CODEWITHSUNDEEP
c#
JebKerman
JebKerman

Reputation: 23

How do I specify entry points or find errors in my code to stop "Program has more than one entry point." in C#?

error image I have just started learning C# a few weeks ago and do have a year and half of experience in Python, so it would be better if i could get a more detailed explanation on why am i getting this error. I have tried searching on google to see if anyone has gotten this error before, but i am not able to understand the solutions and how to put in the solution. Here's the code, find anything wrong?

using System;

namespace RectangleApplication
{
    class Rectangle
    {
        double length;
        double width;

        public void Acceptdetails()
        {
            length = 4.5;
            width = 3.5;
        }

        public double GetArea()
        {
            return length * width;
        }

        public void Display()
        {
            Console.WriteLine("length: {0}", length);
            Console.WriteLine("Width: {0}", width);
            Console.WriteLine("Area: {0}", GetArea());
        }
    }

    class ExecuteRectangle
    {
        static void Main(string[] args)
        {
            Rectangle r = new Rectangle();
            r.Acceptdetails();
            r.Display();
            Console.ReadLine();
        }
    }
}

Upvotes: 0

Views: 252

Answers (2)

TJR
TJR

Reputation: 3732

In the error it says line: 9 File: Program.cs

Your code is in EmptyCSharpFile.cs

There is another .cs file called Program.cs that is in your project that has a Main method, and that is what is causing the problem. Double clicking on an error should take you to the line of code that is failing.

Upvotes: 3

jalex
jalex

Reputation: 1524

The posted code is correct.

If you read about the Main() method, you see that it has the following requirements to be an entry point

  • Must be static method inside a class

  • Must be called Main()

  • Can have public, internal, protected or private access modifiers

  • Can have arguments capturing the command line arguments

     static void Main(string[] args)
 {
 }

  • Can have zero arguments

     static void Main()
 {
 }

  • Must have only one such method defined within each project.

    In your case there might be another file, called Program.cs that also defines a Main() method. Delete this other file, or move the main method from class ExecuteRectangle to class Program.

  • For winforms applications the main methods loads the main form and displays it using Application.Run().

On a related note, since you are learning about C# and OOP, consider the code below with similar functionality as yours, but with standard C# syntax, that uses properties, constructors and the ToString() method to generate string representations of objects

class Rectangle
{
    double length;
    double width;

    public Rectangle(double length, double width)
    {
        this.length = length;
        this.width = width;
    }

    public double Length
    {
        get { return length; }
        set
        {
            length = value;
        }
    }
    public double Width
    {
        get { return width; }
        set
        {
            width = value;
        }
    }
    public double Area
    {
        get { return length * width; }
    }


    public override string ToString()
    {
        return $@"Length {Length}
Width {Width}
Area {Area}";
}

class ExecuteRectangle
{
    static void Main(string[] args)
    {
        Rectangle r = new Rectangle(4.5, 3.5);
        Console.WriteLine(r);
        //Length: 4.5
        //Width: 3.5
        //Area: 15.75

        r.Length = 6.5;
        Console.WriteLine(r);
        //Length: 6.5
        //Width: 3.5
        //Area: 22.75

        Console.ReadLine();
    }
}

I specifically made the properties mutable (can be changes) because this is a common design choice. If the properties were to be immutable then there wouldn't be a set method, and the fields would have a readonly keyword in front of them.

Upvotes: 1

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