C# Comparison Operators - Complete Guide
Introduction to Comparison Operators
Comparison operators in C# are used to compare two values and return a boolean result (true or false). These operators are essential for making decisions in your code through conditional statements like if, while, and for loops.
C# provides a comprehensive set of comparison operators that work with various data types, including numeric types, strings, and objects. Understanding how to use these operators correctly is crucial for implementing logic in your programs.
Basic Comparison Operators
C# includes the standard comparison operators for equality and relational comparisons:
Example
using System;
namespace ComparisonOperatorsExample
{
class Program
{
static void Main(string[] args)
{
int a = 10;
int b = 5;
int c = 10;
// Equality operators
Console.WriteLine($"{a} == {c}: {a == c}"); // Equal to
Console.WriteLine($"{a} != {b}: {a != b}"); // Not equal to
// Relational operators
Console.WriteLine($"{a} > {b}: {a > b}"); // Greater than
Console.WriteLine($"{a} < {b}: {a < b}"); // Less than
Console.WriteLine($"{a} >= {c}: {a >= c}"); // Greater than or equal to
Console.WriteLine($"{b} <= {a}: {b <= a}"); // Less than or equal to
// Floating-point comparisons
double x = 0.1 + 0.2;
double y = 0.3;
Console.WriteLine($"\nFloating-point comparison:");
Console.WriteLine($"0.1 + 0.2 = {x}");
Console.WriteLine($"0.3 = {y}");
Console.WriteLine($"x == y: {x == y}"); // False due to floating-point precision
Console.WriteLine($"Math.Abs(x - y) < 0.0001: {Math.Abs(x - y) < 0.0001}"); // True
// Char comparisons (based on Unicode values)
char char1 = 'A';
char char2 = 'B';
char char3 = 'a';
Console.WriteLine($"\nChar comparisons:");
Console.WriteLine($"'A' < 'B': {char1 < char2}"); // True (65 < 66)
Console.WriteLine($"'A' == 'a': {char1 == char3}"); // False (65 != 97)
Console.WriteLine($"'A' < 'a': {char1 < char3}"); // True (65 < 97)
}
}
}Output
10 == 10: True 10 != 5: True 10 > 5: True 10 < 5: False 10 >= 10: True 5 <= 10: True Floating-point comparison: 0.1 + 0.2 = 0.30000000000000004 0.3 = 0.3 x == y: False Math.Abs(x - y) < 0.0001: True Char comparisons: 'A' < 'B': True 'A' == 'a': False 'A' < 'a': True
String Comparison
String comparison in C# requires special attention due to reference vs value semantics:
Example
using System;
namespace StringComparisonExample
{
class Program
{
static void Main(string[] args)
{
string str1 = "hello";
string str2 = "hello";
string str3 = "HELLO";
string str4 = new string(new char[] { 'h', 'e', 'l', 'l', 'o' });
// Equality comparison (== compares string contents)
Console.WriteLine($"str1 == str2: {str1 == str2}"); // True
Console.WriteLine($"str1 == str3: {str1 == str3}"); // False (case different)
Console.WriteLine($"str1 == str4: {str1 == str4}"); // True (same content)
// Reference equality
Console.WriteLine($"ReferenceEquals(str1, str2): {object.ReferenceEquals(str1, str2)}"); // True (interned)
Console.WriteLine($"ReferenceEquals(str1, str4): {object.ReferenceEquals(str1, str4)}"); // False
// String.Equals with options
Console.WriteLine($"str1.Equals(str3): {str1.Equals(str3)}"); // False
Console.WriteLine($"str1.Equals(str3, StringComparison.OrdinalIgnoreCase): {str1.Equals(str3, StringComparison.OrdinalIgnoreCase)}"); // True
// CompareTo method
Console.WriteLine($"'apple'.CompareTo('banana'): {"apple".CompareTo("banana")}"); // -1
Console.WriteLine($"'banana'.CompareTo('apple'): {"banana".CompareTo("apple")}"); // 1
Console.WriteLine($"'apple'.CompareTo('apple'): {"apple".CompareTo("apple")}"); // 0
}
}
}Output
str1 == str2: True
str1 == str3: False
str1 == str4: True
ReferenceEquals(str1, str2): True
ReferenceEquals(str1, str4): False
str1.Equals(str3): False
str1.Equals(str3, StringComparison.OrdinalIgnoreCase): True
'apple'.CompareTo('banana'): -1
'banana'.CompareTo('apple'): 1
'apple'.CompareTo('apple'): 0