Cannot implicitly convert void to string in abstract classes

Question

My abstract class code has two errors:

• Cannot implicitly convert "void" to "string" (Line 5, 6, 11, 12, 17, 18, 23, 24)

using static System.Console;

public abstract class DevilHunter
{
    public string Slogan() => Write("Devil May Cry!"); 
    public virtual string Profissao() => Write("Caçar demônio");
}

public class Dante : DevilHunter
{
    public string Estilos() => Write("Possuo 4 estilos de luta");
    public override string Profissao() => Write("Caço dêmonio em grande eSSStilo");
}

public class Nero : DevilHunter
{
    public string DevilBreaker() => Write("Uso Devil Breaker");
    public override string Profissao() => Write("Caço dêmonios ao som de música eletrônica");
}

public class Nico : Nero
{
    public string Dirigir() => Write("Dirige furgão");
    public override string Profissao() => Write("Armeira responsável por criar Devil Breakers para Nero");
}

public class Imprimir
{
    static int Main(string[] args)
    {
        Dante dante = new Dante();
        Nero nero = new Nero();
        Nico nico = new Nico();

        Write(dante.Profissao());
        Write(nero.Profissao());
        Write(nico.Profissao());
        return 0;
    }
}

Answer 1

The structure is wrong for what you are trying to do, if, what you are trying to do is print the class functions in the Console.

You currently have the class structure:

class DevilHunter
{
    public string Slogan() => Write("Devil May Cry!"); 
    public virtual string Profissao() => Write("Caçar demônio");
}

The class DevilHunter has two methods where they must return String, however, the body of both methods call the method Console.Write, and it does not return any value, just write in the Console that text.

If you want the methods to return the texts to use elsewhere (which is ideal), you should use properties in a way that returns the texts properly:

class DevilHunter
{
    public string Slogan => "Devil May Cry!"; 
    public virtual string Profissao => "Caçar demônio";
}

Or if you want them to continue being methods that write on the Console, change from string for void, since nothing comes back:

public void Slogan() => Write("Devil May Cry!"); 

However, the line above will not return anything and cannot be called to assign value to something.

Another mistake within your Main is the call of Write to another Write. You need to specify a valid argument for the method Write, and another Write returns nothing.

Using properties, you can simply pass the property as String and it will work correctly. I also changed the method to WriteLine so that there is a break in line between each profession.

class Program
{
    static int Main(string[] args)
    {
        Dante dante = new Dante();
        Nero nero = new Nero();
        Nico nico = new Nico();

        WriteLine(dante.Profissao); // public virtual string Profissao => "...";
        WriteLine(nero.Profissao);
        WriteLine(nico.Profissao);

        return 0;
    }
}

_{See working on .NET Fiddle.}

The boot method depends on a few things, like the C# version and which compiler you’re using. If you are using a lower version than C# 7.1, this method will not work. You must use the signature static void Main(string[]) and not another, what changes is that you may or may not have arguments.

Signatures allowed to the input method, >= version 7.1, are:

public static void Main() { }
public static int Main() { }
public static void Main(string[] args) { }
public static int Main(string[] args) { }
public static async Task Main() { }
public static async Task<int> Main() { }
public static async Task Main(string[] args) { }
public static async Task<int> Main(string[] args) { }

In the documentation you can better understand about. In language reference also says about these signatures.