C#

Understanding DateTime in C#

The DateTime type in C# is used for working with dates and times. It represents an instant in time used for tasks such as logging events, scheduling tasks, or measuring durations. For instance:

In this example we are retrieving the current date and time on the system running the code.We can use DateTime for formatting, comparisons, or arithmetic operations.

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Considering Time Zones in DateTime

While  using DateTime in real-world applications we may require considering the user’s time zone to ensure accurate scheduling, communication, or logging. For example, if you’re building an international application, the server may use UTC, but you’ll need to display the local time for your users. Ignoring time zones can lead to wrong datetime values.

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Handling Time Zones in C#

To consider time zones, you can use the TimeZoneInfo class, which provides methods for conversions:

Here, DateTime.UtcNow retrieves the current time in UTC, while TimeZoneInfo.Local adjusts it to the user’s machine time zone.

By combining DateTime and TimeZoneInfo, we can handle time zone-sensitive scenarios, ensuring that our application delivers accurate and user-friendly results.

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As.NET developers, often we work with data from various sources. Suppose you are working on some HR application where you have some employee IDs within your database list and employee information coming through some API. Now you want to find out whether data from this API contains some of the employees in your database or not. In such a scenario we need to combine data from multiple sources.

Matching Elements in Two Lists in C#

To implement this, we can loop through the list of employees and check if any employee’s `Id` is matching with any of the IDs in the list of Ids We can convert the string list into a set for fast lookups: If found – return the corresponding Employee object; otherwise return null.

public class Employee
{
public string FirstName { get; set; }
public string LastName { get; set; }
public int Id { get; set; }
}

//Search Employee by Id in a list
public class FindEmployee
{
public static Employee? FindMatchingEmployee(List<string> listOfEmployeeIds, List<Employee> listOfEmployees)
{
// Convert string list to a HashSet for faster lookups
HashSet<int> employeeIdsSet = listOfEmployeeIds.Select(id => int.Parse(id)).ToHashSet();

// Iterate through the employee list
foreach (var employee in listOfEmployees)
{
if (employeeIdsSet.Contains(employee.Id))
{
return employee; // Return the matching employee
}
}

return null; // Return null if not found
}
}

 

Following is the above implementation step by step:

1. Define the Employee Class: The Employee class has three properties: FirstName,LastName, and Id. These represent the details of each employee.
2. Convert the String List to a HashSet: The list of employee IDs (as strings) is converted to a HashSet<int> after parsing each string to an integer. The HashSet provides faster lookup times for comparison.
3. Iterate Through the Employees: Loop through each Employee object in the listOfEmployees to check if its Id is present in the HashSet of IDs.
4. Return the Result:
If a match is found, return the Employee object.
If no match is found after the loop, return null
5. Usage of the Method: Call this method by passing `listOfEmployeeIds` and `listOfEmployees` to find a matching employee or confirm that no matches exist.

This approach ensures readability and efficiency, making it suitable for scenarios where performance and clarity are both essential.

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Some numbers are considered special because of their unique properties. One type of special number is called a Prime number.We will first understand what is a prime number and then write a small program in C# that can check if a number is prime or not.

What is a Prime Number?

A prime number is a special number that can only be divided evenly by 1 and itself. That means if you try to divide it by any other number, you’ll receive a remainder. Examples of such prime numbers are 2, 3, 5, 7, and 11. Try dividing them with other numbers, excluding 1 and themselves; they won’t divide even. That’s what makes it prime!

Prime numbers are useful in many areas, such as in cryptography to keep your data safe across the internet. Learning how to check for a prime number is one of those first steps toward understanding programming and algorithms.

Simple Program in C# to Check for Prime Numbers

Let’s assume we have a number, and we want to see whether it is a prime or not. We can make this prime number verification program in C#. We will go through it step by step.

 using System;
 class PrimeChecker
 {
 static void Main()
 {
  Console.WriteLine("Enter a number:");
  int number = int.Parse(Console.ReadLine());
  if (IsPrime(number))
  Console.WriteLine(number + " is a prime number.");
  else
  Console.WriteLine(number + " is not a prime number.");
 }
 static bool IsPrime(int number)
 {
 if (number <= 1) return false;
 for (int i = 2; i <= Math.Sqrt(number); i++)
 {
 if (number % i == 0)
 return false;
 }
 return true;
 }
 }

Breaking Down the Code: What Each Part Means

Main() Method

The first point at which the program will start running is here. Inside the main, we are asking the user to input a number and then calling a method named IsPrime to check whether the number is prime or not.

IsPrime Method

The method IsPrime consists of the actual logic, that takes a number and checks if it’s prime or not.

if (number <= 1)

This checks if the number is less than or equal to 1. Since we are interested in numbers greater than 1 only , we immediately return false in this case.

for (int i = 2; i <= Math.Sqrt(number); i++)

Here, we loop from 2 up to the square root of the number. According to the prime number algorithm we loop till the square root.

if (number % i == 0)

This line checks whether the number is divisible by i. If it is then it means the number has a divisor other than 1 and itself-it’s not a prime.

Returning value of either True or False

If we find a divisor then we return false-not prime. When the loop finishes without finding any of the divisors then we return true, which means that the number is prime.

In this simple program, we looked at the logic of checking if a number is prime or not, step by step. Every time you run this program with a different number, it will verify if the number is prime or not.

 

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In this post we will see how to find duplicate characters in a string.For example we can identity how many times character S occurs in a string.

using System;

using System.Collections.Generic;

public class Program
{
public static void Main()
{
string temp="SHUKLAA";
Dictionary<char,bool> chars=new Dictionary<char,bool>();
foreach(char ch in temp)
{
if(!chars.ContainsKey(ch))
chars.Add(ch,true);
else
Console.WriteLine(string.Format("duplicate character is {0}",ch))

}

}
};

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