Telephone Interview – Cheat Sheet

WCF

  • Support for strongly and loosely typed messages
  • Support for bindings
  • Support for the latest web services
  • Integrated security model
  • Stateful/stateless
  • Boundaries are explicit
  • Services are autonomous
  • Communication via contract
  • ABC

[ServiceContract] – service interface, name, namespace, protectionlevel, CallbackContract,

Session – Required, Allowed, NotAllowed

ProtectionLevel – encryption, digital signatures

[OperationContract] – method, IsOneWay, AsyncPattern, IsInitiating, IsOneWay, IsTerminating

[ServiceBehaviour] – PerCall, PerSession, Single

ConcurrencyMode –  Single, Multple, Reentrant

[DataContract]

[DataMember]

[FaultContract(typeof(DataContract)]

 

Bindings

BasicHttpBinding – default, one direction

WSHttpBinding – More webservice features – transactions

WSDualHttpBinding – Duplex communication

NetNamedPipeBinding – Same machine

NetPeerTcpBinding – P2P network

NetTcpBinding – Duplex TCP binding

MsmqIntegrationBinding – to existing application using Msmq

NetMsmqBinding – Between .Net applications

 

Hosting

System.ServiceModel.dll

<services>

<service name = “Name”>

<endpoint address = http://localhost:8080/ServiceName

binding = “basicHttpBinding”

contract = “IServiceContract” />

</services>

 

ServiceHost host = new ServiceHost(typeof(MyService), “Uri”)

host.Open()

 

MEX

Meta data about service

Allows to create proxies

svcutil

 

Configuration

OpenTimeout

CloseTimeout

SvcConfigEditor

 

IsInitiating – create instance

IsTerminating – close instance

PerSession – default is 10 mins, inactivityTimeout, AutomaticSessionShutdown = false – explicit call to close the session

 

 

WPF

PresentationCore.dll, PresentationFramework.dll, System.Xaml.dll, WindowsBase.dll

DispatcherObject – Dispatcher

DependencyObject – dependency properties

UIElement – events, Focusable, IsEnabled, IsMouse….Over, Visibility, RenderTransform

FrameworkElement – storyboarding, databinding, Name property

DependencyProperty – animation, binding, DependencyPropery.Register(), inheritance, triggers, Callbacks, Coercetion

AttachedProperty – DependencyProperty.RegisterAttached

Markup Extensions – {}, extend grammar of XAML

 

Panel Controls

Canvas, DockPanel, Grid, StackPanel, WrapPanel, UniformGrid

 

Triggers

Trigger – dependency property

MultiTrigger – same as Trigger but with multiple conditions

EventTrigger – particular event has occurred, applies animation

DataTrigger – a property in datacontext has reached some value

DataTemplates – associating data context with a view

ControlTemplates – Override the whole visual representation of the control

TemplateBinding – RelativeSource{RelativeSource=TemplatedParent} or {TemplatedBinding Padding} (won’t work if you need two way}

 

Routed Events

Buble Events –

Tunnel Events – Preview….

Direct Events

EventManager.RegisterRoutedEvent(“Click”, RoutingEventStrategy.Bubble, typeof(RoutedEventHandler), typeof(ButtonBase));

Freezable – makes the object immutable

WPF Performance Tuning

Dispatcher.BeginInvoke / BackgroundWorker

Fix Binding Errors

Prevent Software Rendering – BitMapEffects

Virtualise Lists

Freeze Freezables

Disable Assembly Localisation

Lower Framerate of animations

 

Troubleshooting

Scrollbar is not visible – ??

Databinding –

 

Bindings

Static – compile time

Dynamic – runtime

ElementName, Path

Relative Source – Self, FindAncestor, PreviousItem,

 

Styles

Styles – <Style x:Key=”Name”>

<Setter Property = “Name” Value=”14”/>

</Style>

Animations

BooleanAnimationUsingKeyFrames, ColorAnimation, DecimalAnimation, Int32AnimationUsingKeyFrames

IDataError

ErrorTemplate

Data Views

ListCollectionView view = CollectionViewSource.GetDefaultView(source) as ListCollectionView;

PropertyGroupDescription

Dispatcher

Own the application thread and manages the queue of work items.

Dispatcher.CurrentDispatcher

 SQL

 1NF: Eliminate Repeating Groups

Make a separate table for each set of related attributes, and give each table a primary key. Each field contains at most one value from its attribute domain.

2NF: Eliminate Redundant Data

If an attribute depends on only part of a multi-valued key, remove it to a separate table.

3NF: Eliminate Columns Not Dependent On Key

If attributes do not contribute to a description of the key, remove them to a separate table. All attributes must be directly dependent on the primary key

 Index

An index is a physical structure containing pointers to the data. Indices are created in an existing table to locate rows more quickly and efficiently

Clustered indexes define the physical sorting of a database table’s rows in the storage media. For this reason, each database table may have only one clustered index.

Non-clustered indexes are created outside of the database table and contain a sorted list of references to the table itself.

Primary Key – creates a clustered index, cannot be null

Unique Key – non-nonclustered index by default, can be null

Delete – can have where clause, foreign keys are checked, activates triggers

Truncate – will remove data and reset auto increment. Truncate is not logger, cannot be rolled back

Function – can be used in WHERE/HAVING/SELECT

UPDATE_STATISTICS – after large dataset has been processed

Joins – INNER JOIN, OUTER JOIN, CROSS JOIN, LEFT JOIN, RIGHT JOIN

Log Shipping – the process of automating back up of database and transaction log files

Replication – Snapshot, Transaction – updates, Merge – updates when connected

Permissions

GRANT/DENY/REVOKE

Execution Plan

An execution plan is basically a road map that graphically or textually shows the data retrieval methods chosen by the SQL Server query optimizer for a stored procedure or ad-hoc query

Wildcats – % any group of characters, _ – single character, [ab] – a or b

Locks – Shared locks – SELECT, Update locks – to update a page, Exclusive Locks – UPDATE/DELETE/INSERT

Triggers – UPDATE/INSERT/DELETE

Instead of Triggers – ignored instead the code is fired

Transaction Isolation Levels

READ UNCOMMITED – can read data that has been modified but not yet committed. Dirty reads. Phantom reads

READ COMMITED – cannot read that has been modified but not yet committed. No dirty read. Default. Phantom reads

REPEATABLE READS – no other transaction can read data that has been modified by the current transaction until it’s committed. Phantom reads

SNAPSHOT – does not require read locks. Takes snapshot. Data modifications made by other transactions are not visible by this transaction

SERIALIZABLE – cannot read until committed, no other transaction can modify data

.NET Performance

Reference Type Internals – Object Header Word (-4), Method Table Pointer (+0), Storage for_id (+4), Storage for_name (+8)

  • Object Header Word – Sync Block Index, HashCode storage,
  • Aligned to 4 or 8 bytes

Value Types – compact, implement IEquitable<T>

LOH – 85KB, not compacted

Finalisation – added to finalization queue, removes the reference to that object, moves to f-reachable queue. Finalizer is run on finalization thread

GC Process

Mark Phase – find a list of all live objects

Relocating – changes references to the objects that will be compated

Compation – Moved objects towards the older end of the segment

Workstation GC is only used on single CPU pcs

Concurrent GC – can allocate on Gen0 and Gen1 if have free space, otherwise have to wait for collection.

Background GC – objects in Gen0 and Gen1 are collected as normal even though the collection in Gen2 is taking place.

System.Runtime.GCSettings

  • Batch – for applications that have no UI or server side applications
  • Interactive – for UI applications
  • LowLatency – minimizes latency short term
  • SustainedLowLatency

 

Design

Creational

Abstract Factory groups object factories that have a common theme.

Builder constructs complex objects by separating construction and representation.

Factory Method creates objects without specifying the exact class to create.

Prototype creates objects by cloning an existing object.

Singleton restricts object creation for a class to only one instance.

 

Structural

Adapter allows classes with incompatible interfaces to work together by wrapping its own interface around that of an already existing class.

Bridge decouples an abstraction from its implementation so that the two can vary independently.

Composite composes zero-or-more similar objects so that they can be manipulated as one object.

Decorator dynamically adds/overrides behaviour in an existing method of an object.

Facade provides a simplified interface to a large body of code.

Flyweight reduces the cost of creating and manipulating a large number of similar objects.

Proxy provides a placeholder for another object to control access, reduce cost, and reduce complexity.

 

Behavioral

Chain of responsibility delegates commands to a chain of processing objects.

Command creates objects which encapsulate actions and parameters.

Interpreter implements a specialized language.

Iterator accesses the elements of an object sequentially without exposing its underlying representation.

Mediator allows loose coupling between classes by being the only class that has detailed knowledge of their methods.

Memento provides the ability to restore an object to its previous state (undo).

Observer is a publish/subscribe pattern which allows a number of observer objects to see an event.

State allows an object to alter its behavior when its internal state changes.

Strategy allows one of a family of algorithms to be selected on-the-fly at runtime.

Template method defines the skeleton of an algorithm as an abstract class, allowing its subclasses to provide concrete behavior.

Visitor separates an algorithm from an object structure by moving the hierarchy of methods into one object.

 

SOLID Principles

Single Responsibility

Open Closed principle

Liskov substitution principle

Interface segregation principle

Dependency Inversion Principle

 

FIX Protocol

1 – Account Id

8 – BeginString

9 – BodyLength

35 – MessageType

34 – MsgSeqNo

49 – SenderCompId

56 – TargetCompId

One Comment on “Telephone Interview – Cheat Sheet

  1. Pingback: Telephone Interview – Cheat Sheet | IReadable

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