How To Compare Strings In C#

Code examples of compare strings in C# using String.Equals, String.Compare, String.CompareTo() method, and StringComparer.

C# String.Compare method compares two strings in C#. You can also use C# String.Equals method and StringComparer class and its method. This article and code examples demonstrate how to compare strings in C# using these different methods.
 
If you're new to strings in C#, I recommend reading Strings In C# Tutorial. You may also want to check out Substrings in C# to learn more about substrings.
 

Using String.Equals

 
The simplest form of comparting two string for the same value is using String.Equals method. If both strings are equal, the method returns true; else returns false.
 
The code sample in Listing 1 is an example of comparing two strings using String.Equals method. 
  1. string author1 = "Mahesh Chand";  
  2. string author2 = "Praveen Kumar";  
  3. string author3 = "Mahesh Chand";  
  4.   
  5. // Compare strings using String.Equals  
  6. if (String.Equals(author1, author2))  
  7.     Console.WriteLine($"{author1} and {author2} have same value.");  
  8. else  
  9.     Console.WriteLine($"{author1} and {author2} are different.");  
  10.   
  11. if (String.Equals(author1, author3))  
  12.     Console.WriteLine($"{author1} and {author3} have same value.");  
  13. else  
  14.     Console.WriteLine($"{author1} and {author3} are different.");  
Listing 1.
 
The output of Listing 1 looks like Figure 1.
 
Compare two strings in C#  
 
Figure 1.
 

Using String.Compare

 
String.Compare method compares two strings and returns an integer value. The return value of the Compare method can be less than zero, greater than zero or equals to zero.
 
Return value Meaning
Less than 0 The first string precedes the second string in the sort order.
0 Both strings are equal in value.
Geater than 0 The first string follows the second string in the sort order.
 
The code sample in Listing 2 is an example of comparing two strings using String.Compare method. 
  1. string author1 = "Mahesh Chand";  
  2. string author2 = "Praveen Kumar";  
  3.   
  4. // Use String.Compare method  
  5. if (String.Compare(author1, author2) == 0)  
  6. Console.WriteLine($"Both strings have same value.");  
  7. else if (String.Compare(author1, author2) < 0)  
  8. Console.WriteLine($"{author1} precedes {author2}.");  
  9. else if (String.Compare(author1, author2) > 0)  
  10. Console.WriteLine($"{author1} follows {author2}.");  
Listing 2.
 

Using CompareTo Method

 
CompareTo method is an instance method of string class. It compares a value (either a string or on object) with a string instance. Return values of this method are same as the Compare method.
 
The code sample in Listing 3 is an example of comparing two strings using the CompareTo method. 
  1. // Use CompareTo method  
  2. if (author1.CompareTo(author2) == 0)  
  3.     Console.WriteLine($"Both strings have same value.");  
  4. else if (author1.CompareTo(author2) < 0)  
  5.     Console.WriteLine($"{author1} precedes {author2}.");  
  6. else if (author1.CompareTo(author2) > 0)  
  7.     Console.WriteLine($"{author1} follows {author2}.");  
Listing 3.
 

Using StringComparer

 
You can also use the StringComparer class to compare two strings. The code sample in Listing 4 is an example of comparing two strings using the StringComparer.Compare method. 
  1. //Use StringComparer  
  2. StringComparer comparer = StringComparer.OrdinalIgnoreCase;  
  3. if (comparer.Compare(author1, author2) == 0)  
  4.     Console.WriteLine($"Both strings have same value.");  
  5. else if (comparer.Compare(author1, author2) < 0)  
  6.     Console.WriteLine($"{author1} precedes {author2}.");  
  7. else if (comparer.Compare(author1, author2) > 0)  
  8.     Console.WriteLine($"{author1} follows {author2}.");  
Listing 4.
 

Complete Code Example

 
Listing 5 is the complete program written in .NET Core and C#.  
  1. using System;  
  2.   
  3. namespace StringComapreSample  
  4. {  
  5.     class Program  
  6.     {  
  7.         static void Main(string[] args)  
  8.         {  
  9.                 string author1 = "Mahesh Chand";  
  10.                 string author2 = "Praveen Kumar";  
  11.                 string author3 = "Mahesh Chand";  
  12.   
  13.                 // Compare strings using String.Equals  
  14.                 if (String.Equals(author1, author2))  
  15.                     Console.WriteLine($"{author1} and {author2} have same value.");  
  16.                 else  
  17.                     Console.WriteLine($"{author1} and {author2} are different.");  
  18.   
  19.                 if (String.Equals(author1, author3))  
  20.                     Console.WriteLine($"{author1} and {author3} have same value.");  
  21.                 else  
  22.                     Console.WriteLine($"{author1} and {author3} are different.");  
  23.   
  24.   
  25.             // Use String.Compare method  
  26.             if (String.Compare(author1, author2) == 0)  
  27.                 Console.WriteLine($"Both strings have same value.");  
  28.             else if (String.Compare(author1, author2) < 0)  
  29.                 Console.WriteLine($"{author1} precedes {author2}.");  
  30.             else if (String.Compare(author1, author2) > 0)  
  31.                 Console.WriteLine($"{author1} follows {author2}.");  
  32.   
  33.             // Use CompareTo method  
  34.             if (author1.CompareTo(author2) == 0)  
  35.                 Console.WriteLine($"Both strings have same value.");  
  36.             else if (author1.CompareTo(author2) < 0)  
  37.                 Console.WriteLine($"{author1} precedes {author2}.");  
  38.             else if (author1.CompareTo(author2) > 0)  
  39.                 Console.WriteLine($"{author1} follows {author2}.");  
  40.   
  41.             //Use StringComparer  
  42.             StringComparer comparer = StringComparer.OrdinalIgnoreCase;  
  43.             if (comparer.Compare(author1, author2) == 0)  
  44.                 Console.WriteLine($"Both strings have same value.");  
  45.             else if (comparer.Compare(author1, author2) < 0)  
  46.                 Console.WriteLine($"{author1} precedes {author2}.");  
  47.             else if (comparer.Compare(author1, author2) > 0)  
  48.                 Console.WriteLine($"{author1} follows {author2}.");
  49.             Console.ReadKey();  
  50.         }  
  51.     }  
  52. }  
Listing 5.
 

Summary

 
This article and code sample demonstrated how to comapre two strings in C# and .NET Core using different methods.