Ace Your Sharp Electronics Interview: Insider Tips and Sample Questions

Toptal sourced essential questions that the best C# developers and engineers can answer. Driven from our community, we encourage experts to submit questions and offer feedback.

What is the output of the short program below? Explain your answer.

The output will be:

Although both variables are uninitialized, String is a reference type and DateTime is a value type. The value type of a unitialized DateTime variable is set to midnight on January 1, 2011 (yes, that’s the year 1.01). D. ), not null. 2 .

Given an array of ints, write a C# method to total all the values that are even numbers.

There are of course many ways to do this, but two of the most straightforward would be either:

or:

Here are the key things to look for in the answer:

• Does the candidate take advantage of the C# language constructs which make a one-liner solution possible (i. e. , instead of using a longer solution with a loop, a conditional statement, and an accumulator)?
• Does the candidate consider the possibility of overflow. For example, an implementation such as return intArray. Where(i => i % 2 == 0). Sum(), no matter what kind of return type the function has, might be an “obvious” one-line answer, but there is a high chance that it will overflow. Converting to long in the answers above doesn’t completely rule out the chance of an overflow exception happening, but it makes it very unlikely. Keep in mind that if the candidate asks about the expected size of the array and the size of its elements, it’s clear that they are thinking about this overflow problem, which is part of what we want to find out.

3 .

Should the following if statement compare time and null or not? If not, explain why it shouldn’t work.

Since a DateTime variable is always set to January 1, 0001, you might think that the compiler would complain when a DateTime variable is compared to null. But because of type coercion, the compiler does let it happen, which could cause headfakes and bugs that make you want to pull out your hair.

In more detail, the == operator will change the types of its operands to different ones so that both sides have the same type, which it can then compare. That’s why this will give you the result you want (rather than failing or acting in a way you didn’t expect because the operands are different types):

This can sometimes lead to strange behavior, though. For example, when you compare a DateTime variable to null, In such a case, both the DateTime variable and the null literal can be cast to Nullable. Therefore it is legal to compare the two values, even though the result will always be false.

Apply to Join Toptals Development Network

and enjoy reliable, steady, remote Freelance C# Developer Jobs

Given an instance circle of the following class:

write code to calculate the circumference of the circle, without modifying the Circle class itself.

The preferred answer would be of the form:

We tell the object to figure out the circumference by passing it the calculation function inline since we can’t get to its private radius field in this case.

A lot of C# programmers shy away from (or don’t understand) function-valued parameters. Even though this example is a bit made up, the point is to see if the applicant knows how to write a call to Calculate that matches the method’s definition.

On the other hand, you could get the object’s radius value and use that to do the calculation, which would be valid but less elegant:

Either way works. What we’re mostly interested in is whether or not the candidate knows about and can use the Calculate method. 5 .

What is the output of the program below? Explain your answer.

Also, would the answer change if we were to replace await Task.Delay(5); with Thread.Sleep(5)? Why or why not?

The answer to the first part of the question (i. e. , the version of the code with await Task. Delay(5);) is that the program will just output a blank line (not “Hello world!”). This is because result will still be uninitialized when Console. WriteLine is called.

Most procedural and object-oriented programmers expect a function to run all the way through to a return statement or the end before going back to the function that called it. This is not the case with C# async functions. They only execute up until the first await statement, then return to the caller. The function called by await (in this case Task. Delay) is executed asynchronously, and the line after the await statement isn’t signaled to execute until Task. Delay completes (in 5 milliseconds). However, within that time, control has already returned to the caller, which executes the Console. WriteLine statement on a string that hasn’t yet been initialized.

Calling await Task. Delay(5) lets the current thread keep doing what it’s doing and returns it to the thread pool if it’s done (as long as there are no awaits). This is the primary benefit of the async/await mechanism. It allows the CLR to service more requests with less threads in the thread pool.

With the rise of devices that can make service or database requests over the network for many tasks, asynchronous programming has become a lot more common. C# has some excellent programming constructs which greatly ease the task of programming asynchronous methods, and a programmer who is aware of them will produce better programs.

With regard to the second part of the question, if await Task. Delay(5); was replaced with Thread. Sleep(5), the program would output Hello world!. If an async method doesn’t have at least one await statement, it works the same way as a synchronous method, which means it will run from start to finish or until it hits a return statement. Calling Thread. Sleep() simply blocks the currently running thread, so the Thread. Sleep(5) call just adds 5 milliseconds to the execution time of the SaySomething() method. 6 .

What is the output of the program below? Explain your answer.

This program will output the number 10 ten times.

This is because the delegate is added in the for loop, and a “reference” (or maybe “pointer” would be a better word) to i is stored instead of the value itself. So, when we get out of the loop, the variable i is set to 10, and when each delegate is called, they are all given the value 10. 7 .

It is possible to store mixed datatypes such as int, string, float, char all in one array?

Yes, you can do that because the array can be of type object, which can hold any type of data as well as the class object shown below:

Compare structs and classes in C#. What do they have in common? How do they differ?

Classes and Structs in C# do have a few things in common, namely:

• Are compound data types
• Can contain methods and events
• Can support interfaces

But there are a number of differences. Here’s a comparison:

Classes:

• Support inheritance
• Are reference (pointer) types
• The reference can be null
• Have memory overhead per new instance

Structs:

• Do not support inheritance
• Are value types
• Are passed by value (like integers)
• Cannot have a null reference (unless Nullable is used)
• Do not have memory overhead per new instance (unless “boxed”)

9 .

What is the output of the program below?

TestValue : 10

The static constructor of a class is called before any instance of the class is created. The static constructor called here initializes the TestValue variable first. 10 .

At the client side:

Question:

Is there a way to change ClassA so that when the Main method is called, the constructor can be called with parameters without making any new instances of ClassA?

The this keyword is used to call other constructors, to initialize the class object. The following shows the implementation:

What does the following code output?

Decoupling tightly linked classes is possible with dependency injection. This means that classes don’t have to depend on each other directly. There are different ways by which dependency injection can be achived:

• Constructor dependency
• Property dependency
• Method dependency

13 .

Write a C# program that accepts a distance in kilometers, converts it into meters, and then displays the result.

Describe boxing and unboxing. Provide an example.

When you box a value type, it automatically changes to the type object or any interface type that the value type implements. Boxing a value type creates an object instance containing the value and stores it on the heap.

Example:

You’re given a word string containing at least one $ symbol, e.g.:

"foo bar foo $ bar $ foo bar $ "

Question: How do you remove all but the first occurrence of $ from a given string?

This problem has two parts: Preserving the first occurrence and replacing all the others.

We can solve it using a regular expression and String.Replace():

Explanation:

• [^$]*$—Group 1 can handle any number of characters that aren’t $, plus one $ character that has been escaped with a ^.
• (.*)—Group 2 (greedily) captures everything else

With the first occurrence of $ preserved in halves[1]. Value, we can simply use String. Replace() on halves[2]. Without having to use a second regular expression, this value gets rid of all $ characters that are found in the rest of the string.

There is more to interviewing than tricky technical questions, so these are intended merely as a guide. Not every good candidate for the job will be able to answer all of them, and answering all of them doesn’t mean they are a good candidate. At the end of the day, hiring remains an art, a science — and a lot of work.

Tired of interviewing candidates? Not sure what to ask to get you a top hire?

Let Toptal find the best people for you.

Our Exclusive Network of C# Developers

Looking to land a job as a C# Developer?

Let Toptal find the right job for you.

Job Opportunities From Our Network

Submit an interview question

Questions and answers sent in will be looked over and edited by Toptal, LLC, and may or may not be posted, at their sole discretion.

Cliff Quiroga of Sharp Electronics Corporation Interview

FAQ

What questions are asked at the famous brands interview?