Cursusinhoud

C# Beyond Basics

1. Additional Structures & File Handling

What are Lists?Practicing List Declaration List Methods What are Dictionaries?Practicing Dictionaries Reading Files using StreamReader Reading Files using File Methods Writing Files Error Handling Practicing Error Handling

2. Structs & Enumerators

What are Structs?Defining & Using a Structure Practicing Structs Structs with Other Data Structures Struct Methods Correctly Accessing Fields in Struct Methods Practicing Methods Struct Constructors Practicing Constructors Enumerators Practicing Enumerator

3. Introduction to Object-Oriented Programming (OOP)

What is Object-Oriented Programming?Defining Classes Practice: Creating Classes Class Objects Class Objects vs Struct Objects Practice: Objects Class Methods Practice: Methods Class Constructors Practice: Constructors

4. OOP Essentials

Derived Classes Derived Classes Practice Common Access Modifiers Access Modifiers Practice The `static` Keyword Practicing `static` Keyword Method Overloading Method Overloading Practice

5. OOP Principles

What are the Principles of OOP?Inheritance Practicing Inheritance Polymorphism Practicing Polymorphism Encapsulation Encapsulation Practice Abstraction Abstraction Practice What's Next?

Practicing Error Handling

The try-catch syntax has an additional syntax which allows us to catch specific types of errors and deal with them separately:

index.cs


              1234567891011121314151617
            
try 
{
    // code
}
catch (ExceptionType errorVarName)
{
    // code
}
catch (ExceptionType errorVarName)
{
    // code
}
...
finally
{
    // code
}

The type Exception we used in the previous chapter simply catches all kinds of errors however there are some subtypes of Exception which catch more specific kinds of errors. Following are some common exception types:

DivideByZeroException: There's a division by zero;
FileNotFoundException: The file we're accessing doesn't exist;
KeyNotFoundException: The dictionary key doesn't exist;
IndexOutOfRangeException: The specified index of an array or list is invalid.

The term errorVarName is a variable which stores the Exception object, and has information like the error message which can be accessed through errorVarName.Message. We can omit that in case we're not using it:

index.cs


              12345678910111213
            
try 
{
    // code
}
catch (ExceptionType)
{
    // code
}
...
finally
{
    // code
}

Here's an example of using this kind of try-catch block:

index.cs


              123456789101112131415161718192021222324252627
            
using System;

class Program
{
    static void Main(string[] args)
    {
        int[] myArray = { 0, 2, 4, 6, 8, 10 };
        int i = 0;
        
        while (true)
        {
            try
            {
                Console.Write(myArray[i] / i + " ");
                i++;
            }
            catch(DivideByZeroException)
            {
                i++;
            }
            catch(IndexOutOfRangeException)
            {
                break;
            }
        }
    }
}

Now using these concepts. Fill in the blanks with relevant exception types in the following code to complete the challenge.

index.cs


              1234567891011121314151617181920212223242526272829303132333435
            
using System;
using System.Collections.Generic;

class Program
{
    static void Main(string[] args)
    {
        int[] numbers = { 1, 2, 5, 7, 9 };
        var numberNames = new Dictionary<int, string>();

        numberNames.Add(1, "One");
        numberNames.Add(2, "Two");
        numberNames.Add(5, "Five");
        numberNames.Add(9, "Nine");

        int i = 0;
        while (true)
        {
            try
            {
                int key = numbers[i];
                Console.WriteLine($"{key} is {numberNames[key]}");
                i++;
            }
            catch (___)
            {
                break;
            }
            catch (___)
            {
                numberNames.Add(7, "Seven");
            }
        }
    }
}

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Sectie 1. Hoofdstuk 10

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Cursusinhoud

C# Beyond Basics

1. Additional Structures & File Handling

2. Structs & Enumerators

3. Introduction to Object-Oriented Programming (OOP)

4. OOP Essentials

Derived Classes Derived Classes Practice Common Access Modifiers Access Modifiers Practice The `static` Keyword Practicing `static` Keyword Method Overloading Method Overloading Practice

5. OOP Principles

What are the Principles of OOP?Inheritance Practicing Inheritance Polymorphism Practicing Polymorphism Encapsulation Encapsulation Practice Abstraction Abstraction Practice What's Next?

Practicing Error Handling

The try-catch syntax has an additional syntax which allows us to catch specific types of errors and deal with them separately:

index.cs


              1234567891011121314151617
            
try 
{
    // code
}
catch (ExceptionType errorVarName)
{
    // code
}
catch (ExceptionType errorVarName)
{
    // code
}
...
finally
{
    // code
}

DivideByZeroException: There's a division by zero;
FileNotFoundException: The file we're accessing doesn't exist;
KeyNotFoundException: The dictionary key doesn't exist;
IndexOutOfRangeException: The specified index of an array or list is invalid.

index.cs


              12345678910111213
            
try 
{
    // code
}
catch (ExceptionType)
{
    // code
}
...
finally
{
    // code
}

Here's an example of using this kind of try-catch block:

index.cs


              123456789101112131415161718192021222324252627
            
using System;

class Program
{
    static void Main(string[] args)
    {
        int[] myArray = { 0, 2, 4, 6, 8, 10 };
        int i = 0;
        
        while (true)
        {
            try
            {
                Console.Write(myArray[i] / i + " ");
                i++;
            }
            catch(DivideByZeroException)
            {
                i++;
            }
            catch(IndexOutOfRangeException)
            {
                break;
            }
        }
    }
}

Now using these concepts. Fill in the blanks with relevant exception types in the following code to complete the challenge.

index.cs


              1234567891011121314151617181920212223242526272829303132333435
            
using System;
using System.Collections.Generic;

class Program
{
    static void Main(string[] args)
    {
        int[] numbers = { 1, 2, 5, 7, 9 };
        var numberNames = new Dictionary<int, string>();

        numberNames.Add(1, "One");
        numberNames.Add(2, "Two");
        numberNames.Add(5, "Five");
        numberNames.Add(9, "Nine");

        int i = 0;
        while (true)
        {
            try
            {
                int key = numbers[i];
                Console.WriteLine($"{key} is {numberNames[key]}");
                i++;
            }
            catch (___)
            {
                break;
            }
            catch (___)
            {
                numberNames.Add(7, "Seven");
            }
        }
    }
}

Was alles duidelijk?

Bedankt voor je feedback!

Sectie 1. Hoofdstuk 10