C#: Search the position of a substring within a string

Last update on August 25 2025 12:50:39 (UTC/GMT +8 hours)

Write a program in C# Sharp to search for the position of a substring within a string.

C# Sharp Exercises: Search the position of a substring within a string.

Sample Solution:-

C# Sharp Code:

using System;

// Define the Exercise17 class
public class Exercise17
{
    // Main method - entry point of the program
    public static void Main()
    {
        string str1; // Declare a variable to store the main string
        string findstr; // Declare a variable to store the substring to be found

        // Prompt the user to search for a substring within a string
        Console.Write("\n\nSearch the position of a substring within a string :\n");
        Console.Write("-------------------------------------------------------\n");

        // Ask the user to input a string
        Console.Write("Input a String: ");
        str1 = Console.ReadLine();

        // Ask the user to input a substring to be found in the string
        Console.Write("Input a substring to be found in the string: ");
        findstr = Console.ReadLine();

        // Find the index of the substring in the main string
        int index = str1.IndexOf(findstr);

        // Check if the substring is found or not
        if (index < 0)
        {
            Console.WriteLine("The substring was not found in the given string.\n");
        }
        else
        {
            // Display the position/index where the substring was found in the main string
            Console.WriteLine("Found '{0}' in '{1}' at position {2}",
                                findstr, str1, index);
        }
    }
}

Sample Output:

Search the position of a substing within a string :                    
-------------------------------------------------------                
Input a String: Welcome to w3resource.com                              
Input a substring to be found in the string: w3resource                
Found 'w3resource' in 'Welcome to w3resource.com' at position 11

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