Generic Class With Main Method in c#

Question

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Why there is error can some one explain some reason i will be very thankful to you .

C#

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace GenericWithMainMethod
{
    class Program<T>
    {
        public void Dispaly() {

            Console.WriteLine("Why its happen.");

        }
        static void Main(string[] args)
        {

        }
    }
}

THE ERROR IS

Error 1 Program GenericWithMainMethod\obj\x86\Debug\GenericWithMainMethod.exe' does not contain a static 'Main' method suitable for an entry point GenericWithMainMethod

Posted 29-Oct-14 18:41pm

siddharth629

Updated 29-Oct-14 18:52pm

v2

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Laiju k 30-Oct-14 0:48am

what was the error be specific

siddharth629 30-Oct-14 0:52am

Error 1 Program 'GenericWithMainMethod\GenericWithMainMethod\obj\x86\Debug\GenericWithMainMethod.exe' does not contain a static 'Main' method suitable for an entry point GenericWithMainMethod

PIEBALDconsult 30-Oct-14 0:48am

Well? What error?

siddharth629 30-Oct-14 0:53am

Error 1 Program 'GenericWithMainMethod\GenericWithMainMethod\obj\x86\Debug\GenericWithMainMethod.exe' does not contain a static 'Main' method suitable for an entry point GenericWithMainMethod

Laiju k 30-Oct-14 1:15am

static void Main(string[] args)
{

}
remove this from code

Philippe Mori 30-Oct-14 22:20pm

Main is incompatible with Generic class. You'll have to create a non generic class for the entry point.

Although it might probably be feasible to support that, it would give no real benefinit so don't expect to see that in future versions of the compiler.

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PIEBALDconsult · Accepted Answer · 2014-10-29T18:51:00

One thing you need to remember about generic classes in .net is that they don't really exist until you provide the type -- to make a concrete class.

As it stands, the compiler doesn't have enough information. Even to access static members (as with your Main), you must specify the type.

One of the important things about static members in generic types, is that they are not shared by different concrete types made from the same generic type. In your case, that means the runtime has no way to call Main.

Have a look at this:
error CS0402: Warning as Error: 'GenericWithMainMethod.Program<t>.Main(string[])': an entry point cannot be generic or in a generic type

http://msdn.microsoft.com/en-us/library/ht5h7yhs(v=vs.90).aspx[^]

This might (or might not) help understand:

XML

# pragma warning disable 0402

namespace GenericWithMainMethod
{
    class Program<T>
    {
        private static System.Type type = typeof(T) ;

        public void Dispaly()
        {
            System.Console.WriteLine("I am a {0}" , type );
        }

        /* this causes warning 0402 */
        public static void Main(string[] args)
        {
          (new Program<T>()).Dispaly() ;
        }
    }

    class C
    {
        static void Main(string[] args)
        {
          Program<int>.Main(null) ;
          Program<string>.Main(null) ;

          System.Console.ReadLine() ;
        }
    }
}

What were you trying to do?

BillWoodruff · Accepted Answer · 2014-10-29T19:38:00

You are ignoring the fact that for both .NET Console Applications, and WinForms Apps, a Class named 'Program ... which is not generic ... is a special construction used to tell the compiler how to start the Application.

In the case of a Console Application created in Visual Studio using File/New/Project => select ConsoleApplication, the Program Class is not marked 'static, and 'Main is written:

C#

class Program
{
    static void Main(string[] args)
    {
    }
}

When you create a new WinForm Project using File/New/Project => select Windows Forms Application:

C#

static class Program
{
    [STAThread]
    static void Main()
    {
    }
}

It is possible to remove the 'static modifier from the WinForms Program Class and still have a working program.

In the case of a Console App you can change the declaration of the Program Class to 'static and it will still run.

However, I cannot see any reason why anyone would ever want to modify the default declarations of a WinForms app 'Program Class to non-static, or a Console app Program Class to static !

Your creating a generic Program<> class is just ... a mistake. And, in this case, you make no use of the generic Type you specify.

What were you really trying to achieve here: to add one method to the 'Program class ?

Generic Class With Main Method in c#

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