How To Validate Email ID in C#?

Validating email addresses is a common task in C# applications, especially when dealing with user input or processing email-related functionality. It is very important to validate an Email ID before storing it in our database.


All Email IDs must follow a specific format and must belong to some domain. Here in this article, we are going to cover three different methods that we can use for email validation. 


Email Format Validation.

In C# we can validate an Email ID using the below methods:

  • Using Regular Expression.
  • Using Built-in Library Function.
  • Using Custom Validation.

Let's understand each of these methods in detail with C-sharp Code.


Method 1: Using Regular Expression.

Using a regular expression is a robust way to validate email addresses. It allows you to define complex patterns that match valid email formats.


C# Example Code:

// C#-sharp code to validate email id using Regular Expression
using System;
using System.Text.RegularExpressions;

class EmailValidator
{
    public static bool IsValidEmail(string email)
    {
        // Define a regular expression pattern for valid email addresses
        string pattern = @"^[\w-]+(\.[\w-]+)*@([\w-]+\.)+[a-zA-Z]{2,7}$";

        // Use Regex.IsMatch to check if the email matches the pattern
        return Regex.IsMatch(email, pattern);
    }

    static void Main()
    {
        string email = "example@email.com";
        bool isValid = IsValidEmail(email);
        
        Console.WriteLine($"Is {email} a valid email address? {isValid}");
    }
}
Output:
Is example@email.com a valid email address? True

Explanation of Above C# Code:
  • We define a regular expression pattern that describes valid email addresses.
  • The pattern ^[\w-]+(\.[\w-]+)*@([\w-]+\.)+[a-zA-Z]{2,7}$ checks for common email format rules.
  • Regex.IsMatch(email, pattern) tests if the email string matches the pattern.
  • The IsValidEmail method returns true if the email is valid.

Method 2: Using Regular Expression.

C# also provides a built-in library, System.Net.Mail, for email-related tasks, including email address validation.

C# Example Code:

// C#-sharp code to validate email id using Built-in Library
using System;
using System.Net.Mail;

class EmailValidator
{
    public static bool IsValidEmail(string email)
    {
        try
        {
            var mailAddress = new MailAddress(email);
            return true;
        }
        catch (FormatException)
        {
            return false;
        }
    }

    static void Main()
    {
        string email = "algolesson@email.com";
        bool isValid = IsValidEmail(email);
        
        Console.WriteLine($"Is {email} a valid email address? {isValid}");
    }
}
Output:
Is algolesson@email.com a valid email address? True

Explanation of Above C# Code:
  • We create a MailAddress object with the given email string.
  • If the email string is not a valid email address, a FormatException is thrown.
  • We catch the exception and return false for invalid emails.

Method 3: Using Custom Validation.

For basic validation without using regular expressions or libraries, you can implement a simple custom validation method.

C# Example Code:

// C#-sharp code to validate email id using Custom Validation
using System;

class EmailValidator
{
    public static bool IsValidEmail(string email)
    {
        if (string.IsNullOrWhiteSpace(email))
            return false;

        if (!email.Contains("@") || !email.Contains("."))
            return false;

        // Additional checks can be added based on your requirements
        
        return true;
    }

    static void Main()
    {
        string email = "algolesson@email.com";
        bool isValid = IsValidEmail(email);
        
        Console.WriteLine($"Is {email} a valid email address? {isValid}");
    }
}
Output:
Is algolesson@email.com a valid email address? True

Explanation of Above C# Code:
  • We perform basic checks like ensuring the email is not null or empty and contains both "@" and ".".
  • You can add additional checks based on your specific requirements.

So these are a few methods that you can use to validate your email id in C# choose any one of them that is best for you according to your use and requirement.

C# Program to Formats Data and Time Value.

Date and time values are crucial in applications for various purposes, such as displaying timestamps, scheduling events, or formatting data for reports. In C#, the DateTime structure is used to work with date and time values. You can format these values into human-readable strings using the ToString method.


The format string used with the DateTime.ToString method allows you to customize how the date and time are displayed. Here we are going to look at some examples of format strings and the resulting formatted date and time:


1. "yyyy-MM-dd HH:mm:ss": This format string displays the date and time in the format "Year-Month-Day Hour:Minute:Second."

C# Code:

// C-sharp program to print current date and time
using System;

public class HelloWorld
{
    public static void Main(string[] args)
    {
        DateTime dateTime = DateTime.Now;
        string formattedDateTime = dateTime.ToString("yyyy-MM-dd HH:mm:ss");
        Console.WriteLine(formattedDateTime);
    }
}
Output:
2023-09-02 14:46:04

2. "dd/MM/yyyy": This format string displays the date in the format "Day/Month/Year."

C# Code:

// C-sharp program to print current date and time
using System;

public class HelloWorld
{
    public static void Main(string[] args)
    {
        DateTime dateTime = DateTime.Now;
        string formattedDateTime = dateTime.ToString("dd/MM/yyyy");
        Console.WriteLine(formattedDateTime);
    }
}
Output:
25/09/2023

3. "MMMM dd, yyyy": This format string displays the date as "Month Day, Year."

C# Code:

// C-sharp program to print current date and time
using System;

public class HelloWorld
{
    public static void Main(string[] args)
    {
        DateTime dateTime = DateTime.Now;
        string formattedDateTime = dateTime.ToString("MMM dd, yyyy");
        Console.WriteLine(formattedDateTime);
    }
}
Output:
July 24, 2023

4. "hh:mm tt": This format string displays the time in a 12-hour clock format with "AM" or "PM."

C# Code:

// C-sharp program to print current date and time
using System;

public class HelloWorld
{
    public static void Main(string[] args)
    {
        DateTime dateTime = DateTime.Now;
        string formattedDateTime = dateTime.ToString("hh:mm tt");
        Console.WriteLine(formattedDateTime);
    }
}
Output:
04:40 PM

I hope you get some idea about how to get date and time values in the C# programming language. There are many different ways to customize and format the Date and Time value.

Basic Format Specifiers.

Below is the list of some commonly used Format Specifiers:
  • "d": Short date pattern (e.g., "7/25/2023").
  • "D": Long date pattern (e.g., "Monday, July 25, 2023").
  • "t": Short time pattern (e.g., "3:30 PM").
  • "T": Long time pattern (e.g., "3:30:45 PM").
  • "f": Full date and short time pattern (e.g., "Monday, July 25, 2023 3:30 PM").
  • "F": Full date and long time pattern (e.g., "Monday, July 25, 2023 3:30:45 PM").
  • "g": General date and short time pattern (e.g., "7/25/2023 3:30 PM").
  • "G": General date and long time pattern (e.g., "7/25/2023 3:30:45 PM").
  • "yyyy-MM-dd": Custom date format (e.g., "2023-07-25").
  • "HH:mm:ss": Custom time format (e.g., "15:30:45").

Custom Format Specifiers.

In addition to the predefined format specifiers, you can create custom format strings. Here's how to use some common custom specifiers:
  • "yyyy": Four-digit year (e.g., "2023").
  • "MM": Two-digit month (e.g., "07" for July).
  • "dd": Two-digit day (e.g., "25").
  • "HH": Two-digit hour (24-hour clock, e.g., "15").
  • "hh": Two-digit hour (12-hour clock, e.g., "03").
  • "mm": Two-digit minute (e.g., "30").
  • "ss": Two-digit second (e.g., "45").
  • "fff": Milliseconds (e.g., "123").

C# Code to Customize Data and Time Format.

// C-sharp program to customize current date and time
using System;

public class HelloWorld
{
    public static void Main(string[] args)
    {
        DateTime now = DateTime.Now;
        
        // "7/25/2023"
        string shortDate = now.ToString("d"); 
        // "Monday, July 25, 2023"
        string longDate = now.ToString("D"); 
        // "3:30 PM"
        string shortTime = now.ToString("t");
        // "3:30:45 PM"
        string longTime = now.ToString("T");
        // "Monday, July 25, 2023 3:30"
        string fullDateTime = now.ToString("F");
        // "2023-07-25 15:30:45"
        string customFormat = now.ToString("yyyy-MM-dd HH:mm:ss"); 
        
        Console.WriteLine(shortDate);
        Console.WriteLine(longDate);
        Console.WriteLine(shortTime);
        Console.WriteLine(longTime);
        Console.WriteLine(fullDateTime);
        Console.WriteLine(customFormat);
    }
}
Output:
09/02/2023
Saturday, 02 September 2023
15:22
15:22:07
Saturday, 02 September 2023 15:22:07
2023-09-02 15:22:07

Formatting date and time values in C# is essential for displaying information to users or storing timestamps in a specific format. By using format specifiers, you can control how date and time values are presented. Understanding the available format options and creating custom formats when necessary will help you work effectively with date and time values in your C# applications.

C# Program to Find Fibonacci Series.

Problem Statement: Write a C# program to generate a Fibonacci series of n terms. The program should display the first n numbers in the Fibonacci sequence.

Example:

Input: n = 10
Output: 
Fibonacci Series of 10 terms:
0 1 1 2 3 5 8 13 21 34

Steps to Print Fibonacci Series.

Below are steps that you need to follow to print a Fibonacci series in C# Sharp:

Step 1: Take an integer n as input, which represents the number of terms in the Fibonacci series.
Step 2: Initialize three variables: firstTerm and secondTerm to 0 and 1 (the initial terms of the Fibonacci sequence), and nextTerm to 0 (to hold the next term to be calculated).
Step 3: Display a header message, such as "Fibonacci Series of n terms."
Step 4: Use a for loop to generate the Fibonacci series. Start the loop from 0 and iterate n times.
Step 5: In each iteration of the loop, calculate the nextTerm as the sum of firstTerm and secondTerm.
Step 6: Update firstTerm and secondTerm to prepare for the next iteration. Set firstTerm to the value of secondTerm, and secondTerm to the value of nextTerm.

Step 7: Display the nextTerm as the current term in the Fibonacci sequence.

C# Sharp Code to Print Fibonacci Series.

// C-sharp code to print Fibonacci Series
using System;

namespace FibonacciSeries
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.Write("Enter the number of terms: ");
            int n = Convert.ToInt32(Console.ReadLine());

            int firstTerm = 0, secondTerm = 1, nextTerm;

            Console.WriteLine($"Fibonacci Series of {n} terms:");
            for (int i = 0; i < n; i++)
            {
                if (i <= 1)
                    nextTerm = i;
                else
                {
                    nextTerm = firstTerm + secondTerm;
                    firstTerm = secondTerm;
                    secondTerm = nextTerm;
                }
                Console.Write(nextTerm + " ");
            }
        }
    }
}
Output:
Enter the number of terms: 8
Fibonacci Series of 8 terms:
0 1 1 2 3 5 8 13 

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C# Program to Generate a Multiplication Table for a Given Number.

Problem Statement: Write a C# program to generate a multiplication table for a given number n. The table should display the products of n multiplied by numbers from 1 to 10.

Example:

Input: n = 5
Output:
Multiplication Table for 5:
5 x 1 = 5
5 x 2 = 10
5 x 3 = 15
5 x 4 = 20
5 x 5 = 25
5 x 6 = 30
5 x 7 = 35
5 x 8 = 40
5 x 9 = 45
5 x 10 = 50

Steps to Solve the Problem:

Below are the steps that you need to follow to print a multiplication table of any given number:

Step 1: Take an integer n as input, which represents the number for which the multiplication table needs to be generated.
Step 2: Display a header message, such as "Multiplication Table for n."
Step 3: Use a for loop to iterate through numbers from 1 to 10.
Step 4: In each iteration of the loop, calculate the product of n multiplied by the current loop variable.
Step 5: Display the multiplication equation, including n, the current loop variable, and the product.

C# Code Implementation for Multiplication Table.

// C-sharp code to print multiplication table
using System;

namespace MultiplicationTable
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.Write("Enter a number: ");
            int n = Convert.ToInt32(Console.ReadLine());

            Console.WriteLine($"Multiplication Table for {n}:");
            for (int i = 1; i <= 10; i++)
            {
                int product = n * i;
                Console.WriteLine($"{n} x {i} = {product}");
            }
        }
    }
}
Output:
Enter a number: 8
Multiplication Table for 8:
8 x 1 = 8
8 x 2 = 16
8 x 3 = 24
8 x 4 = 32
8 x 5 = 40
8 x 6 = 48
8 x 7 = 56
8 x 8 = 64
8 x 9 = 72
8 x 10 = 80

Explanation:

The above program uses a for loop to generate the multiplication table for the given number. The loop iterates from 1 to 10, calculating the product in each iteration.

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C# Program to Calculate Sum of Natural Numbers.

Calculating the sum of natural numbers is a fundamental problem in programming. It involves adding up numbers from 1 to a given positive integer. In this article, we will walk through the process of solving this problem using C# and provide a detailed step-by-step guide.


Problem Statement: Write a C# program to calculate the sum of natural numbers up to a given positive integer n.

Example:

Input: n = 5
Output: 15

Explanation:
The sum of Natural Number from 1 to 5 is 15.

Steps to Find Sum of Natural Numbers.

Below are the steps that you need to follow to solve this problem:

Step 1: Take an integer n as input, which represents the upper limit of the natural numbers.
Step 2: Declare a variable sum and set it to 0. This variable will be used to store the sum of the natural numbers.
Step 3: Use a for loop to iterate through numbers from 1 to n.
Step 4: In each iteration of the loop, add the current number to the sum variable.
Step 5: After the loop completes, output the value of the sum variable as the sum of natural numbers from 1 to n.

C# Code to Find Sum of Natural Numbers Using Loop.

// C# code to find the sum of natural numbers
using System;

namespace SumOfNaturalNumbers
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.Write("Enter a positive integer: ");
            int n = Convert.ToInt32(Console.ReadLine());

            int sum = 0;
            for (int i = 1; i <= n; i++)
            {
                sum += i;
            }

            Console.WriteLine($"Sum of natural numbers from 1 to {n} is {sum}");
        }
    }
}
Output:
Enter a positive integer: 6
Sum of natural numbers from 1 to 6 is 21

C# Code to Find Sum Natural Number Using Formula.

We can also find the sum of n natural numbers using the formula sum = n * (n + 1) / 2.
// C# code to find the sum of natural numbers
using System;

namespace SumOfNaturalNumbers
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.Write("Enter a positive integer: ");
            int n = Convert.ToInt32(Console.ReadLine());

            int sum = 0;
            //formula to calculate sum of natural numbers
            sum = n * (n + 1) / 2;

            Console.WriteLine($"Sum of natural numbers from 1 to {n} is {sum}");
        }
    }
}
Output:
Enter a positive integer: 5
Sum of natural numbers from 1 to 5 is 15

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How To Resolve Collison in Hash Table in C++.

In hash table implementations, collisions occur when two different keys hash to the same index in the array. To handle collisions, various strategies are employed to ensure efficient storage and retrieval of data. In this article, we'll explore some common methods to resolve collisions and provide working examples in C++.


Collision Resolution Methods in Hash Table.

There are multiple ways to resolve collision in Hash Table (Hash Map) but here we are going to learn about three popular collision resolution methods mentioned below:

Now let's discuss each of these methods one by one in detail and use them in Hash Table Implementation.


Method 1: Chaining (Separate Chaining)

Separate Chaining is a popular collision resolution technique used in hash table implementations. It involves maintaining a linked list at each hash table index to handle collisions.


How does Separate Chaining Work?

It involves four important steps to implement the Chaining method to resolve collision:

1. Initialization: Create an array of linked lists, where each list represents a bucket in the hash table.


2. Insertion: When inserting a key-value pair, compute the hash of the key and determine the index in the array. Add the key-value pair to the linked list at that index.


3. Search: To retrieve a value for a given key, calculate the hash to find the index, and then search the linked list at that index for the key.


4. Collision Handling: When multiple keys hash to the same index (collision), they are simply added to the same linked list at that index.


Implementation of Separate Chaining in C++.

// C++ code for the implementation of Chaining in Hash Table
#include <iostream>
#include <list>
#include <utility>

class HashTable {
private:
    static const int tableSize = 10;
    std::list<std::pair<int, int>> table[tableSize];

    int hashFunction(int key) {
        return key % tableSize;
    }

public:
    void insert(int key, int value) {
        int index = hashFunction(key);
        table[index].emplace_back(key, value);
    }

    int get(int key) {
        int index = hashFunction(key);
        for (const auto& pair : table[index]) {
            if (pair.first == key) {
                return pair.second;
            }
        }
        return -1; // Key not found
    }
};

int main() {
    HashTable hashTable;

    hashTable.insert(5, 50);
    hashTable.insert(15, 150);
    hashTable.insert(25, 250);
 
    std::cout << "Value at key 15: " << hashTable.get(15) << std::endl;

    return 0;
}
Output:
Value at key 15: 150

Method 1: Open Addressing.

Open Addressing is another widely used collision resolution technique in hash table implementations. Unlike Separate Chaining, Open Addressing aims to resolve collisions by placing the collided element directly into the hash table itself.

How Open Addressing Works?

It involves four important steps to implement the Open Address method to resolve collision:

1. Initialization: Create an array (hash table) to hold the key-value pairs. Initially, all slots are empty.

2. Insertion: When inserting a key-value pair, compute the hash of the key and determine the index in the array. If the slot is occupied, use a probing sequence (linear, quadratic, etc.) to find the next available slot.

3. Search: To retrieve a value for a given key, calculate the hash to find the index, and then use the same probing sequence to search for the key.

4. Collision Handling: When a collision occurs, Open Addressing attempts to find the next available slot within the array to place the collided element.

Implementation of Open Addressing in C++.

// C++ code to implement Open Addression in Hash Map
#include <iostream>
#include <vector>
using namespace std;

class HashTable {
private:
    static const int tableSize = 10;
    vector<pair<int, int>> table;

    int hashFunction(int key) {
        return key % tableSize;
    }

    int linearProbing(int index, int attempt) {
        return (index + attempt) % tableSize;
    }

public:
    HashTable() : table(tableSize, std::make_pair(-1, -1)) {}

    void insert(int key, int value) {
        int index = hashFunction(key);
        int attempt = 0;

        while (table[index].first != -1) {
            index = linearProbing(index, ++attempt);
        }

        table[index] = make_pair(key, value);
    }

    int get(int key) {
        int index = hashFunction(key);
        int attempt = 0;

        while (table[index].first != -1) {
            if (table[index].first == key) {
                return table[index].second;
            }
            index = linearProbing(index, ++attempt);
        }

        return -1; // Key not found
    }
};

int main() {
    HashTable hashTable;

    hashTable.insert(5, 50);
    hashTable.insert(15, 150);
    hashTable.insert(25, 250);

    cout << "Value at key 15: " << hashTable.get(15) << endl;

    return 0;
}
Output:
Value at key 15: 150

Method 3: Robin Hood Hashing.

Robin Hood Hashing is a variant of Open Addressing, a collision resolution technique used in hash tables. It focuses on distributing collided elements more evenly within the table to achieve better performance.

How Robin Hood Hashing Works?

It involves four important steps to implement the Robin Hood Hashing method to resolve collision:

1. Initialization: Create an array (hash table) to hold the key-value pairs. Initially, all slots are empty.

2. Insertion: When inserting a key-value pair, calculate the hash of the key and determine the index in the array. If the slot is occupied, compare the distances between the desired index and the current index for both the existing element and the new element. If the new element's distance is smaller, swap the elements and continue probing.

3. Search: To retrieve a value for a given key, calculate the hash to find the index, and then use the same probing sequence to search for the key.

4. Collision Handling: Robin Hood Hashing aims to minimize the difference in the probing distances, ensuring a more balanced distribution of elements.

Implementation of Robin Hood Hashing in C++.

// C++ code to implement Robin Hood Hashing
#include <iostream>
#include <vector>
using namespace std;

class HashTable {
private:
    static const int tableSize = 10;
    vector<pair<int, int>> table;

    int hashFunction(int key) {
        return key % tableSize;
    }

public:
    HashTable() : table(tableSize, make_pair(-1, -1)) {}

    void insert(int key, int value) {
        int index = hashFunction(key);
        int distance = 0;

        while (table[index].first != -1) {
            if (distance > tableSize - 1) {
                break; // Avoid infinite loop
            }

            if (distance > index - hashFunction(table[index].first)) {
                swap(key, table[index].first);
                swap(value, table[index].second);
                distance = index - hashFunction(key);
            }

            index = (index + 1) % tableSize;
            distance++;
        }

        table[index] = make_pair(key, value);
    }

    int get(int key) {
        int index = hashFunction(key);
        int distance = 0;

        while (table[index].first != -1) {
            if (table[index].first == key) {
                return table[index].second;
            }
            index = (index + 1) % tableSize;
            distance++;
        }

        return -1; // Key not found
    }
};

int main() {
    HashTable hashTable;

    hashTable.insert(5, 50);
    hashTable.insert(15, 150);
    hashTable.insert(25, 250);

    cout << "Value at key 15: " << hashTable.get(15) << endl;

    return 0;
}
Output:
Value at key 15: 150

Conclusion:

Collision resolution is a critical aspect of hash table implementations. Chaining is a popular method using linked lists to store colliding elements. This ensures efficient storage and retrieval while keeping collision-related complexities under control. In more advanced implementations, other methods like open addressing and Robin Hood hashing are explored to further optimize hash table performance.

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