C# Professional - Basics & OOP - Exercises

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Previous: ValueTypes - Exercises

Using casting operators

With C#, you can define custom casting implementation between two types. This implementation will be used when casting from one type to the other in your code.

// {
using System;
// }
// User definition
// {
public class User
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public static implicit operator String(User user)
    {
        return $"{user.FirstName} {user.LastName}";
    }
    public static explicit operator User(string text)
    {
        int spaceIndex = text.IndexOf(" ");
        if(spaceIndex >= 1)
        {
            return new User 
            {
                FirstName = text.Substring(0, spaceIndex),
                LastName = text.Substring(spaceIndex + 1)
            };
        }
        return new User { LastName = text };
    }
}
// }
public class Program 
{
    public static void Main(string[] args)
    {
        var user = new User {
            FirstName = "John",
            LastName = "Doe"
        };
        // implict casting
        string userAsString = user;
        Console.WriteLine($"userAsString: {userAsString}");
        // explicit casting
        var otherUser = (User)userAsString;
        Console.WriteLine("User:");
        Console.WriteLine($"  First name: {otherUser.FirstName}");
        Console.WriteLine($"  Last name: {otherUser.LastName}");
    }

Exercise : Implement an implicit and explicit casting

In the following exercise, you have two classes, Car and Vehicle.

The goal is to implement an implicit casting of Car to Vehicle. The casting must respect these guidelines:

The Vehicle.Type property value should be "Car"
The Vehicle.Name property should use the car properties to display all car information with the following format : Brand / Model (Year) / License Plate

Implement implicit casting

// {
using System;
namespace Casting
{
// }
    public class Car
    {
        public string Brand { get; set; }
        public string Model { get; set; }
        public int Year { get; set; }
        public string LicensePlate { get; set; }
        public static implicit operator Vehicle(Car car)
        {
            return null;
        }
        // {
    }
}
// }

Be careful when implementing custom casting operators. They can be useful is certain situations, but using them is not very intuitive and can be misleading.

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Using casting operators

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