C# foreach Tutorials with 3 Different Use Case Examples

The foreach statement in C# iterates through a collection of items such as an array or list, The foreach body must be enclosed in {} braces unless it consists of a single statement.

The code in Listing 1 creates an array of odd numbers and uses foreach loop to loop through the array items and read them.

using System;  
  
class Program  
{  
    static void Main(string[] args)  
    {  
        Console.WriteLine("foreach loop Sample!");  
        int[] oddArray = new int[] { 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21 };  
        foreach (int num in oddArray)  
        {  
            Console.WriteLine(num);  
        }  
        Console.ReadKey();  
    }  
} 

Listing 1.

The output of Listing 1 looks like Figure 1.

 

Figure 1.  

If you’re not familiar with Arrays in C#, please read the article: Arrays Tutorial in C#. 

Listing 2 is an example of for loop that can also be used read an array of items.

for (int counter = 0; counter < oddArray.Length; counter++)  
{  
    Console.WriteLine(oddArray[counter]);  
}

Listing 2.

You can stop and exit a foreach loop by using the break, return, goto, and throw statements. The code snippet in Listing 3 quits execution once the number equals 15. 

using System;  
  
class Program  
{  
    static void Main(string[] args)  
    {  
        Console.WriteLine("foreach loop Sample!");  
        // Array of odd numbers  
        int[] oddArray = new int[] { 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21 };  
        // Loop through array items  
        foreach (int num in oddArray)  
        {  
            Console.WriteLine(num);  
            // Don't read any number after 15  
            if (num == 15) break;  
        }  
        Console.ReadKey();  
    }  
}

Listing 3.

Use foreach to find a char in a string

Remember your early days, when you need to find a character in a string? We can use foreach loop for this to check one character at a time in a string using a foreach, in a loop. Strings are important in any language. Strings in C#

The code snippet in Listing 4 creates an array of chars from a string and reads one character at a time. The code also makes sure that the whitespace between characters is skipped.  

// Read a string - one character at a time and if space, skip it  
string name = "Mahesh Chand Beniwal";  
  
// Convert string into an array of chars  
char[] chArray = name.ToCharArray();  
  
// Loop through chars and display one char at a time  
foreach (char ch in chArray)  
{  
    if (ch.ToString() != " ")  
        Console.WriteLine(ch);  
}

Listing 4. 

Foreach in Collection

Let’s look at another use of the foreach, in a Collection. Do you remember your early programming days when you need to go through a string and find the number of occurrences of a character in a string? The code in Listing 5 does the same using a foreach loop.

// Find number of occurrences of a char in a string  
string str = "A monkey stole a banana, climb on a tree and ate it.";  
char[] chars = str.ToCharArray();  
int ncount = 0;  
// Loop through chars and find all 'n' and count them  
foreach (char ch in chars)  
{  
if (ch == 'n')  
ncount++;  
}  
Console.WriteLine($"Total n found {ncount}");

Listing 5. 

Foreach in Array

Here is another example of using a foreach over an Array. The code snippet in Listing 6 creates an array of strings, and reads and displays each string one at a time.  

// Array of authors - string  
string[] authorList = new string[]  
{ "Mahesh Chand", "Raj Kumar", "Naveen Sharma", "Allen O'neill", "Dave McCarter" };  
// Loop through array and read all authors  
foreach (string author in authorList )  
{  
Console.WriteLine(author);  
}

Listing 6. 

Summary

The foreach, in loop in C# is used to loop through the items in a collection. In this article and code samples, we saw various usage of the foreach with different C# item lists. 

Next reading: The for vs foreach in C#