General Structure of a C# Program

C# programs consist of one or more files. Each file contains zero or more namespaces. A namespace contains types such as classes, structs, interfaces, enumerations, and delegates, or other namespaces. The following example is the skeleton of a C# program that contains all of these elements.

C#

using System;

Console.WriteLine("Hello world!");

namespace YourNamespace
{
    class YourClass
    {
    }

    struct YourStruct
    {
    }

    interface IYourInterface
    {
    }

    delegate int YourDelegate();

    enum YourEnum
    {
    }

    namespace YourNestedNamespace
    {
        struct YourStruct
        {
        }
    }
}

The preceding example uses top-level statements for the program's entry point. Only one file can have top-level statements. The program's entry point is the first line of program text in that file. In this case, it's the Console.WriteLine("Hello world!");. You can also create a static method named Main as the program's entry point, as shown in the following example:

C#

// A skeleton of a C# program
using System;
namespace YourNamespace
{
    class YourClass
    {
    }

    struct YourStruct
    {
    }

    interface IYourInterface
    {
    }

    delegate int YourDelegate();

    enum YourEnum
    {
    }

    namespace YourNestedNamespace
    {
        struct YourStruct
        {
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Hello world!");
        }
    }
}

In that case the program will start in the first line of Main method, which is Console.WriteLine("Hello world!");

Related Sections

You learn about these program elements in the types section of the fundamentals guide:

• Classes
• Structs
• Namespaces
• Interfaces
• Enums
• Delegates

C# Language Specification

For more information, see Basic concepts in the C# Language Specification. The language specification is the definitive source for C# syntax and usage.