List of Posts written during Oct 2022

This is a list of of posts written during the month Oct 2022
(Rev. 03-Dec-2022)

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List of Posts

This is the complete list of categories of posts written during Oct 2022. They have been ordered by the publish date, with the most recent first.

  1. Published: 03-Oct-2022
    An interface is a collection of related functionality. An audio player is an audio player only if it implements the ability to play, pause, stop, etc., We can say that the functions play, pause, stop are together an interface called IAudioControls. An interface is a set of functions grouped together under the interface keyword. An interface cannot contain instance data members - they can, however, contain static data members - but that's an entirely different thing because static members are tied to a class or interface, not to a specific object. In this tutorial we examine various aspects of interfaces from C# perspective.


  2. Published: 04-Oct-2022
    In this tutorial we take a hypothetical problem to build towards the concept of generics. First we explore a few bad solutions. Then we explain a perfect solution by generics. That leads us to list the benefits of using generics. We conclude with the constraints on generic parameters.


  3. Published: 07-Oct-2022
    We expect you have a very general understanding of object oriented programming blocks like classes and structs. In this tutorial we have a quick look at a class in C#. Then we have a discussion of the structs, and then a detailed look on the record keyword. The tutorial closes with "When to use a record".


  4. Published: 10-Oct-2022
    Write a C# class called CData to hold a float type of quantity. This class also contains an enumeration of two members - Meter and Centimeter - to specify the unit of the quantity stored. Add a constructor and a public function called Convert. The Convert function converts the data to meter if the data held is in centimeters, and to centimeters if the data held is in meters. The Convert function displays the result correct to 2 decimal places. Test the function by creating an object in the main function.


  5. Published: 10-Oct-2022
    This exercise is an exercise just for the sake of practice in static and consts in a class. Create a class called CBankAccount that contains a static member to hold the name of the bank, a constant member to store the minimum balance (100) that a customer has to maintain, another constant member for rate of interest (5) and a yet another constant member for periodicity (4 months) of applying interest. Also add an instance member to hold the balance of a customer in dollars. Add a static constructor to initialize the name of the bank by obtaining input from the user. Add a static function called RenameBank that can be used to give a new name to the bank. Add two functions called Withdraw(int amount) and Deposit(int amount) that update the balance after a successful transaction and print it. Also add a function AddInterest() that calculates simple interest for four months and updates the balance. Test the class in Main.


  6. Published: 11-Oct-2022
    Create a class MyClock that contains only one public function "void Tick(Object?)". This signature matches the signature of the TimerCallback delegate defined in the System.Threading.Timer class of dotnet. The "void Tick" function prints the current system time on the console (use DateTime.Now). Inside Main create a System.Threading.Timer by using a suitable constructor that calls "void Tick" once every second. Run the program to verify that you have a clock that prints the current system time. You will have to study the documentation of System.Threading.Timer class.


  7. Published: 14-Oct-2022
    Create a class called MyNumber with a property called Number of Int32 type. This class should contain an event delegate that takes one argument of Int32 type. The class MyNumber should raise this event when the Number property changes. The changed value should be sent as an argument to all delegates that register to this event. Inside Main create an object of MyNumber and attach an event handler that prints the changed value. The event handler should be an anonymous expression lambda that receives an Int32 argument and prints the number to console. Test the project by changing the Number property. If you did the things correctly, then you should see the event handler called. This might be a difficult one. So please go through the solution if you find the question itself difficult to understand.


  8. Published: 16-Oct-2022
    We have to store four properties of a record - student id of string type and marks in three subjects of Int32 type. Inside main create an array of 10 items. Use a for-loop to fill the array. Each item can be filled with random data. Then, use a select query on the array to project two fields only - Student ID and marks in the first subject. Print the queried data with a suitable loop. Use var keyword as far as possible.


  9. Published: 17-Oct-2022
    This tutorial introduces you to the IEnumerable interface and its practical significance. After that we discuss the internal workings of this interface. We demonstrate how the yield keyword can be used to return an IEnumerable from a function. The tutorial concludes with a C# program to efficiently print a fibonacci series by using the yield keyword and statement.


  10. Published: 19-Oct-2022
    In this tutorial we learn the use of Select, Where, OrderBy and OrderByDescending functions provided by C# LINQ. A program has been used to explain these functions. This will help you get started but experience is the best teacher. So all I can help you is get started.


  11. Published: 19-Oct-2022
    In this tutorial we learn about FirstOrDefault, Single, First and SingleOrDefault extension methods available on an IEnumerable. Use FirstOrDefault for finding the first element that matches a condition. It returns the default value if no matching records exist. "First" does the same thing but throws an exception instead. SingleOrDefault returns the default value if exactly one record cannot be found. There is one more called Find which should be used if the search has to be by a primary key value.


  12. Published: 21-Oct-2022
    C# Linq provides a GroupBy extension method for grouping records on a common key. This tutorial starts with a brief introduction to the concept of grouping. Then we use the GroupBy extension to group various records on a property called last name so that customers of the same last name are grouped together. The result is then displayed on console.


  13. Published: 22-Oct-2022
    Two lists can be joined on common key or keys by using the Join extension method. The concept of a join in linq is exactly the same as in SQL of databases. A detailed concept of joins is far too complex to be described in a single tutorial. So this tutorial has been kept simple to help you get started and walk you to a point where a further study is easier.


  14. Published: 24-Oct-2022
    Database connectivity is required in almost every project. It is best done with the help of EF Core libraries. The good thing is that the steps for database connectivity are fairly standardized now. The same steps are used for C# console applications, the same are for a C# winforms, C# WPF and even C# web applications. This tutorial walks you through the steps required for creating a database. In the next tutorials we shall explain the create, read, update and delete operations.


  15. Published: 25-Oct-2022
    Create a list of Category records with ID and Name as properties. Add 3 items to this list - (ID:1, Name:"For Men"), (2, "For Women") and (3, "For Kids"). Then create a list of SubCategory records with ID, Name and CategoryFK as properties. The property CategoryFK is a foreign key for the ID property of a Category. Add these items - (ID:1, CategoryFK:1, Name:"Shirts"), (2, 1, "T Shirts"), (3, 1, "Trousers"), (4, 2, "Skirts"), (5, 2, "Shoes"). Use the GroupJoin extension to present dresses of men under a heading "For Men", dresses of women under "For Women" and likewise for kids.


  16. Published: 26-Oct-2022
    This tutorial continues from the previous tutorial where we created a database and a table in it. We shall now add a blog record to the table and save it. Then we shall extract it back and make a change to the Heading property, and save it again. Then we shall extract it back and delete it from the table. Finally, we shall display the count of records in the table, and verify that it is shown zero.


  17. Published: 27-Oct-2022
    Discards are denoted by an underscore. They can be thought of identifiers that receive an assignment, but the assignment is discarded and not available for use. A discard is most commonly used to indicate that the return type of a function has been ignored intentionally. But there are other less known use-cases of a discard. This tutorial demonstrates them by using various program examples - using a discard to (1) ignore a function return, (2) ignore the return of a tuple, (3) ignore an out parameter of a function, (4) default case of a switch expression and (5) as a forced assignment.


  18. Published: 28-Oct-2022
    Pattern matching is used to test an expression. In this tutorial we take various snippets to learn expression matching. One of the uses is to test if a variable matches a data type. Pattern matching is also used in switch expressions to match the arms against constants, strings or logical conditions. Pattern matching is also used for comparison of multiple inputs passed as expressions of tuple types. Lists can also be matched if you are using C# 11 or later.


  19. Published: 30-Oct-2022
    In this tutorial we take common topics on strings, such as creating strings, on concatenation of strings, extraction of a substring, and truncation, null testing, searching a string within another, and comparison of two strings.


  20. Published: 30-Oct-2022
    Suppose there is a string s = "aubcd123paqeaw". Write three programs (1) Write a program to count the number of 'a' in this string. (2) Write a program to extract the numeric part into a string variable and display it. (3) Replace all vowels by underscore.