, inheritance, and so on.

4. What is SOLID principles?

SOLID is basically 5 principles, which will help to create a good software architecture. You can see that all design patterns are based on these principles. SOLID is basically an acronym of the following:

• S is single responsibility principle (SRP)
• O stands for open closed principle (OCP)
• L Liskov substitution principle (LSP)
• I interface segregation principle (ISP)
• D Dependency injection principle (DIP)

5. Difference between IEumerable, ICollection, IList, List?

• IEnumerable<T> is the base interface that the following extend or implement. It doesn't allow for direct access and is readonly. So use this only if you intend to iterate over the collection.
• ICollection<T> extendsIEnumerable<T> but in addition allows for adding, removing, testing whether an element is present in the collection and getting the total number of elements. It doesn't allow for directly accessing an element by index. That would be an O(n) operation as you need to start iterating over it until you find the corresponding element.
• IList<T> extends ICollection<T> (and thus it inherits all its properties) but in addition allows for directly accessing elements by index. It's an O(1) operation.
• List<T> is just a concrete implementation of the IList<T> interface.

6. What Yield Keyword do?

Yield allows each iteration in foreach loop to be generated when required. In this way it improves performance.

7. What is Dependency Injection? In How many ways you can implement dependency injection?

Dependency Injection (DI) is a software design pattern that allow us to develop loosely coupled code. DI is a great way to reduce tight coupling between software components. DI also enables us to better manage future changes and other complexity in our software. The purpose of DI is to make code maintainable.

Three ways you can implement DI

1. Constructor Injection
2. Properties Injection
3. Method Injection