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IndexOf Method of String Explained

IndexOf Method of String

The string IndexOf method is useful to return an index of the first occurrence of the specified character in the given string.

               

Generally, string IndexOf method will start searching for the specified character starting from the Zero position and return the first occurrence of the specified character in the given string.

 

In case, if you want to change the specified character search starting position and to examine the only specified number of character positions in a string, then we can do it by specifying the required start position and number of character positions to search in string IndexOf method.

 

In C#, the string IndexOf() method will perform a case-sensitive search to get the specified character position.

 Syntax of IndexOf Method

Following is the syntax of defining a string IndexOf method to get the specified character position.

 public int IndexOf(char ch)

public int IndexOf(char ch, int startIndex)

public int IndexOf(char ch, int startIndex, int count)

public int IndexOf(char ch, StringComparison comparisonType)

public int IndexOf(string str) 

public int IndexOf(string str, int startIndex)

public int IndexOf(string str, int startIndex, int count)

public int IndexOf(string str, StringComparison comparisonType)

 

If you observe syntaxes, the IndexOf method will return the index position of a specified character or a string in the given string and we can change the starting position of characters search and length of characters to search based on our requirements.

 

The string IndexOf method will return an index position of specified character if that character is found. In case, the specified character is not found, then it will return -1.

 

C# example of IndexOf Method

Following is the example of using the string IndexOf() method to return an index position of a specified character in the given string.

 

using System;

using System.Collections.Generic;

namespace CsharpnaijaTutorial

{

    class Program

    {

        static void Main(string[] args)

        {

            string name = "Musa Sule Gadabs";

            Console.WriteLine($"Character s Index Position: {name.IndexOf("s")}");

            Console.WriteLine($"Ignore Case: {name.IndexOf("s", StringComparison.OrdinalIgnoreCase)}");

            Console.WriteLine($"Change Search Start Position: {name.IndexOf("s", 5)}");

            Console.WriteLine($"Characters Length Reult: {name.IndexOf("s", 5, 3)}");

            Console.WriteLine($"String Position: {name.IndexOf("Sule")}");

            Console.WriteLine("\nPress Enter Key to Exit..");

            Console.ReadLine();

        }

    }

}

 

 

As you see from the above example, we used a IndexOf() method to find the index position of defined character in string “Musa Sule Gadabs” with multiple conditions.

 

When you execute the above C# program, you will get the result as shown below.

 

output window
Output window


 

Thank you

 

References

1.  Tutlane                                                        


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