String comparison and equality in C Sharp (C#)

Introduction

We compare strings to check if they are the same or to find their order. This helps us decide things like if two words match or which word comes first in a list.

Checking if a user entered the correct password.

Sorting a list of names alphabetically.

Finding if a word exists in a sentence.

Comparing two file names to see if they are identical.

Syntax

C Sharp (C#)

bool result = string1 == string2;
bool resultIgnoreCase = string.Equals(string1, string2, StringComparison.OrdinalIgnoreCase);
int compareResult = string.Compare(string1, string2, StringComparison.Ordinal);

Use == or string.Equals to check if two strings are exactly equal.

Use string.Compare to find which string comes first alphabetically.

Examples

Checks if two strings are exactly the same.

C Sharp (C#)

string a = "hello";
string b = "hello";
bool isEqual = a == b;  // true

Checks equality ignoring uppercase or lowercase differences.

C Sharp (C#)

string a = "Hello";
string b = "hello";
bool isEqualIgnoreCase = string.Equals(a, b, StringComparison.OrdinalIgnoreCase);  // true

Compares two strings alphabetically. Negative means a comes before b.

C Sharp (C#)

string a = "apple";
string b = "banana";
int result = string.Compare(a, b, StringComparison.Ordinal);  // negative number

Sample Program

This program compares two strings in three ways: exact match, ignoring case, and alphabetical order.

C Sharp (C#)

using System;

class Program
{
    static void Main()
    {
        string word1 = "Cat";
        string word2 = "cat";

        bool equalExact = word1 == word2;
        bool equalIgnoreCase = string.Equals(word1, word2, StringComparison.OrdinalIgnoreCase);
        int compareResult = string.Compare(word1, word2, StringComparison.Ordinal);

        Console.WriteLine($"Exact equality: {equalExact}");
        Console.WriteLine($"Equality ignoring case: {equalIgnoreCase}");
        Console.WriteLine($"Compare result: {compareResult}");
    }
}

Important Notes

String comparison is case-sensitive by default.

Use StringComparison.OrdinalIgnoreCase to ignore case differences.

Compare returns 0 if strings are equal, less than 0 if first is before second, and greater than 0 if first is after second.

Summary

Use == or string.Equals to check if strings are equal.

Use string.Compare to find alphabetical order.

Ignore case by using StringComparison.OrdinalIgnoreCase.