I have tried to compile code from Deitel's C# 2010 for programmers. I copied it exactly out of the book, but it still can't find main, even though I declared it in one of the classes. Here is a look at the two classes:
For GradeBookTest:
// Fig. 4.2: GradeBookTest.cs
// Create a GradeBook object and call its DisplayMessage method.
public class GradeBookTest
{
// Main method begins program execution
public static void Main(string[] args)
{
// create a GradeBook object and assign it to myGradeBook
GradeBook myGradeBook = new GradeBook();
// call myGradeBook's DisplayMessage method
myGradeBook.DisplayMessage();
} // end Main
} // end class GradeBookTest
Now for the GradeBook class:
// Fig. 4.1: GradeBook.cs
// Class declaration with one method.
using System;
public class GradeBook
{
// display a welcome message to the GradeBook user
public void DisplayMessage()
{
Console.WriteLine( "Welcome to the Grade Book!" );
} // end method DisplayMessage
} // end class GradeBook
That is how I copied them. Here is how they appeared in the book:
1 // Fig. 4.2: GradeBookTest.cs
2 // Create a GradeBook object and call its DisplayMessage method.
3 public class GradeBookTest
4 {
5 // Main method begins program execution
6 public static void Main( string[] args )
7 {
8 // create a GradeBook object and assign it to myGradeBook
9 GradeBook myGradeBook = new GradeBook();
10
11 // call myGradeBook's DisplayMessage method
12 myGradeBook.DisplayMessage();
13 } // end Main
14 } // end class GradeBookTest
and
// Fig. 4.1: GradeBook.cs
// Class declaration with one method.
using System;
public class GradeBook
{
// display a welcome message to the GradeBook user
public void DisplayMessage()
{
Console.WriteLine( "Welcome to the Grade Book!" );
} // end method DisplayMessage
} // end class GradeBook
I don't see why they are not working. Right now I am using Visual Studio Pro 2010. Any Thoughts?
You probably created the wrong type of project at Visual Studio. To be able tu run a project, it must be an application. This means it could be a web application, web site, windows application, console application and so on.
The easier for you to begin is with the console application. Open Visual Studio and point to File > New > Project > Visual C# > Windows > Console Application.
When you create it, you'll notice a Program.cs file. There you can find the main point of your application.
Tip: you might want to add another line below the call of DisplayMessage, which is
Console.ReadLine();
Otherwise the prompt will close so fast that you won't be able to read it.
Good luck on your study!
Related
When making the file, I am thinking of selecting a console application. But which target framework do I choose? Is this incorrect? Also, I am having trouble figuring out how to make a method in the class Program that is able to be called in the Main method. Can someone give me some advice?
one thing you can do is using interface to keep your code clean; for example :
you create an interface like this:
public interface IQuestionSolving
{
public void Solution();
}
you create some question class :
public class Question1 : IQuestionSolving
{
public void Solution()
{
}
}
and you use it like this :
static void Main(string[] args)
{
IQuestionSolving solve = new Question1();
solve.Solution();
Console.ReadKey();
}
now each time you solve a question you need to change
IQuestionSolving solve = new Question1();
to
IQuestionSolving solve = new Question2(); // 2 3 4 .. etc
you can extract your project as template so you dont have to do this each time .
or you can just use one solution and many classes .
This will get you started with Visual Studio:
Create a new console project - use the latest version of C#, which is probably what VS will "suggest" to you. Currently that's .NET 6 or .NET 7
A modern (net 6 or later) console app lets you start writing code immediately. You could create a method and then call the method right in this little Program.cs file that you start out with. However, I would probably do the following instead:
a) Create a new class for your "problem"
b) In that class create a method that solves the problem.
c) In your Program.cs add a using statement to use the namespace that your new class uses
d) In your program.cs instantiate that class and call its method/test its method
Here is an example:
Program.cs
using LeetCodeProject;
var solver = new Problem001_CalculateSquareRoot();
var solution = solver.calculate_square_root(8);
Console.WriteLine(solution);
Console.WriteLine("Press any key...");
Console.ReadKey();
Problem001_CalculateSquareRoot.cs (solves one leetcode problem)
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace LeetCodeProject
{
public class Problem001_CalculateSquareRoot
{
public double calculate_square_root(int number)
{
double root = 1;
int i = 0;
while (true)
{
i = i + 1;
root = (number / root + root) / 2;
if (i == number + 1)
{
break;
}
}
return root;
}
}
}
Now you can just add new classes for each problem, and as you work on them just edit Program.cs to create the class you are currently working with and calls its solution methods.
I can (and would - and actually have, in similar cases) implement an interface for this, but the goal here is not to get into OO design principles, but just to get you started so you can get to work on the leetcode problems...once you have a few done you can start thinking about better organization of the code.
This question already has answers here:
Could not find 'WindowsFormsApplication1.Program' specified for Main method after renaming name space
(3 answers)
Closed 2 years ago.
I have this problem where i have 2 files inside a project. One called Program.cs and another called Book.cs
I tried running the Program.cs but it comes up with the error: "Could not find 'Program' specified for Main method".
Here's the code for Program.cs
using System;
namespace Classes_Objects
{
class Program
{
public static void Main(string[] args)
{
Book book1 = new Book();
book1.title = "Harry Potter";
book1.author = "JK Rowling";
book1.pages = 400;
Console.WriteLine(book1.pages);
Console.ReadLine();
}
}
}
Here's the code for Book.cs
using System.Text;
using System.Threading.Tasks;
namespace Classes_Objects
{
class Book
{
public string title;
public string author;
public int pages;
}
}
Please download .net core SDk after that open VS code, open the folder where you want to execute .cs programs and install C# plugin
after that please try these commands which worked for me
open terminal in VS code and type dotnet new console
it will create Program.cs file , .csproj, obj folder
Create your file Book.cs and implement both of your book code and program code in that folder which should have same namespace name
then run this command dotnet run .\Program.cs
The Output will be :
400
Remember in your code there is Console.ReadLine(); after printing the value.
I have these requirements coming from client every week for some new logic or verification. For which I have to code new logic (basically some if-else and loops) and launch a new build for him. I want to avoid it by simply coding my logic in visual studio then writing a utility to export it to XML or something and send it to client via e-mail. He just have to place this file in some appropriate folder and the application will behave considering this logic.
Please suggest some solutions. My platform is C# Asp.Net.
Thanks
Using .NET 4.6 and the NuGetPackage Microsoft.CodeAnalysis.Scripting you could implement a scripting engine to run your c# code residing in a textfile without building an assembly.
Install NuGet Package:
Install-Package Microsoft.CodeAnalysis.Scripting.CSharp
Implement TestClass with some basic C#-Code-Content:
class Program
{
static void Main(string[] args)
{
TestScript();
}
private static async void TestScript()
{
// Code snippet: a class with one string-property.
string codeContent = #" using System;
public class ScriptedClass
{
public string HelloWorld { get; set; }
public ScriptedClass()
{
HelloWorld = ""Hello Roslyn!"";
}
}
new ScriptedClass().HelloWorld";
// Instanciate CSharpScriptEngine
var engine = new CSharpScriptEngine();
// Execute code and return string property (HelloWorld)
var scriptingState = await engine.ExecuteAsync(codeContent);
// Print return value from CSharpScript
Console.WriteLine("Returned from CSharpScript: {0}", scriptingState.ReturnValue);
Console.WriteLine("Press any key to continue.");
Console.ReadKey();
}
}
Implement a ScriptingEngine:
internal sealed class CSharpScriptEngine
{
public async Task<ScriptState<object>> ExecuteAsync(string codeContent)
{
// Add references from calling assembly
ScriptOptions options = ScriptOptions.Default.AddReferences(Assembly.GetExecutingAssembly());
// Run codeContent with given options
return await CSharpScript.RunAsync(codeContent, options);
}
}
Read ScriptCode from textfile:
So basically you could read some csharpcode from a textfile of your choice and run them on the fly:
private static async void TestScript()
{
// Read in script file
string codeContent = File.ReadAllText(#"C:\Temp\CSharpScriptTest.cs");
var engine = new CSharpScriptEngine();
// Run script
var scriptingState = await engine.ExecuteAsync(codeContent);
Console.WriteLine("Returned from CSharpScript: {0}", scriptingState.ReturnValue);
Console.WriteLine("Press any key to continue.");
Console.ReadKey();
}
In case you are wondering how all of this works under the hood, Roslyn will create a so called submission from your script code. A submission is an in memory assembly containing the types generated around your script code, which can be identified among the assemblies in the current AppDomain by a ℛ prefix in the name.
The precise implementation details are not important here (though, for example, scriptcs heavily relies on understanding in detail how Roslyn works to provide its extra features), but it's important to know that submissions can be chained together. When they are chained, variables, methods or classes defined in an earlier submission are available to use in subsequent submissions, creating a feature of a C# REPL (read-evaluate-print loop).
C# and Visual Basic - Use Roslyn to Write a Live Code Analyzer for Your API
Hope it helps
I have the following code which works fine when I use it within a Windows Forms application, however the application I'm writing needs to run as a Windows service, and when I moved my code into the Windows Service template in Visual Studio 2015 Community Edition, I get the following error.
Cannot implicitly convert type "MyWindowsService.Main" to "System.ComponentModel.ISynchronizeVoke". An explicit conversion exists (are you missing a cast?)
Could anyone shed some light on why I am getting this error, and what I need to do to resolve it?
The code which throws the error is the line below, and it is located within the OnStart method of my main class (named Main.cs). The code is used to create an instance of the DataSubscriber class (AdvancedHMI library).
dataSubscribers[dataSubscriberIndex].SynchronizingObject = this;
It has to have something to do with the fact that the code is in a Windows service template, because using this works perfectly in my forms application running the same code.
UPDATE
Correction, I've attempted to cast this to the required type, and now get the following error on run.
Additional information: Unable to cast object of type 'MyWindowsService.Main' to type 'System.ComponentModel.ISynchronizeInvoke'.
Code:
dataSubscribers[dataSubscriberIndex].SynchronizingObject = (System.ComponentModel.ISynchronizeInvoke)this;
UPDATE
I've included the entire contents of the Main.cs file from my Windows Service application.
using System.Data;
using System.Diagnostics;
using System.Linq;
using System.ServiceProcess;
using System.Text;
using System.Threading.Tasks;
using MySql.Data.MySqlClient;
using AdvancedHMIDrivers;
using AdvancedHMIControls;
using MfgControl.AdvancedHMI.Drivers;
using MfgControl.AdvancedHMI.Controls;
using System.Collections.ObjectModel;
namespace PLCHistoricDataHarvester {
public partial class Main : ServiceBase {
private EthernetIPforCLXCom commObject = new EthernetIPforCLXCom();
private globals globals = new globals();
private Dictionary<String, String> operationLines = new Dictionary<String, String>();
private Dictionary<String, String> tags = new Dictionary<String, String>();
private Collection<DataSubscriber> dataSubscribers = new Collection<DataSubscriber>();
private int harvesterQueueCount = 0;
private string harvesterInsertValues = String.Empty;
public Main() {
InitializeComponent();
}
protected override void OnStart(string[] args) {
// Initialize our harvester program
initializeHarvester();
Console.WriteLine("The program has started");
}
protected override void OnStop() {
// Call code when the service is stopped
Console.WriteLine("Program has stopped");
Console.ReadLine();
}
public void initializeHarvester() {
// First, we connect to the database using our global connection object
globals.dbConn.DatabaseName = "operations";
if (!globals.dbConn.IsConnect()) {
// TODO: Unable to connect to database. What do we do?
}
// Second, we connect to the database and pull data from the settings table
globals.initializeSettingsMain();
// Set IP address of PLC
commObject.IPAddress = globals.getSettingsMain("Processor_IP");
// Pull distinct count of our parent tags (Machines ex: Line 1, etc)
operationLines = globals.getOperationLines();
// If we have at least 1 operation line defined...we continue
if (operationLines.Keys.Count > 0) {
//Now we loop over the operation lines, and pull back the data points
int dataSubscriberIndex = 0;
foreach (KeyValuePair<String, String> lines in operationLines) {
int line_id = int.Parse(lines.Key);
string name = lines.Value;
tags = globals.getTags(line_id);
// If we have at least 1 tag for this operation line, we continue...
if (tags.Keys.Count > 0 && tags["tags"].ToString().IndexOf(",") != -1) {
// Create our dataSubscriber object
dataSubscribers.Add(new DataSubscriber());
dataSubscribers[dataSubscriberIndex].SynchronizingObject = (ISynchronizeInvoke)this;
dataSubscribers[dataSubscriberIndex].CommComponent = commObject;
dataSubscribers[dataSubscriberIndex].PollRate = 1000;
dataSubscribers[dataSubscriberIndex].PLCAddressValue = tags["tags"];
dataSubscribers[dataSubscriberIndex].DataChanged += new EventHandler<MfgControl.AdvancedHMI.Drivers.Common.PlcComEventArgs>(subscribeCallback);
// Increment our dataSubscriberIndex
dataSubscriberIndex++;
}
}
}
}
private void subscribeCallback(object sender, MfgControl.AdvancedHMI.Drivers.Common.PlcComEventArgs e) {
// code removed as it is irrelevant
}
}
}
The error message says this:
An explicit conversion exists (are you missing a cast?)
So add a cast like this:
dataSubscribers[dataSubscriberIndex].SynchronizingObject = (ISynchronizeInvoke)this;
^^^^^^^^^^^^^^^^^^^^
//Add this
If you've got a console app, the easiest way to convert it to a windows service is by using Topshelf, a nuget package which lets you run in either console mode or nt service mode.
Here's the quickstart guide.
We use it to write services all the time and it helps you avoid this kind of fragile shenanigans.
after along time of searching via google, I decided to poste my problem here.
First: I am total C# Noob. I am using a Macro Recorder from Jitbit and I have no choice to use a different. The Problem is in the Macro Recorder, it is missing some essential things.
Like reading a text file into a variable and paste this variable via Clipboard :-(
However the good thing is, the tool support "some" type of native C# Code
If I open the C# Command I get this:
public class Program
{
public static void Main()
{
System.Windows.Forms.MessageBox.Show("test");
}
}
And the C# program has to follow also these rules:
=> This Code MUST contain a class named "Program" with a static method "Main"
I already used google and found code that should do the job but I get errors, I guess the
code doesn`t follow the above rules.
This is what I found and tried:
using System;
using System.IO;
public class Program
{
public static void Main()
{
// Read the file as one string.
System.IO.StreamReader myFile =
new System.IO.StreamReader("Counter.txt");
string counter = myFile.ReadToEnd();
myFile.Close();
// Load string into clipboard
Clipboard.SetDataObject( counter, true );
}
}
I always get the error : "Line 15: The Name Clipboard is not existing in the context"?!?
I hope that someone can explain a noob (me) what is wrong and what is the correct code.
Thanks.
add reference to System.Windows.Forms
using System;
using System.IO;
using System.Windows.Forms;
public class Program
{
[STAThread]
public static void Main()
{
Clipboard.SetDataObject(File.ReadAllText("Counter.txt"), true);
}
}
Note that to Avoid the ThreadStateException you need to applying the STAThread attribute to your Main() function