C# program to check if a Substring is present in a Given String

The Contains() method in C# is used to check if a substring is present within a given string. It returns a boolean value − true if the substring is found, and false otherwise.

Syntax

Following is the syntax for the Contains() method −

bool result = string.Contains(substring);

Parameters

• substring − The string to search for within the main string.

Return Value

The Contains()bool value −

• true − if the substring is found in the main string

• false − if the substring is not found

Using Contains() Method

Example 1: Basic Substring Check

The following example demonstrates how to check if "Uni" is present in the string "United" −

using System;

public class Demo {
   public static void Main() {
      string str1 = "United", str2 = "Uni";
      bool res;
      res = str1.Contains(str2);
      if (res)
         Console.WriteLine("The substring '" + str2 + "' is in the string '" + str1 + "'");
      else
         Console.WriteLine("The substring '" + str2 + "' is not in the string '" + str1 + "'");
   }
}

The output of the above code is −

The substring 'Uni' is in the string 'United'

Example 2: Case-Sensitive Search

The Contains() method is case-sensitive by default −

using System;

public class CaseSensitiveDemo {
   public static void Main() {
      string mainString = "Programming";
      string substring1 = "gram";
      string substring2 = "GRAM";
      
      Console.WriteLine("Main string: " + mainString);
      Console.WriteLine("Searching for 'gram': " + mainString.Contains(substring1));
      Console.WriteLine("Searching for 'GRAM': " + mainString.Contains(substring2));
   }
}

The output of the above code is −

Main string: Programming
Searching for 'gram': True
Searching for 'GRAM': False

Example 3: Case-Insensitive Search

For case-insensitive searches, use the StringComparison.OrdinalIgnoreCase parameter −

using System;

public class CaseInsensitiveDemo {
   public static void Main() {
      string mainString = "Programming";
      string substring = "GRAM";
      
      bool caseSensitive = mainString.Contains(substring);
      bool caseInsensitive = mainString.Contains(substring, StringComparison.OrdinalIgnoreCase);
      
      Console.WriteLine("Main string: " + mainString);
      Console.WriteLine("Case-sensitive search for 'GRAM': " + caseSensitive);
      Console.WriteLine("Case-insensitive search for 'GRAM': " + caseInsensitive);
   }
}

The output of the above code is −

Main string: Programming
Case-sensitive search for 'GRAM': False
Case-insensitive search for 'GRAM': True

Conclusion

The Contains() method provides a simple and efficient way to check if a substring exists within a string in C#. Remember that it is case-sensitive by default, but you can perform case-insensitive searches using the StringComparison.OrdinalIgnoreCase parameter.