Common string methods in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of ToUpper and Trim methods

What is the output of this C# code snippet?

C Sharp (C#)

string text = "  Hello World  ";
string result = text.Trim().ToUpper();
Console.WriteLine(result);

A HELLO WORLD

B DLROW OLLEH

C hello world

D Hello World

💡 Hint

Remember that Trim removes spaces at the start and end, and ToUpper converts all letters to uppercase.

The Trim method removes spaces from both ends of the string, so " Hello World " becomes "Hello World". Then ToUpper converts all letters to uppercase, resulting in "HELLO WORLD".

❓ Predict Output

intermediate

Result of Replace and Substring methods

What will be printed by this C# code?

C Sharp (C#)

string s = "apple pie";
string newS = s.Replace("pie", "tart").Substring(0, 5);
Console.WriteLine(newS);

A tart

B applet

C apple pie

D apple

💡 Hint

Replace changes "pie" to "tart" and Substring(0,5) takes the first 5 characters.

Replace changes "apple pie" to "apple tart". Then Substring(0,5) extracts characters from index 0 to 4, which is "apple".

❓ Predict Output

advanced

Output of IndexOf and Contains methods

What is the output of this code?

C Sharp (C#)

string phrase = "Learning C# is fun!";
int index = phrase.IndexOf("C#");
bool hasFun = phrase.Contains("fun");
Console.WriteLine($"{index} {hasFun}");

A 9 True

B 9 False

C -1 True

D 10 True

💡 Hint

IndexOf returns the first position of the substring or -1 if not found. Contains returns true if substring exists.

The substring "C#" starts at index 9 in the phrase. The phrase contains "fun", so Contains returns true. Output is "9 True".

❓ Predict Output

advanced

Effect of ToLower and StartsWith methods

What does this code print?

C Sharp (C#)

string input = "OpenAI ChatGPT";
string lower = input.ToLower();
bool starts = lower.StartsWith("open");
Console.WriteLine(starts);

A False

B true

C True

D false

💡 Hint

ToLower converts all letters to lowercase. StartsWith checks if string begins with given substring.

After ToLower, the string is "openai chatgpt" which starts with "open". So StartsWith returns true, printed as "True".

❓ Predict Output

expert

Output of complex string manipulation

What is the output of this C# code?

C Sharp (C#)

string s = "  CSharp Programming  ";
string result = s.Trim().Replace(" ", "_").ToLower();
Console.WriteLine(result);

A CSharp_Programming

B csharp programming

C csharp_programming

D CSharp Programming

💡 Hint

Trim removes spaces at ends, Replace changes spaces to underscores, ToLower makes all letters lowercase.

Trim removes spaces at start and end, so "CSharp Programming" remains. Replace changes spaces to underscores: "CSharp_Programming". ToLower converts to "csharp_programming".