Deck 23: Asynchronous Programming With Async and Await

Question 1

________ programming is a technique for writing apps containing tasks that can execute asynchronously,which can improve app performance and GUI responsiveness in apps with long-running or compute-intensive tasks.

A) synchronous
B) object-oriented
C) task-oriented
D) Asynchronous

Answer 1

D
Asynchronous programming

Question 2

Class Task is part ofNET's Task Parallel Library (TPL)for asynchronous programming.Task static method Run receives a ________ as an argument and executes a method in a separate thread.The method returns a Task< TResult > where TResult represents the type of value returned by the method being executed.

A) callback
B) Func< TResult > delegate
C) Task
D) thread

Answer 2

B
Func< TResult > delegate

Question 3

The _________ delegate represents any method that takes no arguments and returns a result.

A) Func< TResult >
B) async
C) task
D) TResult

Answer 3

A
Func< TResult >.

Question 4

When an async method encounters an await expression: If the asynchronous task has already completed,________.

A) the async method simply continues executing
B) the async method splits off another thread
C) the await method is called
D) the async method terminates

Question 5

The async ________ and await _________ greatly simplify asynchronous programming,reduce errors and enable your apps to take advantage of the processing power in today's multicore computers,smartphones and tablets.

A) modifier, operator
B) modifier, modifier
C) operator, operator
D) operator, modifier

Question 6

The async modifier indicates that a method or ________ expression contains at least one await expression.

A) attribute
B) lambda
C) property
D) iterator

Question 7

The async and await mechanism does not create new threads.The method that you call to start an asynchronous task on which you ________ the results is responsible for creating any threads that are used to perform the asynchronous task.

A) await
B) process
C) discard
D) save

Question 8

If a long-running calculation were to be performed synchronously in a GUI app,________.

A) the GUI app would split off the long-running calculation into a separate thread.
B) the GUI would freeze until the calculation completed and the user would not be able to interact with the app
C) the app would terminate
D) the app would deadlock

Question 9

Today's ________ computers,smartphones and tablets enable computers to perform tasks truly concurrently.
a) large memory
b) multiscreen
c) soft keyboard
d) multicore

Question 10

Many classes for web access,file processing,networking,image processing and more contain methods that return ________ objects for use with async and await,so you can take advantage of the asynchronous programming model.

A) threads
B) Task
C) Transient
D) Token

Question 11

A method is declared async to indicate to the compiler that the method will ________.

A) wait for a callback
B) perform a synchronous activity
C) create multiple threads
D) await an asynchronous task

Question 12

When you await a Task,if that Task has already completed,execution simply continues.Otherwise,control returns to ________ until the result of the Task is available.Once the Task completes,the async method continues execution.

A) the async method
B) the await clause
C) the async method's caller
D) the await method's caller

Question 13

Only computers that have ________ can truly execute multiple asynchronous tasks concurrently.

A) a processor
B) multiple processors or cores
C) very large memories
D) two of each type of I/O device

Question 14

Visual C# apps can have multiple threads of execution,where each thread has its own ________ stack,allowing it to execute concurrently with other threads while sharing with them application-wide resources such as memory and processors.This capability is called multithreading.

A) method-call
B) attribute
C) memory
D) application

Question 15

A Task promises to ________.

A) behave itself
B) run to completion
C) create multiple threads
D) return a result at some point in the future

Question 16

An async method executes its body in ________.

A) the calling method
B) the called method
C) the main method
D) the same thread as the calling method

Question 17

The mechanisms for determining whether to return control to the async method's caller or continue executing the async method,and for continuing the async method's execution when the asynchronous task completes are handled by ________.

A) a .NET library routine
B) a user-defined method
C) a custom interface
D) code that's written for you by the compiler

Question 18

Tasks that proceed independently of one another are said to execute ________ and are referred to as ________ tasks.

A) synchronously, synchronous
B) independently, independent
C) asynchronously, asynchronous
D) intensively, intensive

Question 19

Task property ________ returns the value returned by a Task.

A) Result
B) Value
C) TaskReturn
D) TaskValue

Question 20

In effect,an async method allows you to write code that looks like it executes ________,while the compiler deals with the complicated issues of managing asynchronous execution.

A) efficiently
B) outside any method
C) sequentially
D) repeatedly

Question 21

Handling short computations in the GUI thread ________.

A) does not cause the GUI to become unresponsive
B) makes the GUI appear choppy.
C) indefinitely potpnes the GUI.
D) deadlocks the GUI.

Question 22

An async method can perform other statements between those that launch an asynchronous Task and await the Task's results.In such as case,the method continues executing those statements after launching the asynchronous Task until it reaches ________.

A) the await expression
B) the return statement
C) the Task return
D) the async return

Question 23

A ListBox's ________ property indicates which property of each item in the data source should be displayed in the ListBox.

A) ShowProperty
B) SelectProperty
C) DisplaySourceItem
D) DisplayMember

Question 24

A MethodInvoker (namespace System.Windows.Forms)is a ________.

A) a single-argument constructor
B) Delegate that invokes a method with no arguments and a void return type
C) an interface that must be implemented
D) an indirect proxy caller

Question 25

Because ________,asynchronous Tasks are frequently used in GUI apps that invoke web services (or perform network communication in general)to ensure that the apps remain responsive.

A) there can be unpredictably long delays while awaiting a web-service response
B) synchronous tasks don't work well in GUI apps
C) web services are not designed to work with synchronous Tasks
D) memory is limited in GUI-based web services

Question 26

Executing asynchronous methods in separate threads on a dual-core computer typically ________ executing the same tasks sequentially.

A) takes more time than
B) takes about the same amount of time as
C) takes less time than
D) takes an unpredictable amount of time compared to

Question 27

Task static method ________ enables you to wait for any one of several Tasks specified as arguments to complete-the method returns the Task that completes first.

A) FirstToComplete
B) AnyMethod
C) OneOfSeveral
D) WhenAny

Question 28

Which of the following statements is false

A) ProgressBar property Minimum gets or sets a ProgressBar's minimum value.
B) ProgressBar property Maximum gets or sets a ProgressBar's maximum value.
C) ProgressBar property Value gets or sets a ProgressBar's current value. As this number increases, a ProgressBar fills with color.
D) None of the above is false.

Question 29

You can wait for multiple Tasks to complete by awaiting the result of Task static method ________.

A) whenAny
B) WhenAll
C) when
D) whenTask

Question 30

You cannot bind a LINQ query's result directly to a ListBox.You must first ________.

A) bind the result to a ListItem
B) clear the ListBox
C) convert the results to a List with method ToList
D) cast the result to a ListBoxItem

Question 31

A ListBox's ________ property indicates the source of the data that populates the ListBox's Items collection.

A) DataSource
B) DataOrigin
C) DataCreator
D) DataIssuer

Question 32

An app that performs synchronous tasks on a single-core computer often takes longer to execute than on a multi-core computer,because ________.

A) it's too costly to convert them to asynchronous tasks
B) the processor is shared between the app and all the others that happen to be executing on the computer at the same time
C) multi-core computers have no overhead
D) single-core compters generally have slower processors

Question 33

WebClient's ________ method terminates its executing asynchronous task.

A) TerminatePendingRequests
B) CancelPendingRequests
C) DeletePendingRequests
D) RemovePendingRequests

Question 34

Executing calculations in multiple threads on a single-core processor can actually take ________ compared to simply performing them synchronously,due to the overhead of sharing one processor among the app's threads,all the other apps executing on the computer at the same time and the chores the operating system was performing.

A) less time
B) more time
C) about the same amount of time
D) much less time

Question 35

Class HttpClient's ________ method starts a new Task< string > in a separate thread and uses the URL specified as the method's string argument to request information from a web server.

A) RequestWebStringAsync
B) QueryWebStringAsync
C) StartTaskStringAsync
D) GetStringAsync

Question 36

Enumerable static method ________ creates a list of elements containing the first argument's value.The length of the list is specified by the second argument.

A) Enumerate
B) Repeat
C) Generate
D) None of the above.

Question 37

When updating a control from a non-GUI thread,you must ________.

A) launch a separate thread to perform the update
B) notify the GUI thread that you'll be updating it in another thread
C) ensure that the update doesn't corrupt the GUI thread's activities.
D) schedule that update to be performed by the GUI thread