How to find the Indices of All Occurrences of Substring in C# - Step by Step Examples

How to find the Indices of All Occurrences of Substring in C# ?

Answer

To find the indices of all occurrences of a substring in C#, you can use the IndexOf and LastIndexOf methods in a loop to find all occurrences and store their indices in a list.


✐ Examples

1 Find Indices of All Occurrences in String

In this example,

  1. We create a string variable str with a string value.
  2. We create a list to store indices.
  3. We use a loop with the IndexOf method to find all occurrences of a specific substring within str and store their indices in the list.
  4. We print the list of indices.

C# Program

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        string str = "Hello Hello Hello";
        string substr = "Hello";
        List<int> indices = new List<int>();
        int index = str.IndexOf(substr);
        while (index != -1)
        {
            indices.Add(index);
            index = str.IndexOf(substr, index + 1);
        }
        Console.WriteLine("Indices of all occurrences: " + string.Join(", ", indices));
    }
}

Output

Indices of all occurrences: 0, 6, 12

2 Find Indices of All Occurrences in Another String

In this example,

  1. We create two string variables str1 and str2 with different values.
  2. We create a list to store indices.
  3. We use a loop with the IndexOf method to find all occurrences of str2 within str1 and store their indices in the list.
  4. We print the list of indices.

C# Program

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        string str1 = "apple banana cherry banana";
        string str2 = "banana";
        List<int> indices = new List<int>();
        int index = str1.IndexOf(str2);
        while (index != -1)
        {
            indices.Add(index);
            index = str1.IndexOf(str2, index + 1);
        }
        Console.WriteLine("Indices of all occurrences: " + string.Join(", ", indices));
    }
}

Output

Indices of all occurrences: 6, 20

Summary

In this tutorial, we learned How to find the Indices of All Occurrences of Substring in C# language with well detailed examples.


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