Csharp/C Sharp/Language Basics/Main

Deal with the arguments

<source lang="csharp"> using System; class SayHello {

   public static void Main(string[] args) {
       if (args.Length > 0) {
           foreach (string arg in args) {
               if (arg.Equals("/help"))
                   Console.WriteLine("Run this program as follows: sayhello.exe [name1] ");
               else
                   Console.WriteLine("Hello " + "{0}", arg);
           }
       } else
           Console.WriteLine("For help, run sayhello.exe /help");
   }

}

</source>

Every console app starts with Main

<source lang="csharp"> /* Learning C# by Jesse Liberty Publisher: O"Reilly ISBN: 0596003765

• /

namespace NotePad
{
   public class HelloWorld
   {
      // every console app starts with Main
      static void Main()
      {
         System.Console.WriteLine("Hello world!");
      }
   }
}

      </source>

Main Function: Multiple Mains

<source lang="csharp">

// error using System; class Complex {

   static int Main()
   {
       // test code here
       Console.WriteLine("Console: Passed");
       return(0);
   }

} public class TheMainFunctionMultipleMains {

   public static void Main(string[] args)
   {
       foreach (string arg in args)
       Console.WriteLine(arg);
   }

}

      </source>

Return different value to the operating system based on the argument length

<source lang="csharp"> using System; class SayHello {

   public static int Main(string[] args) {
       if (args.Length > 0) {
           foreach (string arg in args) {
               if (arg.Equals("/help")) {
                   Console.WriteLine("Run this program as follows:" +
                             "sayhello.exe [name1] ");
                   return (1);
               } else
                   Console.WriteLine("Hello " + "{0}", arg);
           }
           return (0);
       } else
           Console.WriteLine("For help, run sayhello.exe /help");
       return (2);
   }

}

</source>

Static Main function

<source lang="csharp"> /* Learning C# by Jesse Liberty Publisher: O"Reilly ISBN: 0596003765

• /

using System;
namespace StaticTester
{
    // create the class
   public class StaticTester
   {
      // Run is an instance method
      public void Run()
      {
          Console.WriteLine("Hello world");
      }
      // Main is static
      static void Main()
      {
          // create an instance
          StaticTester t = new StaticTester();
          // invoke the instance method
          t.Run();
      }
   }
}
          
      </source>

The Main Function

<source lang="csharp"> using System; public class TheMainFunction {

   public static void Main()
   {
       Console.WriteLine("Hello, Universe!");
   }

}

      </source>

The Main Function:Command-Line Parameters

<source lang="csharp">

using System; public class CommandLineParameters {

   public static void Main(string[] args)
   {
       foreach (string arg in args)
       Console.WriteLine("Arg: {0}", arg);
   }

}

      </source>

The Main Function:Returning an Int Status

<source lang="csharp">

using System; public class ReturninganIntStatus {

   public static int Main()
   {
       Console.WriteLine("Hello, Universe!");
       return(0);
   }

}

      </source>

This is a simple C# program

<source lang="csharp"> /* C#: The Complete Reference by Herbert Schildt Publisher: Osborne/McGraw-Hill (March 8, 2002) ISBN: 0072134852

• /

/*

  This is a simple C# program. 

  Call this program Example.cs. 

• /

using System;

public class ExampleWriteLine {

 // A C# program begins with a call to Main(). 
 public static void Main() { 
   Console.WriteLine("A simple C# program."); 
 } 

}

      </source>

Using command-line arguments to initialize an array.

<source lang="csharp"> using System; public class InitArray {

  public static void Main( string[] args )
  {
        int arrayLength = Convert.ToInt32( args[ 0 ] );
        int[] array = new int[ arrayLength ]; // create array
        int initialValue = Convert.ToInt32( args[ 1 ] );
        int increment = Convert.ToInt32( args[ 2 ] );
        for ( int counter = 0; counter < array.Length; counter++ )
           array[ counter ] = initialValue + increment * counter;
        Console.WriteLine( "{0}{1,8}", "Index", "Value" );
        for ( int counter = 0; counter < array.Length; counter++ )
           Console.WriteLine( "{0,5}{1,8}", counter, array[ counter ] );
  }

}

      </source>

Variations on the Main() Method

<source lang="csharp"> /* The previous iteration of Main() was defined to take a single parameter (an array of strings) and return an integer data type. This is not the only possible form of Main(), however. It is permissible to construct your application¡�s entry point using any of the following signatures (assuming it is contained within a C# class or structure definition): // No return type, array of strings as argument. public static void Main(string[] args) { } // No return type, no arguments. public static void Main() { } // Integer return type, no arguments. public static int Main() { }

• /

</source>