What is the difference between C# and .NET?

May I know what is the difference between C# and .NET? When I think of C#, right away I would say it is a .NET language, but when I search for job posts, they require candidates to have C# and .NET experience. Can someone give me an explanation?

C# is a programming language, .NET is a blanket term that tends to cover both the .NET Framework (an application framework library) and the Common Language Runtime which is the runtime in which .NET assemblies are run.

Microsoft's implementation of C# is heavily integrated with the .NET Framework so it is understandable that the two concepts would be confused. However it is important to understand that they are two very different things.

Here is a class written in C#:

class Example { }

Here is a class written in C# that explicitly uses a .NET framework assembly, type, and method:

class Example
{
    static void Main()
    {
        // Here we call into the .NET framework to 
        // write to the output console
        System.Console.Write("hello, world");
    }
}

As I mentioned before, it is very difficult to use Microsoft's implementation of C# without using the .NET framework as well. My first Example implementation above even uses the .NET framework (implicitly, yes, but it does use it nonetheless) because Example inherits from System.Object.

Also, the reason I use the phrase Microsoft's implementation of C# is because there are other implementations of C# available.

In addition to Andrew's answer, it is worth noting that:

• .NET isn't just a library, but also a runtime for executing applications.
• The knowledge of C# implies some knowledge of .NET (because the C# object model corresponds to the .NET object model and you can do something interesting in C# just by using .NET libraries). The opposite isn't necessarily true as you can use other languages to write .NET applications.

The distinction between a language, a runtime, and a library is more strict in .NET/C# than for example in C++, where the language specification also includes some basic library functions. The C# specification says only a very little about the environment (basically, that it should contain some types such as int, but that's more or less all).

C# is a programming language, .NET is the framework that the language is built on.

C# is a strong Object Oriented programming language that is mostly built on the .NET framework.

C# is the airplane and .NET is the runway ;)

C# is a language, .NET is an application framework. The .NET libraries can run on the CLR and thus any language which can run on the CLR can also use the .NET libraries.

If you are familiar with Java, this is similar... Java is a language built on top of the JVM... though any of the pre-assembled Java libraries can be used by another language built on top of the JVM.

When people talk about the ".net framework" they tend to be combining two main areas - the runtime library and the virtual machine that actually runs the .net code.

When you create a class library in Visual Studio in C#, the DLL follows a prescribed format - very roughly, there is section that contains meta data that describes what classes are included in it and what functions they have, etc.. and that describes where in the binary those objects exist. This common .net format is what allows libraries to be shared between .net languages (C#, VB.Net, F# and others) easily. Although much of the .net "runtime library" is written in C# now (I believe), you can imagine how many of them could have been written in unmanaged languages but arranged in this prescribed format so that they could be consumed by .net languages.

The real "meat" of the library that you build consists of CIL ("Common Intermediate Language") which is a bit like the assembly language of .net - again, this language is the common output of all .net languages, which is what makes .net libraries consumable by any .net language.

Using the tool "ildasm.exe", which is freely available in Microsoft SDKs (and might already be on your computer), you can see how C# code is converted into meta data and IL. I've included a sample at the bottom of this answer as an example.

When you run execute .net code, what is commonly happening is the .net virtual machine is reading that IL and processing it. This is the other side of .net and, again, you can likely imagine that this could easily be written in an unmanaged language - it "only" needs to read VM instructions and run them (and integrate with the garbage collector, which also need not be .net code).

What I've described is (again, roughly) what happens when you build an executable in Visual Studio (for more information, I highly recommend the book "CLR via C# by Jeffrey Richter" - it's very detailed and excellently written).

However, there are times that you might write C# that will not be executed within a .net environment - for example, Bridge.NET "compiles" C# code into JavaScript which is then run in the browser (the team that produce it have gone to the effort of writing versions of the .net runtime library that are written in JavaScript and so the power and flexibility of the .net library is available to the generated JavaScript). This is a perfect example of the separation between C# and .net - it's possible to write C# for different "targets"; you might target the .net runtime environment (when you build an executable) or you might target the browser environment (when you use Bridge.NET).

A (very) simple example class:

using System;

namespace Example
{
	public class Class1
    {
		public void SayHello()
		{
			Console.WriteLine("Hello");
		}
    }
}

The resulting meta data and IL (retrieved via ildasm.exe):

// Metadata version: v4.0.30319
.assembly extern mscorlib
{
  .publickeytoken = (B7 7A 5C 56 19 34 E0 89 )                         // .z\V.4..
  .ver 4:0:0:0
}
.assembly Example
{
  .custom instance void [mscorlib]System.Runtime.CompilerServices.CompilationRelaxationsAttribute::.ctor(int32) = ( 01 00 08 00 00 00 00 00 ) 
  .custom instance void [mscorlib]System.Runtime.CompilerServices.RuntimeCompatibilityAttribute::.ctor() = ( 01 00 01 00 54 02 16 57 72 61 70 4E 6F 6E 45 78   // ....T..WrapNonEx
                                                                                                            63 65 70 74 69 6F 6E 54 68 72 6F 77 73 01 )       // ceptionThrows.

  // --- The following custom attribute is added automatically, do not uncomment -------
  //  .custom instance void [mscorlib]System.Diagnostics.DebuggableAttribute::.ctor(valuetype [mscorlib]System.Diagnostics.DebuggableAttribute/DebuggingModes) = ( 01 00 07 01 00 00 00 00 ) 

  .custom instance void [mscorlib]System.Reflection.AssemblyTitleAttribute::.ctor(string) = ( 01 00 0A 54 65 73 74 49 4C 44 41 53 4D 00 00 )    // ...TestILDASM..
  .custom instance void [mscorlib]System.Reflection.AssemblyDescriptionAttribute::.ctor(string) = ( 01 00 00 00 00 ) 
  .custom instance void [mscorlib]System.Reflection.AssemblyConfigurationAttribute::.ctor(string) = ( 01 00 00 00 00 ) 
  .custom instance void [mscorlib]System.Reflection.AssemblyCompanyAttribute::.ctor(string) = ( 01 00 00 00 00 ) 
  .custom instance void [mscorlib]System.Reflection.AssemblyProductAttribute::.ctor(string) = ( 01 00 0A 54 65 73 74 49 4C 44 41 53 4D 00 00 )    // ...TestILDASM..
  .custom instance void [mscorlib]System.Reflection.AssemblyCopyrightAttribute::.ctor(string) = ( 01 00 12 43 6F 70 79 72 69 67 68 74 20 C2 A9 20   // ...Copyright .. 
                                                                                                  20 32 30 31 36 00 00 )                            //  2016..
  .custom instance void [mscorlib]System.Reflection.AssemblyTrademarkAttribute::.ctor(string) = ( 01 00 00 00 00 ) 
  .custom instance void [mscorlib]System.Runtime.InteropServices.ComVisibleAttribute::.ctor(bool) = ( 01 00 00 00 00 ) 
  .custom instance void [mscorlib]System.Runtime.InteropServices.GuidAttribute::.ctor(string) = ( 01 00 24 31 39 33 32 61 32 30 65 2D 61 37 36 64   // ..$1932a20e-a76d
                                                                                                  2D 34 36 33 35 2D 62 36 38 66 2D 36 63 35 66 36   // -4635-b68f-6c5f6
                                                                                                  32 36 36 31 36 37 62 00 00 )                      // 266167b..
  .custom instance void [mscorlib]System.Reflection.AssemblyFileVersionAttribute::.ctor(string) = ( 01 00 07 31 2E 30 2E 30 2E 30 00 00 )             // ...1.0.0.0..
  .custom instance void [mscorlib]System.Runtime.Versioning.TargetFrameworkAttribute::.ctor(string) = ( 01 00 1C 2E 4E 45 54 46 72 61 6D 65 77 6F 72 6B   // ....NETFramework
                                                                                                        2C 56 65 72 73 69 6F 6E 3D 76 34 2E 35 2E 32 01   // ,Version=v4.5.2.
                                                                                                        00 54 0E 14 46 72 61 6D 65 77 6F 72 6B 44 69 73   // .T..FrameworkDis
                                                                                                        70 6C 61 79 4E 61 6D 65 14 2E 4E 45 54 20 46 72   // playName..NET Fr
                                                                                                        61 6D 65 77 6F 72 6B 20 34 2E 35 2E 32 )          // amework 4.5.2
  .hash algorithm 0x00008004
  .ver 1:0:0:0
}
.module Example.dll
// MVID: {80A91E4C-0994-4773-9B73-2C4977BB1F17}
.imagebase 0x10000000
.file alignment 0x00000200
.stackreserve 0x00100000
.subsystem 0x0003       // WINDOWS_CUI
.corflags 0x00000001    //  ILONLY
// Image base: 0x05DB0000

// =============== CLASS MEMBERS DECLARATION ===================

.class public auto ansi beforefieldinit Example.Class1
       extends [mscorlib]System.Object
{
  .method public hidebysig instance void 
          SayHello() cil managed
  {
    // Code size       13 (0xd)
    .maxstack  8
    IL_0000:  nop
    IL_0001:  ldstr      "Hello"
    IL_0006:  call       void [mscorlib]System.Console::WriteLine(string)
    IL_000b:  nop
    IL_000c:  ret
  } // end of method Class1::SayHello

  .method public hidebysig specialname rtspecialname 
          instance void  .ctor() cil managed
  {
    // Code size       8 (0x8)
    .maxstack  8
    IL_0000:  ldarg.0
    IL_0001:  call       instance void [mscorlib]System.Object::.ctor()
    IL_0006:  nop
    IL_0007:  ret
  } // end of method Class1::.ctor

} // end of class Example.Class1

// =============================================================

In .NET you don't find only C#. You can find Visual Basic for example. If a job requires .NET knowledge, probably it need a programmer who knows the entire set of languages provided by the .NET framework.

C# is a programming language.

.Net is a framework used for building applications on Windows.

.Net framework is not limited to C#. Different languages can target .Net framework and build applications using that framework. Examples are F# or VB.Net

C# does not have a seperate runtime library. It uses .NET as a runtime library.

Here I provided you a link where explain what is C# Language and the .NET Framework Platform Architecture. Remember that C# is a general-purpose, object-oriented programming language, and it runs on the .NET Framework.

.NET Framework includes a large class library named Framework Class Library (FCL) and provides user interface, data access, database connectivity, cryptography, web application development, numeric algorithms, and network communications.

.NET Framework was developed by Microsoft that runs primarily on Microsoft Windows.

Introduction to the C# Language and the .NET Framework from Microsoft Docs