Getting started with C# Language
C# is a multi-paradigm, C-descendant programming language from Microsoft. C# is a managed language that compiles to CIL, intermediate bytecode which can be executed on Windows, Mac OS X and Linux.
Versions 1.0, 2.0 and 5.0 were standardized by ECMA (as ECMA-334), and standardization efforts for modern C# are underway.
Creating a new console application (Visual Studio)
- Open Visual Studio
- In the toolbar, go to File → New Project
- Select the Console Application project type
- Open the file
Program.csin the Solution Explorer
- Add the following code to
- In the toolbar, click Debug -> Start Debugging or hit F5 or ctrl + F5 (running without debugger) to run the program.
class Programis a class declaration. The class
Programcontains the data and method definitions that your program uses. Classes generally contain multiple methods. Methods define the behavior of the class. However, the
Programclass has only one method:
static void Main()defines the
Mainmethod, which is the entry point for all C# programs. The
Mainmethod states what the class does when executed. Only one
Mainmethod is allowed per class.
System.Console.WriteLine("Hello, world!");method prints a given data (in this example,
Hello, world!) as an output in the console window.
System.Console.ReadKey(), ensures that the program won't close immediately after displaying the message. It does this by waiting for the user to press a key on the keyboard. Any key press from the user will terminate the program. The program terminates when it has finished the last line of code in the
Using the command line
To compile via command line use either
csc.exe (the C# compiler), both part of the Microsoft Build Tools package.
To compile this example, run the following command in the same directory where
HelloWorld.cs is located:
It can also be possible that you have two main methods inside one application. In this case, you have to tell the compiler which main method to execute by typing the following command in the console.(suppose Class
ClassA also has a main method in the same
HelloWorld.cs file in HelloWorld namespace)
%WINDIR%\Microsoft.NET\Framework64\v4.0.30319\csc.exe HelloWorld.cs /main:HelloWorld.ClassA
where HelloWorld is namespace
Note: This is the path where .NET framework v4.0 is located in general. Change the path according to your .NET version. In addition, the directory might be framework instead of framework64 if you're using the 32-bit .NET Framework. From the Windows Command Prompt, you can list all the csc.exe Framework paths by running the following commands (the first for 32-bit Frameworks):
There should now be an executable file named
HelloWorld.exe in the same directory. To execute the program from the command prompt, simply type the executable's name and hit Enter as follows:
This will produce:
You may also double click the executable and launch a new console window with the message "Hello, world!"
Creating a new program using .NET Core
First install the .NET Core SDK by going through the installation instructions for the platform of your choice:
After the installation has completed, open a command prompt, or terminal window.
Create a new directory with
mkdir hello_worldand change into the newly created directory with
Create a new console application with
dotnet new console.
This will produce two files:
Restore the needed packages with
Optional Build the application with
dotnet buildfor Debug or
dotnet build -c Releasefor Release.
dotnet runwill also run the compiler and throw build errors, if any are found.
Run the application with
dotnet runfor Debug or
dotnet run .\bin\Release\netcoreapp1.1\hello_world.dllfor Release.
Command Prompt output
Creating a new program using Mono
Mono is available for Mac OS X, Windows and Linux.
After installation is done, create a text file, name it
HelloWorld.cs and copy the following content into it:
If you are using Windows, run the Mono Command Prompt which is included in the Mono installation and ensures that the necessary environment variables are set. If on Mac or Linux, open a new terminal.
To compile the newly created file, run the following command in the directory containing
mcs -out:HelloWorld.exe HelloWorld.cs
HelloWorld.exe can then be executed with:
which will produce the output:
Hello, world! Press any key to exit..
Creating a new project in Visual Studio (console application) and Running it in Debug mode
Download and install Visual Studio. Visual Studio can be downloaded from VisualStudio.com. The Community edition is suggested, first because it is free, and second because it involves all the general features and can be extended further.
Open Visual Studio.
Click Templates → Visual C# → Console Application
After selecting Console Application, Enter a name for your project, and a location to save and press OK. Don't worry about the Solution name.
Project created. The newly created project will look similar to:
(Always use descriptive names for projects so that they can easily be distinguished from other projects. It is recommended not to use spaces in project or class name.)
Write code. You can now update your
Program.csto present "Hello world!" to the user.
Add the following two lines to the
public static void Main(string args)object in
Program.cs: (make sure it's inside the braces)
Console.Read()? The first line prints out the text "Hello world!" to the console, and the second line waits for a single character to be entered; in effect, this causes the program to pause execution so that you're able to see the output while debugging. Without
Console.Read();, when you start debugging the application it will just print "Hello world!" to the console and then immediately close. Your code window should now look like the following:
Debug your program. Press the Start Button on the toolbar near the top of the window or press F5 on your keyboard to run your application. If the button is not present, you can run the program from the top menu: Debug → Start Debugging. The program will compile and then open a console window. It should look similar to the following screenshot:
- Stop the program. To close the program, just press any key on your keyboard. The
Console.Read()we added was for this same purpose. Another way to close the program is by going to the menu where the Start button was, and clicking on the Stop button.
Creating a new project using Xamarin Studio
- Download and install Xamarin Studio Community.
- Open Xamarin Studio.
- Click File → New → Solution.
- Click .NET → Console Project and choose C#.
- Click Next to proceed.
- Enter the Project Name and Browse... for a Location to Save and then click Create.
- The newly created project will look similar to:
- This is the code in the Text Editor:
- To run the code, press F5 or click the Play Button as shown below:
- Following is the Output:
Creating a new query using LinqPad
LinqPad is a great tool that allows you to learn and test features of .Net languages (C#, F# and VB.Net.)
Type the following code and hit run (F5)
- You should see "Hello World" printed out in the results screen.
- Now that you have created your first .Net program, go and check out the samples included in LinqPad via the "Samples" browser. There are many great examples that will show you many different features of the .Net languages.
- If you click on "IL", you can inspect the IL code that your .net code generates. This is a great learning tool.
- When using
LINQ to SQLor
Linq to Entitiesyou can inspect the SQL that's being generated which is another great way to learn about LINQ.