Difference between Constant and Readonly

Constant : The constants are the one whose value remain same at all the time.
it will be used if u want to define something at compile time.

Read only:

if you don't know value at compile time but u can find that at runtime that time u can use readonly ..

Read only are the things which are not to allowed to alter by the user but it can be altered by itself. Readonly is generally use in Constructor of the classes.

Like the path of the application exe is read only. If you copy exe to some other directory the path will change. But still it is read only

Interface Vs Delegate

Interfaces allow us to extend some object's functionality, it's a contract
between the interface and the object that implements it. It is used to
simulate multiple inheritance in C#. In the other hand, we have delegates...
They're just safe callbacks or function pointers. They allow us to notify
that something has happened (Events). As you can see they're different as
well as their use.

Interview Questions on UML

What is UML?

UML is Unified Modeling Language. It is a graphical language for visualizing specifying constructing and documenting the artifacts of the system. It allows you to create a blue print of all the aspects of the system, before actually physically implementing the system.

What is modeling? What are the advantages of creating a model?

Modeling is a proven and well-accepted engineering technique which helps build a model. Model is a simplification of reality; it is a blueprint of the actual system that needs to be built. Model helps to visualize the system. Model helps to specify the structural and behavior of the system. Model helps make templates for constructing the system. Model helps document the system.

What are the different views that are considered when building an object-oriented software system?

Normally there are 5 views. Use Case view - This view exposes the requirements of a system. Design View - Capturing the vocabulary. Process View - modeling the distribution of the systems processes and threads. Implementation view - addressing the physical implementation of the system. Deployment view - focus on the modeling the components required for deploying the system.
What are diagrams? Diagrams are graphical representation of a set of elements most often shown made of things and associations.

What are the major three types of modeling used?
Major three types of modeling are structural, behavioral, and architectural.

Mention the different kinds of modeling diagrams used?
Modeling diagrams that are commonly used are, there are 9 of them. Use case diagram, Class Diagram, Object Diagram, Sequence Diagram, statechart Diagram, Collaboration Diagram, Activity Diagram, Component diagram, Deployment Diagram.

What is Architecture?
Architecture is not only taking care of the structural and behavioral aspect of a software system but also taking into account the software usage, functionality, performance, reuse, economic and technology constraints.

What is SDLC?
SDLC is Software Development Life Cycle. SDLC of a system included processes that are Use case driven, Architecture centric and Iterative and Incremental. This Life cycle is divided into phases. Phase is a time span between two milestones. The milestones are Inception, Elaboration, Construction, and Transition. Process Workflows that evolve through these phase are Business Modeling, Requirement gathering, Analysis and Design, Implementation, Testing, Deployment. Supporting Workflows are Configuration and change management, Project management.

What are Relationships?
There are different kinds of relationships: Dependencies, Generalization, and Association. Dependencies are relations ships between two entities that that a change in specification of one thing may affect another thing. Most commonly it is used to show that one class uses another class as an argument in the signature of the operation. Generalization is relationships specified in the class subclass scenario, it is shown when one entity inherits from other. Associations are structural relationships that are: a room has walls, Person works for a company. Aggregation is a type of association where there is a has a relation ship, That is a room has walls, ño if there are two classes room and walls then the relation ship is called a association and further defined as an aggregation.

How are the diagrams divided?
The nine diagrams are divided into static diagrams and dynamic diagrams.
Static Diagrams (Also called Structural Diagram): Class diagram, Object diagram, Component Diagram, Deployment diagram.
Dynamic Diagrams (Also called Behavioral Diagrams): Use Case Diagram, Sequence Diagram, Collaboration Diagram, Activity diagram, Statechart diagram.

What are Messages? A message is the specification of a communication, when a message is passed that results in action that is in turn an executable statement.

What is an Use Case?
A use case specifies the behavior of a system or a part of a system, óse cases are used to capture the behavior that need to be developed. It involves the interaction of actors and the system.

What is observableCollection in WPF

In many cases the data that you work with is a collection of objects. For example, a common scenario in data binding is to use anItemsControl such as a ListBox, ListView, or TreeView to display a collection of records.
You can enumerate over any collection that implements the IEnumerable interface. However, to set up dynamic bindings so that insertions or deletions in the collection update the UI automatically, the collection must implement the INotifyCollectionChanged interface. This interface exposes the CollectionChanged event, an event that should be raised whenever the underlying collection changes.
WPF provides the ObservableCollection(T) class, which is a built-in implementation of a data collection that implements theINotifyCollectionChanged interface.
Before implementing your own collection, consider using ObservableCollection(T) or one of the existing collection classes, such as List(T),Collection(T), and BindingList(T), among many others. If you have an advanced scenario and want to implement your own collection, consider using IList, which provides a non-generic collection of objects that can be individually accessed by index. Implementing IList provides the best performance with the data binding engine.

What is SaaS

Software as a service (or SaaS) is a way of delivering applications over the Internet—as a service. Instead of installing and maintaining software, you simply access it via the Internet, freeing yourself from complex software and hardware management.

SaaS applications are sometimes called Web-based software, on-demand software, or hosted software. Whatever the name, SaaS applications run on a SaaS provider’s servers. The provider manages access to the application, including security, availability, and performance.

What are the three kinds of routed events in WPF and how do they differ?

Routed events in WPF are direct, tunneling a bubbling. A direct event can be raised only by the element in which it originated. A bubbling event is raised first by the element in which it originates and then is raised by each successive container in the visual tree. A tunneling event is raised first by the topmost container in the visual tree and then down through each successive container until it is finally raised by the element in which it originated. Tunneling and bubbling events allow elements of the user interface to respond to events raised by their contained elements.

What is the difference between Navigation applicaton and XBAPs in WPF?

While both are page-based applications. Navigation Page application are used for navigation applicated hosted with full trust policy that makes them ideal for deployment in secure environment. XBAPs are generally design for Window Explorer and are not locally installed. They are partial trust application restricted to use local file system, Database, registries and other sensitive resources and this makes them ideal for wide distribution