Assembly

nishant ranjan

14y1.8k.NET

What is Assembly? y Assembly? Cant we work without that? what is the need of assembly? y we use them?
Can any one explain me this in detail? i dont need the same bookish definition that it is fundamental unit of.....
plz if any one has simple detail idea/concept or any article then explain me.
thaks

13 Replies

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Vulpes14y ago
Accepted answer
Open up the Visual Studio command prompt, create a new directory and move to that directory:

md c:\myprograms

cd c:\myprograms

Now open up notepad with a file called hello.cs:

notepad hello.cs

type the following into the file and save it.

using System;

class Test
{
static void Main()
{
Console.WriteLine("Hello world!");
}
}

Now compile the file at the command line by typing this:

csc hello.cs

If you run the 'dir' command, you'll see that a file called hello.exe has been created in the same directory as hello.cs which is your executable assembly. You can direct the compiler to output the assembly anywhere you like using its /out switch.

You can now see what's in the assembly using a utility called ildasm.exe. Just type:

ildasm /text hello.exe

and you should see something similar to the following output:

// Microsoft (R) .NET Framework IL Disassembler. Version 4.0.30319.1
// Copyright (c) Microsoft Corporation. All rights reserved.

// 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 hello
{
.custom instance void [mscorlib]System.Runtime.CompilerServices.CompilationRel
axationsAttribute::.ctor(int32) = ( 01 00 08 00 00 00 00 00 )
.custom instance void [mscorlib]System.Runtime.CompilerServices.RuntimeCompati
bilityAttribute::.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.
.hash algorithm 0x00008004
.ver 0:0:0:0
}
.module hello.exe
// MVID: {404E0241-F629-4BE8-888D-6EBF59F10163}
.imagebase 0x00400000
.file alignment 0x00000200
.stackreserve 0x00100000
.subsystem 0x0003 // WINDOWS_CUI
.corflags 0x00000001 // ILONLY
// Image base: 0x004F0000

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

.class private auto ansi beforefieldinit Test
extends [mscorlib]System.Object
{
.method private hidebysig static void Main() cil managed
{
.entrypoint
// Code size 13 (0xd)
.maxstack 8
IL_0000: nop
IL_0001: ldstr "Hello world!"
IL_0006: call void [mscorlib]System.Console::WriteLine(string)
IL_000b: nop
IL_000c: ret
} // end of method Test::Main

.method public hidebysig specialname rtspecialname
instance void .ctor() cil managed
{
// Code size 7 (0x7)
.maxstack 8
IL_0000: ldarg.0
IL_0001: call instance void [mscorlib]System.Object::.ctor()
IL_0006: ret
} // end of method Test::.ctor

} // end of class Test

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

// *********** DISASSEMBLY COMPLETE ***********************

You'd need to read a specialist book or consult a number of online articles to understand what all this means but it will give you some idea of the amount of info that is generated during the compilation process.
nishant ranjan14y ago
Thanks a lot ... it cleared the concept a lot. thanks for being so supportive and patient.
Cheers!!
nishant ranjan14y ago
@vulpes: [Every time you successfully compile a .NET program, you create an assembly]
so where it is loaded/stored. and what is location path of private assembly. how can i view it
Vulpes14y ago
Every time you successfully compile a .NET program, you create an assembly. The compiler converts your source code to CIL, generates metadata for all the types used in the program and packages it up into an .exe or .dll file, depending on whether it's an executable or class library.

When you run a .NET executable, the operating system first looks at the file header and loads the approporiate version of the CLR which then loads the executable itself and runs it. Any libraries which the executable needs to run are loaded into the process's address space as needed.

The Global Assembly Cache (or GAC) is a central repository for storing .NET assemblies on a particular machine. It contains all the .dlls which comprise the .NET Framework plus any others you choose to install in there, though only rarely will you want to store your own dlls in the GAC.
nishant ranjan14y ago
@vulpes: okie. so it chooses assembly(from GAC) as per requirement. and is it true that every file which we compile/run is converted to assembly???
Vulpes14y ago
That's correct, Nishant.

The CLR needs everything contained in an assembly (CIL, metadata etc) to both launch it and manage it whilst it's running.
nishant ranjan14y ago
@vulpes: means all that assembly is just needed by clr. for clr to work we need assembly. m i right? means all info required by clr are contained in assembly.
Vulpes14y ago
It's just the way that .NET works.

Microsoft wanted something that was similar to Java and allowed you to program in different languages. To achieve that the various language compilers (C#, VB.NET etc) all had to produce an intermediate byte code which could then be turned into native code by the runtime.

They wanted programming to be simple by enabling the runtime to deal automatically with 'house-keeping' such as memory allocation, garbage collection and security issues so that the programmer could concentrate on the task in hand.

They also wanted to get rid of something called 'Dll Hell' which plagued unmanaged applications at the time by building in support for versioning.

.NET code is normally slower than unmanaged code written in C/C++ and there's an initial delay whilst the CLR is loaded. However, in most types of applications, the difference in speed is unimportant.
nishant ranjan14y ago
@vulpes: okie... but where its use... means when and how or for what reason we are using it. y we create assembly... just b'cause it contain all those as you mentioned) for fast execution
Vulpes14y ago
No, an assembly is either an executable (you can run it independently) or a class library (it can't be run independently). In that respect, it's just like an 'ordinary' windows application.

However, they decided to call it an assembly because there are a number of differences between it and ordinary windows applications. For example:

1. An assembly contains CIL (common intermediate language) rather than native code. The CLR (Common Language Runtime) takes this CIL and compiles it to native code dynamically.

2. An assembly can (though seldom does) consist of one or more files or 'modules' as they are called.

3. An assembly contains metadata as well as code and can also contain versioning information.
nishant ranjan14y ago
@Vulpes: means it is just a library..... application that acts as a library.
where its use comes.... how m calling those assembly file and for what purposes....
Vulpes14y ago
In simple terms an assembly is just a .NET application.

It can either be an executable (.exe) or a class library (.dll). The difference between these is that an executable needs an entry point - a Main() method - but a class library does not.

A class library provides classes which executables or other libraries can use. The .NET framework itself is just a collection of class libraries.

For most purposes that's all you need to know but, if you need to know more, the links which Satyapriya has given should be consulted.
Satyapriya Nayak14y ago
Hi Nishant,

Please refer the below links

http://www.c-sharpcorner.com/UploadFile/thiru_ji/1DotnetAssemblies02212007050300AM/1DotnetAssemblies.aspx

http://www.codeproject.com/Articles/20565/Assembly-Manipulation-and-C-VB-NET-Code-Injection

http://www.codeproject.com/Articles/3262/A-NET-assembly-viewer

http://www.codeproject.com/Articles/8874/Strong-Names-Explained

Thanks