Strings

Question 1

Check if string s is null or empty.

Answer 1

string.IsNullOrEmpty(s);

Question 2

Class that represents a mutable string of characters.

Answer 2

StringBuilder

Question 3

Convert string s into char array.

Answer 3

s.ToCharArray();

Question 4

Length of a string s.

Answer 4

s.Length;

Question 5

Swap t[0] and t[1] with tuple deconstruction and assignment.

Answer 5

(t[0],t[1])=(t[1],t[0]);

Question 6

Create string from table of chars named characters.

Answer 6

new string(characters);

Question 7

Reverse array tab in one line.

Answer 7

Array.Reverse(tab);

Question 8

What will happen in this code (the method has parameter of type string):
SomeGetByStringMethod(null);

Answer 8

No error.

Question 9

What will happen in this code:
object obj = null;
SomeGetByStringMethod(obj);

Answer 9

Compilation error.

Question 10

What will happen in this code:
typeof(Program).GetMethod(“SomeGetByStringMethod”).Invoke(null, new object[] { 123 });

Answer 10

Runtime error.

Question 11

What will happen in this code:
typeof(Program).GetMethod(“TEST”).Invoke(null, new object[] { “abc” });

Answer 11

No error.

Question 12

What will happen in this code (the method has parameter of type string):
SomeGetByStringMethod(123);

Answer 12

Compilation error.

Question 13

Create “Hello, <name>!" string with string interpolation, where name is the variable.</name>

Answer 13

$”Hello, {name}”;

Question 14

Check if string s is null or white space.

Answer 14

string.IsNullOrWhiteSpace(s);

Question 15

Compare strings a and b case sensitive.

Answer 15

a == b;

Question 16

Compare strings a and b case insensitive.

Answer 16

string.Equals(a,b,StringComparison.OrdinalIgnoreCase);

Question 17

What is the comparison method that will return numerical value based on strings a and b?

Answer 17

string.Compare(a,b,StringComparison.OrdinalIgnoreCase);

Question 18

How to check if
string sentence = “The quick brown fox”;
has a word “brown” in it?

Answer 18

sentence.Contains(“brown”);

Question 19

How to check if
string sentence = “The quick brown fox”;
has a word “The” at the beginning?

Answer 19

sentence.StartsWith(“The”);

Question 20

How to check if
string sentence = “The quick brown fox”;
has a word “fox” at the end?

Answer 20

sentence.EndsWith(“fox”);

Question 21

How to check in
string sentence = “The quick brown fox”;
the index that word “quick” starts in?

Answer 21

sentence.IndexOf(“quick”);

Question 22

How to check in
string sentence = “The quick brown fox”;
the last index of a letter ‘o’?

Answer 22

sentence.LastIndexOf(“o”);

Question 23

How to retrieve word “quick” from the sentence “The quick brown fox”?

Answer 23

sentence.Substring(4,5);

Question 24

How to replace word “fox” with “dog” in the sentence “The quick brown fox”?

Answer 24

sentence.Replace(“fox”,”dog”);

Question 25

How to add word "very" to the sentence "The quick brown fox"?

Answer 25

sentence.Insert(4,"very");

Question 26

How to remove word "quick" from the sentence "The quick brown fox"?

Answer 26

sentence.Remove(4,6);

Question 27

How to get rid of white spaces in string s = " Hello "; ?

Answer 27

s.Trim();

Question 28

How to get rid of white spaces at the beginning of string s = " Hello "; ?

Answer 28

s.TrimStart();

Question 29

How to get rid of white spaces at the end of string s = " Hello "; ?

Answer 29

s.TrimEnd();

Question 30

How to get fruits from this string s="apple,banana,cherry";?

Answer 30

string[] fruits=s.Split(',');

Question 31

How to get this table elements: string[] s = ["apple","banana","cherry"]; into "apple - banana - cherry"?

Answer 31

string.Join(" - ",s);

Question 32

How to make all characters in string s="hello"; big?

Answer 32

s.ToUpper();

Question 33

How to make all characters in string s="Hello"; small?

Answer 33

s.ToLower();

Question 34

How to add age value into this sentence "The age is ..." with standard formatting?

Answer 34

string.Format("The age is {0}",age);

Question 35

How to add a word "world" into below sb? StringBuilder sb = new StringBuilder("Hello");

Answer 35

sb.Append(" world");

Question 36

How to add a comma into below sb? StringBuilder sb = new StringBuilder("Hello world");

Answer 36

sb.Insert(5,",");

Question 37

How to replace "world" with "C#" in below sb? StringBuilder sb = new StringBuilder("Hello world");

Answer 37

sb.Replace("world","C#");

Question 38

How to create string from below sb? StringBuilder sb = new StringBuilder("Hello world");

Answer 38

sb.ToString();

Question 39

How to convert string 123 to number?

Answer 39

int.Parse("123");

Question 40

How to convert string 123 to a number safe? Save it as newNb.

Answer 40

int.TryParse("123",out newNb);

Question 41

Convert number a=123 to a string.

Answer 41

a.ToString();

Question 42

Convert below date to string in EU format: DateTime date = DateTime.Now;

Answer 42

date.ToString("yyyy-MM-dd")

Question 43

Convert 2024-02-17 string to date.

Answer 43

DateTime.Parse("2024-02-17");

Question 44

Check string s for null and return "default" if it is null.

Answer 44

return input ?? "default;