String comparison and equality in C Sharp (C#) - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the == operator do when used with strings in C#?

In C#, the == operator compares the contents of two strings to check if they are equal, not just their references. It returns true if the strings have the same characters in the same order.

intermediate

What is the difference between String.Equals() and == for strings?

String.Equals() is a method that compares two strings for equality and can be customized with options like case sensitivity. The == operator also compares string contents but is simpler to use. Both check the actual text, not references.

intermediate

How can you compare two strings ignoring case in C#?

Use String.Equals(str1, str2, StringComparison.OrdinalIgnoreCase) to compare two strings without considering uppercase or lowercase differences.

intermediate

What does String.Compare(str1, str2) return?

It returns an integer: 0 if strings are equal, less than 0 if str1 is less than str2, and greater than 0 if str1 is greater than str2 based on lexicographical order.

advanced

Why should you avoid using ReferenceEquals() to compare strings for equality?

ReferenceEquals() checks if two string variables point to the exact same object in memory, not if their text is the same. This can give false results when strings have the same content but are different objects.

Which operator compares the content of two strings in C#?

A ==

B =

C ===

D !=

The == operator compares the content of two strings for equality in C#.

What does String.Equals(str1, str2, StringComparison.OrdinalIgnoreCase) do?

A Compares strings including case

B Checks if strings are the same object

C Compares strings ignoring case

D Converts strings to uppercase

It compares two strings ignoring case differences.

What value does String.Compare(str1, str2) return if str1 is lexicographically less than str2?

A Less than 0

B 0

C Greater than 0

D Throws an exception

It returns a negative number if str1 is less than str2.

Which method should you use to check if two strings have the same text but ignore case?

A ReferenceEquals()

B String.Equals() with StringComparison.OrdinalIgnoreCase

C == operator

D String.Compare() without parameters

Using String.Equals with StringComparison.OrdinalIgnoreCase ignores case when comparing.

Why is ReferenceEquals() not reliable for string content comparison?

A It compares string lengths only

B It always returns true

C It ignores case differences

D It compares memory addresses, not content

ReferenceEquals checks if two variables point to the same object, not if their text is equal.

Explain how to compare two strings for equality in C# considering case sensitivity.

Think about methods and operators that check string content.

Describe the difference between comparing strings by reference and by content in C#.

Consider what happens when two strings have same text but different memory locations.