I just created my first .NET 6 console app, and instead of the default,
using System;
using System.Collections.Generic;
using System.Linq;
namespace MyApp
{
public class Program
{
public static void Main(string[] args)
{
Console.WriteLine("Hello World!");
}
}
}
I got:
// See https://aka.ms/new-console-template for more information
Console.WriteLine("Hello, World!");
And even when there's no class, the program runs! I took a look at the link provided in the comments, but I don't know if this is a new feature or an old one. If this is a new feature, does that mean C# will be allowing C-style programming hereafter?
It's a new feature of C# 9 or 10. Microsoft documentation says following:
Top-level statements enable you to avoid the extra ceremony required by placing your program's entry point in a static method in a class. The typical starting point for a new console application looks like the following code:
using System;
namespace Application
{
class Program
{
static void Main(string[] args)
{
Console.WriteLine("Hello World!");
}
}
}
The preceding code is the result of running the dotnet new console command and creating a new console application. Those 11 lines contain only one line of executable code. You can simplify that program with the new top-level statements feature. That enables you to remove all but two of the lines in this program:
Console.WriteLine("Hello, World!");
Related
In the Program.cs for .NET 5, you could add methods under the Main(string[] args) method. With .NET 6, the Main method exists, but isn't physically included in the Program.cs file by default. To that end, I'm wondering how you add methods to Program.cs. For example:
// .NET 5
public class Program
{
static void Main(string[] args)
{
// body
}
public static void MyMethodHere()
{
// method body
}
}
How would you add the MyMethodHere() class in .NET 6 in Program.cs without manually typing out the whole Program class and Main method?
You just type out the method that you require and then call it!.
Console.WriteLine("Hello, World from Main!");
MyMethodHere();
static void MyMethodHere()
{
Console.WriteLine("MyMethodHere says hello World!");
}
But you can still type it out in full the same as you done before.
What I have done several times for simple console programs is to create the project with .net 5, this then generates using the "old" template, and then I just update TargetFramework it to .net 6 before I do any coding.
See also the guide from MS: https://learn.microsoft.com/en-gb/dotnet/core/tutorials/top-level-templates
This would work as well:
SayHello();
void SayHello()
{
Console.WriteLine("Hello World");
}
Methods are possible, but without the access modifiers.
The compiler internally creates a static class.
.NET 6 has this new feature that allows minimal main. They unfortunately use it by default in new console projects. Its very confusing. Anyway you can write the old main just like you used to. You just have to type out all the code, or cut and paste from an old project
This question already has an answer here:
How to be dynamically either console application or Windows Application
(1 answer)
Closed 4 years ago.
I have this task given to me and have no idea how to approach it.. Everywhere online says that this isn't possible without .dll or mocking.
The server, when launched with an argument of –w should open a windowed interface that
permits an operator to control the functions of the server. If launched with no arguments it
should operate as previously specified in part 1
(part 1 is a console application)
I don't know if I'm missing something obvious.
Thanks for any help you can give
I don't know where you're seeing on-line that this isn't possible. Every Windows Forms application has a Main method, you just need to modify it a bit.
[STAThread]
static void Main(string[] args)
{
if (args.Length > 0)
{
File.WriteAllText("hello.txt", "foo");
}
else
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(new Form1());
}
}
I added the string[] args argument and then check it. I'm not checking for -w, I'm just checking for any old argument, but you should be able to take it from there.
It's absolutely not impossible. Just add reference to System.Windows.Forms, add it in the using clause, and go from here.
using System;
using System.Collections.Generic;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Linq;
namespace ConsoleWindow
{
class Program
{
static void Main(string[] args)
{
if (args.Contains("-w"))
{
Form1 f1 = new Form1();
f1.ShowDialog();
}
Console.ReadKey();
}
}
}
I'm sure there's some simple answer, but none of the other Stack Overflow posts has helped me. My code will not log to the Console, and it's hard to do anything useful with that state of affairs.
using System;
using System.Diagnostics;
namespace Learning
{
class MainClass
{
public static void Main (string[] args)
{
Debug.Log ("this?");
Debug.Print ("How about this?");
Console.WriteLine ("WORK");
Console.ReadLine ();
}
}
}
I've been able to write to the console before, I don't know why it's being persnickety now.
Probably because your code doesn't actually compile. Log() is a static method of Debugger, not Debug, and it takes three arguments: level, category, and message.
public static void Main (string[] args)
{
System.Diagnostics.Debugger.Log(1, "category", "this?");
System.Diagnostics.Debug.Print ("How about this?");
Console.WriteLine ("WORK");
Console.ReadLine ();
}
It's worth noting that Debug/Debugger methods will not do you any good unless you are Debugging. To start a debugging session in mono, go to the Run -> Debug
You may want to check what kind of application you are using. For example, if you are making a Forms Application, you won't have access to the Console functions.
You can change this by going into the Solution Properties, and changing it from a Windows Forms Application to a Console Application. This won't have any effect on your program, other than it will run a Console alongside.
I know it is possible to code C# .NET apps in Linux using Mono. However, I am wondering about the process interfaces of Linux. Could I use services like getpid(), getppid() and fork() using C# and Mono and running on a Linux environment?
For getpid() and getppid() you could use Syscall in this way:
using System;
using Mono.Unix.Native;
namespace StackOverflow
{
class MainClass
{
public static void Main(string[] args)
{
int pid = Syscall.getpid();
int ppid = Syscall.getppid();
Console.WriteLine ("PID: {0}", pid);
Console.WriteLine ("PPID: {0}", ppid);
}
}
}
You need Mono.Posix.dll
For fork() you can use Process. See example here: creating child process with C#
Documentation about Process Class C#.
It looks cool on MSDN:
Specifies that the method is declared, but its implementation is
provided elsewhere.
So I tried it in a console application:
public class Program
{
[MethodImplAttribute(MethodImplOptions.ForwardRef)]
public static extern void Invoke();
static void Main(string[] args)
{
Invoke();
Console.Read();
}
}
Then what should I do now? Where can I provide the implementation of Program.Invoke?
The usage of ForwardRef goes pretty much like this:
consumer.cs
using System;
using System.Runtime.CompilerServices;
class Foo
{
[MethodImplAttribute(MethodImplOptions.ForwardRef)]
static extern void Frob();
static void Main()
{
Frob();
}
}
provider.cs
using System;
using System.Runtime.CompilerServices;
class Foo
{
// Need to declare extern constructor because C# would inject one and break things.
[MethodImplAttribute(MethodImplOptions.ForwardRef)]
public extern Foo();
[MethodImplAttribute(MethodImplOptions.ForwardRef)]
static extern void Main();
static void Frob()
{
Console.WriteLine("Hello!");
}
}
Now the magic sauce. Open a Visual Studio command prompt and type:
csc /target:module provider.cs
csc /target:module consumer.cs
link provider.netmodule consumer.netmodule /entry:Foo.Main /subsystem:console /ltcg
This uses one of the lesser known functionality of the linker where we're linking managed modules together. The linker is able to gel together same-shaped types (they need to have the exact same methods, etc.). ForwardRef is the thing that actually lets you provide implementation elsewhere.
This example is kind of pointless, but you can imagine things getting more interesting if a single method is implemented in a different language (e.g. IL).
My understanding is that ForwardRef acts in the same way as extern, and is intended for guiding the runtime when the language you are using lacks direct support (via extern in C#). As such, the usage should be very similar to the extern modifier, most notably using [DllImport(...)].