Compare two strings lexicographically in C#

The String.Compare() method in C# performs lexicographic (alphabetical) comparison between two strings. It compares strings character by character based on their Unicode values and is case-sensitive by default.

Syntax

Following is the syntax for the basic String.Compare() method −

int result = string.Compare(string1, string2);

For case-insensitive comparison −

int result = string.Compare(string1, string2, true);

Return Value

The String.Compare() method returns an integer value indicating the lexicographic relationship between the two strings −

If str1 is less than str2, it returns -1.
If str1 is equal to str2, it returns 0.
If str1 is greater than str2, it returns 1.

Using Case-Sensitive Comparison

Example

using System;

class Program {
    static void Main(string[] args) {
        string string1 = "amit";
        string string2 = "Amit";
        
        int result = string.Compare(string1, string2);
        
        Console.WriteLine("Comparing '" + string1 + "' with '" + string2 + "'");
        Console.WriteLine("Result: " + result);
        
        if (result < 0)
            Console.WriteLine("'" + string1 + "' comes before '" + string2 + "'");
        else if (result > 0)
            Console.WriteLine("'" + string1 + "' comes after '" + string2 + "'");
        else
            Console.WriteLine("Both strings are equal");
    }
}

The output of the above code is −

Comparing 'amit' with 'Amit'
Result: 1
'amit' comes after 'Amit'

Using Case-Insensitive Comparison

Example

using System;

class Program {
    static void Main(string[] args) {
        string string1 = "apple";
        string string2 = "BANANA";
        
        int caseSensitive = string.Compare(string1, string2);
        int caseInsensitive = string.Compare(string1, string2, true);
        
        Console.WriteLine("Case-sensitive comparison: " + caseSensitive);
        Console.WriteLine("Case-insensitive comparison: " + caseInsensitive);
        
        // Multiple string comparisons
        string[] words = {"zebra", "apple", "Banana", "cherry"};
        Array.Sort(words, string.Compare);
        
        Console.WriteLine("Sorted array:");
        foreach (string word in words) {
            Console.WriteLine(word);
        }
    }
}

The output of the above code is −

Case-sensitive comparison: -1
Case-insensitive comparison: -1
Sorted array:
Banana
apple
cherry
zebra

Comparison with StringComparison Enum

Example

using System;

class Program {
    static void Main(string[] args) {
        string str1 = "Hello";
        string str2 = "hello";
        
        int ordinal = string.Compare(str1, str2, StringComparison.Ordinal);
        int ordinalIgnoreCase = string.Compare(str1, str2, StringComparison.OrdinalIgnoreCase);
        int currentCulture = string.Compare(str1, str2, StringComparison.CurrentCulture);
        
        Console.WriteLine("Ordinal comparison: " + ordinal);
        Console.WriteLine("Ordinal ignore case: " + ordinalIgnoreCase);
        Console.WriteLine("Current culture: " + currentCulture);
    }
}

The output of the above code is −

Ordinal comparison: -1
Ordinal ignore case: 0
Current culture: -1

Comparison Methods

Conclusion

The String.Compare() method provides flexible lexicographic string comparison in C#. Use the basic method for case-sensitive comparison, add a boolean parameter for case-insensitive comparison, or use StringComparison enum for more specific comparison requirements.