With .NET Interactive: a .NET based jupyter kernel you can run small snippets of C# (and F#) code in cells and take advantage of a repl like workflow to explore the language.
1 Why notebooks?
My first introduction to coding was in Python via Jupyter Notebooks - this interactive environment with immediate feedback from running each cell was invaluable in my learning, and I still regularly open up an ipython in a terminal when I quickly want to test some behaviour e.g. how do I add things to the start of a list in python again?
Of course doing all your coding in notebooks will leave some pretty big knowledge gaps with things like packaging, project structure, testing and other practices around development (although it can be done in notebooks!), but I still think it’s useful to help build understanding around the fundamentals of the language and its ecosystem.
2 Getting started
You need to install the .NET6 SDK, VSCode and thePolyglot Notebooks extension.
Then create a .ipynb file, pick .NET Interactive as your kernel and start coding:
You can also read more about how microsoft made this possible in their devblog.
3 C# 101 Challenges
Here’s a collection of challenges solved in notebooks. These were taken from the C# 101 course to build some muscle memory and get some hands on practice with C# syntax
3.1 Combining branches and loops
See if you can write C# code to find the sum of all integers 1 through 20 that are divisible by 3.
int sum = 0;
for (int i=1; i <=20; i++){
if (i % 3 == 0){
sum += i;
}
}
Console.WriteLine(sum);633.2 Working with lists
Make a list of groceries you need called
groceries. Can you print out “buy <grocery>!” for every item? What’s the 3rd item of the list? Is that the same asgroceries[3]?Make sure to add “toothpaste”. Remove your least favorite item. Now what’s third on the list?
var groceries = new List<string> {"cheese", "bread", "biscuits", "coffee"};
groceries.Add("toothpaste");
groceries.Remove("biscuits");
foreach (string grocery in groceries){
Console.WriteLine($"buy {grocery}");
}buy cheese
buy bread
buy coffee
buy toothpasteMake a list of groceries, then sort them! what is the index that ‘Carrots’ is at? Try making a list of numbers! Do they sort in the way you expect? Print out the lists that you’ve made.
var groceries = new List<string> {"cheese", "biscuits", "coffee", "carrots"};
int carrotIndex = groceries.IndexOf("carrots");
Console.WriteLine($"carrots at {carrotIndex} before sorting.");
groceries.Sort();
carrotIndex = groceries.IndexOf("carrots");
Console.WriteLine($"carrots at {carrotIndex} after sorting.");carrots at 3 before sorting.
carrots at 1 after sorting.3.3 Fibonacci to 20th number
Make and print a list that has the first 20 fibonacci numbers.
// can use recursion too, but we're practicing lists here
var fibonacciNumbers = new List <int> {1,1};
int idx = 1;
while (fibonacciNumbers.Count <20){
int currNum = fibonacciNumbers[idx];
int prevNum = fibonacciNumbers[idx-1];
int nextNum = currNum + prevNum;
fibonacciNumbers.Add(nextNum);
idx ++;
}
foreach(int num in fibonacciNumbers){
Console.WriteLine(num);
};1
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41813.4 Classes
It has a 10-digit number that uniquely identifies the bank account. It has a string that stores the name or names of the owners. The balance can be retrieved. It accepts deposits. It accepts withdrawals. The initial balance must be positive. Withdrawals cannot result in a negative balance. Create a way to list out the list of transactions, including the time and notes.
using System.Collections.Generic;
public class Transaction
{
// Properties
public decimal Amount { get; }
public DateTime Date { get; }
public string Notes
{
get;
}
// Constructor
public Transaction(decimal amount, DateTime date, string note)
{
this.Amount = amount;
this.Date = date;
this.Notes = note;
}
}
public class BankAccount
{
public string Number { get; }
public string Owner { get; set; }
public decimal Balance
{
get
{
decimal balance = 0;
foreach (var item in allTransactions)
{
balance += item.Amount;
}
return balance;
}
}
private static int accountNumberSeed = 1234567890;
private List<Transaction> allTransactions = new List<Transaction>();
public BankAccount(string name, decimal initialBalance)
{
this.Owner = name;
this.Number = accountNumberSeed.ToString();
accountNumberSeed++;
MakeDeposit(initialBalance, DateTime.Now, "Initial balance");
}
public void MakeDeposit(decimal amount, DateTime date, string note)
{
if (amount <= 0)
{
throw new ArgumentOutOfRangeException(nameof(amount), "Amount of deposit must be positive");
}
var deposit = new Transaction(amount, date, note);
allTransactions.Add(deposit);
}
public void MakeWithdrawal(decimal amount, DateTime date, string note)
{
if (amount <= 0)
{
throw new ArgumentOutOfRangeException(nameof(amount), "Amount of withdrawal must be positive");
}
if (Balance - amount < 0)
{
throw new InvalidOperationException("Not sufficient funds for this withdrawal");
}
var withdrawal = new Transaction(-amount, date, note);
allTransactions.Add(withdrawal);
}
public void ListTransactions()
{
//write header
Console.WriteLine($"Date\t\t\tAmount\t\tNotes");
foreach (var transaction in allTransactions)
{
Console.WriteLine($"{transaction.Date}\t{transaction.Amount}\t\t{transaction.Notes}");
}
}
}Thanks to the interactive environment, we can use this class and play about with it:
var account = new BankAccount("Ismail", 1000);
Console.WriteLine($"Account {account.Number} was created for {account.Owner} with {account.Balance} dollars");
account.MakeWithdrawal(500, DateTime.Now, "Rent payment");
Console.WriteLine(account.Balance);
account.MakeDeposit(100, DateTime.Now, "Friend paid me back");
Console.WriteLine(account.Balance);Account 1234567890 was created for Ismail with 1000 dollars
500
600account.ListTransactions();Date Amount Notes
22/01/2023 23:36:54 1000 Initial balance
22/01/2023 23:36:54 -500 Rent payment
22/01/2023 23:36:54 100 Friend paid me back