index.md

title	Main() and command-line arguments (C# Programming Guide)
ms.date	08/02/2017
ms.prod	.net
ms.technology	devlang-csharp
ms.topic	article
f1_keywords	CS5001 main_CSharpKeyword Main
helpviewer_keywords	Main method [C#] C# language, command-line arguments arguments [C#], command-line command line [C#], arguments command-line arguments [C#], Main method
ms.assetid	73a17231-cf96-44ea-aa8a-54807c6fb1f4
caps.latest.revision	30
author	BillWagner
ms.author	wiwagn

Main() and command-line arguments (C# Programming Guide)

The Main method is the entry point of a C# application. (Libraries and services do not require a Main method as an entry point.) When the application is started, the Main method is the first method that is invoked.

There can only be one entry point in a C# program. If you have more than one class that has a Main method, you must compile your program with the /main compiler option to specify which Main method to use as the entry point. For more information, see /main (C# Compiler Options).

[!code-csharpcsProgGuideMain#17]

Overview

• The Main method is the entry point of an executable program; it is where the program control starts and ends.
• Main is declared inside a class or struct. Main must be static and it need not be public. (In the earlier example, it receives the default access of private.) The enclosing class or struct is not required to be static.
• Main can either have a void, int, or, starting with C# 7.1, Task, or Task<int> return type.
• If and only if Main returns a Task or Task<int>, the declaration of Main may include the async modifier. Note that this specifically excludes an async void Main method.
• The Main method can be declared with or without a string[] parameter that contains command-line arguments. When using [!INCLUDEvsprvs] to create Windows applications, you can add the parameter manually or else use the xref:System.Environment class to obtain the command-line arguments. Parameters are read as zero-indexed command-line arguments. Unlike C and C++, the name of the program is not treated as the first command-line argument.

The addition of async and Task, Task<int> return types simplifies program code when console applications need to start and await asynchronous operations in Main.

C# language specification

[!INCLUDECSharplangspec]

See also

Command-line Building With csc.exe C# Programming Guide Methods Inside a C# Program