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Could you please explain what is an Assembly in C# or .NET?
Where does it begin and where does it end?
What important information should I know about Assemblies?
An assembly is the compiled output of your code, typically a DLL, but your EXE is also an assembly. It's the smallest unit of deployment for any .NET project.
The assembly typically contains .NET code in MSIL (Microsoft Intermediate language) that will be compiled to native code ("JITted" - compiled by the Just-In-Time compiler) the first time it is executed on a given machine. That compiled code will also be stored in the assembly and reused on subsequent calls.
The assembly can also contain resources like icons, bitmaps, string tables and so on. Furthermore, the assembly also contains metadata in the assembly manifest - information like version number, strong name, culture, referenced assemblies and so forth.
In 99% of your cases, one assembly equals a physical file on disk - the case of a multi-file assembly (one assembly, distributed across more than a single file) appears to be a rather odd-ball edge case which I've never encountered so far in my 5+ years of .NET development.
In a multifile assembly there would still be only one assembly manifest in a DLL or EXE and the MSIL code in multiple netmodule files.
The answer is in order for immediate-grasping.
Put simply, it is the compiled project involving your classes and additional files, if there are. That is, each project in a
solution is assembly.
Or more techinally,
An assembly is where a type is stored in the flesystem. Assemblies are
a mechanism for deploying code. For example, the System.Data.dll
assembly contains types for managing data. To use types in other
assemblies, they must be referenced. - Source
How do we know it? If you glance at properties of a project under the solution you can see the following images.
When you compile the project, it turns out to DLL or EXE.
.NET assembly
In the Microsoft .NET framework, an
assembly is a partially compiled code
library for use in deployment,
versioning and security.
http://www.codeguru.com/columns/csharp_learning/article.php/c5845
An assembly is a file that is automatically generated by the compiler upon successful compilation of every .NET application. It can be either a Dynamic Link Library or an executable file. It is generated only once for an application and upon each subsequent compilation the assembly gets updated.
Here's another explanation of the make up of .NET Assemblies, a mini-quote:
The .NET framework consists of the
concepts of modules, assemblies, which
both store metadata and manifest
information. An assembly can contain
multiple modules. Visual C# only ever
creates one module which is turned
into an assembly by the C# compiler
(csc.exe), but an assembly can link
many .NET modules together via the
assembly linker (al.exe) command-line
tool. For example each of your source
code .cs files could be compiled into
a module and linked together to form
an assembly - an assembly is just a
collection of modules and resources.
One of these modules, however; must
contain manifest metadata (see below)
information for the assembly to be
understood by the CLR.
....
Having created a new .exe or .dll
inside VS.NET you see your file appear
inside your bin folder. Opening it in
notepad will give out gibberish, or
even inside a hexadecimal editor
without knowing the structure of the
file, you need a tool like ildasm.exe
or CFF explorer to make meaning from
it. The structure of the assembly is
as follows:
PE header
CLR header
CLR metadata
CLR
IL code
Native data
When a source code is compiled by the language compiler it Generate a Managed Assembly and MSIL(MisroSoft Intermediate Language). That Assembly contains .dll or .exe file. An Assebmly can be of two types Private Assembly and Shared Assembly, shared Assembly is stored in GAC(Global Assembly Cache) so that any application can refer to it while private assembly is stored in application folder which can be used by only one Application.
An assembly is a DLL or an EXE which will be created when you publish it or compile your application.
After writing source code of your program(project) then a file is created which may be DLL or EXE depends on your project. It makes only once for a single project. It has two types
1:- single
2:- shared or multiprogram
single assembly used only in a single program while shared can be used for multiprogram
An Assembly is a collection of logical units. Logical units refer to the types and resources which are required to build an application and deploy them using the .Net framework. Basically, Assembly is a collection of Exe and DLLs. It is portable and executable.
I have an app that references a .dll that was built with Costura/Fody i.e The dll has all its references embedded. When I run the console app, the references from the dll are not unpacked so the console app throws an exception saying missing .dll etc. as it needs those resources to run.
i.e. AssemblyA.dll embeds MyAssembly.dll when built with Costura/Fody. ConsoleAppC references and embeds AssemblyA.dll but also needs MyAssembly.dll to run. I do have a reference to MyAssembly.dll in ConsoleAppC so that it will compile (but CopyLocal is set to false). I was thinking that MyAssembly.dll would be made available to ConsoleAppC when AssemblyA.dll's embedded resources are unpacked?
This is not working but is my scenario valid in any way or can you only utilise embedded resources from ConsoleAppC and not the ones that were embedded in AssemblyA.dll?
Thanks in advance for any help
Mike
What you're trying to do isn't possible with Costura.Fody. What Costura does is embed libraries directly into the main assembly. This means that if you embed the built assembly into another project, it can't see the sub assemblies.
For example, consider the following project structure:
AssemblyA
Foo.cs
References:
SubAssembly1.dll
SubAssembly2.dll
SubAssembly3.dll
AssemblyB
Assume that Costura.Fody is used to embed the sub assemblies in AssemblyA, creating a single DLL file, AssemblyA.dll
If you embed AssemblyA.dll in AssemblyB, then you will not be able to access classes in SubAssembly1.dll. You will only be able to see any of the classes that are directly in AssemblyA.dll, such as those contained in Foo.cs - you will not be able to see any of the libraries referenced by/embedded in AssemblyA.dll.
See this answer to a similar question, where the answerer suggests using ILMerge instead.
Can any one will answer the following questions. I am using c# language.
Can I call Assembly as .ddl or .exe file?
Can I call Assembly Manifest as assembly?
What is different between Assembly, meta data and Assembly Manifest?
Can I say
.DLL or .EXE = Assembly + Meta Data + Assembly Manifest + MSIL CODE.
Please help me to clear these questions.
1 -- An assembly can be a single a .DLL or .EXE file, but not all .DLLs and .EXEs are assemblies. Assemblies are specific to the .NET framework. Both .EXE and .DLL assemblies can be referenced or loaded by your .NET application.
2 -- The assembly manifest is just one part of the assembly that contains metadata describing the assembly. From MSDN the assembly manifest:
Enumerates the files that make up the assembly.
Governs how references to the assembly's types and resources map to the files that contain their declarations and implementations.
Enumerates other assemblies on which the assembly depends.
Provides a level of indirection between consumers of the assembly and the assembly'simplementation details.
Renders the assembly self-describing.
You can add and change some aspects of the assembly manifest from your code if you need to change the metadata associated with that specific assembly. The assembly manifest may be stored as its own physical file, but it is still considered part of the assembly.
3 -- The assembly is composed of CIL code, metadata that describes the types defined by the CIL code, the assembly manifest which is metadata that describes the assembly and other resources such as static images needed by the assembly. Therefore, the assembly manifest is just one part of an assembly as is the metadata.
4 -- Almost. Assembly = MSIL Code + assembly manifest + type metadata + resources.
The assembly can be compiled into either an .EXE or .DLL file, but can also be comprised of multiple files.
Lets start with these concepts (in simple) then we will have our answers
Compilers are syntax checkers and “correct code” analyzers. in .Net platform regardless
of which compiler you use, the result is a managed module. A managed module is a standard
32-bit Microsoft Windows portable executable (PE32) file or a standard 64-bit Windows
portable executable (PE32+) file that requires the CLR to execute.
IL code Code the compiler produced as it compiled the source code. At
runtime, the CLR compiles the IL into native CPU instructions.
Metadata Every managed module contains metadata tables. There are two main
types of tables: tables that describe the types and members defined
in your source code and tables that describe the types and members
referenced by your source code.
Assembly is an abstract concept that can be difficult to grasp initially. First, an assembly is a logical grouping
of one or more modules or resource files. Second, an assembly is the smallest unit of reuse,security, and versioning. Depending on the choices you make with your compilers or tools,you can produce a single-file or a multifile assembly. In the CLR world, an assembly is what we would call a component.
(The CLR doesn’t actually work with modules, it works with assemblies)
Assembly Manifest is part of the assembly that describers set of files inside the assembly
An assembly allows you to decouple the logical and physical notions of a reusable, securable,versionable component. An assembly’s modules also include information about referenced assemblies (including their version numbers). This information makes an assembly self-describing. In other words, the CLR can determine the assembly’s immediate dependencies in order for code in the assembly to execute.
actually when using C# compiler, generatin .DLL Or .EXE will be done using a compiler option so DLL and EXE are equal components in assembly concepts.
So we will have
1- Correct, Assembly is Maneaged DDL(s) or EXE files
2- No, The assembly manifest is just part of the assembly
3- Described in the answer
4- Managed .DLL or .EXE = Assembly (Containing Meta Data + Assembly Manifest + MSIL CODE)
Images and some of the quotes from jeffrey richter
From the excellent book Pro C# 5 and the .NET 4.5 Framework:
When a *.dll or *.exe has been created using a .NET-aware compiler, the binary blob is termed an
assembly.
An assembly contains MSIL code, which is conceptually similar to Java bytecode in that
it is not compiled to platform-specific instructions until absolutely necessary.
Typically, “absolutely
necessary” is the point at which a block of MSIL instructions (such as a method implementation) is
referenced for use by the .NET runtime.
In addition to MSIL instructions, assemblies also contain metadata that describes in vivid detail the
characteristics of every “type” within the binary. For example, if you have a class named SportsCar, the
type metadata describes details such as SportsCar’s base class, which interfaces are implemented by
SportsCar (if any), as well as a full description of each member supported by the SportsCar type. .NET
metadata is always present within an assembly, and is automatically generated by a .NET-aware
language compiler.
Finally, in addition to MSIL and type metadata, assemblies themselves are also described using
metadata, which is officially termed a manifest. The manifest contains information about the current
version of the assembly, culture information (used for localizing string and image resources), and a list
of all externally referenced assemblies that are required for proper execution.
What are .NET Assemblies? I browsed over the net and I am not able to understand the definition.
Assembly is the smallest unit of deployment of a .net application.
It can be a dll or an exe.
There are mainly two types to it:
Private Assembly:
The dll or exe which is sole property of one application only. It is generally stored in application root folder
Public/Shared assembly:
It is a dll which can be used by multiple applications at a time. A shared assembly is stored in GAC i.e Global Assembly Cache.
Sounds difficult? Naa....
GAC is simply C:\Windows\Assembly folder where you can find the public assemblies/dlls of all the softwares installed in your PC.
There is also a third and least known type of an assembly: Satellite Assembly.
A Satellite Assembly contains only static objects like images and other non-executable files required by the application.
In more simple terms: A chunk of (precompiled) code that can be executed by the .NET runtime environment. A .NET program consists of one or more assemblies.
In addition to the accepted answer, I want to give you an example!
For instance, we all use
System.Console.WriteLine()
But Where is the code for System.Console.WriteLine!?
which is the code that actually puts the text on the console?
If you look at the first page of the documentation for the Console class, you‘ll see near the top the following: Assembly: mscorlib (in mscorlib.dll)
This indicates that the code for the Console class is located in an assem-bly named mscorlib. An assembly can consist of multiple files, but in this case it‘s only one file, which is the dynamic link library mscorlib.dll.
The mscorlib.dll file is very important in .NET, It is the main DLL for class libraries in .NET, and it contains all the basic .NET classes and structures.
if you know C or C++, generally you need a #include directive at the top that references a header file. The include file provides function prototypes to the compiler. on the contrast The C# compiler does not need header files. During compilation, the C# compiler access the mscorlib.dll file directly and obtains information from metadata in that file concerning all the classes and other types defined therein.
The C# compiler is able to establish that mscorlib.dll does indeed contain a class named Console in a namespace named System with a method named WriteLine that accepts a single argument of type string.
The C# compiler can determine that the WriteLine call is valid, and the compiler establishes a reference to the mscorlib assembly in the executable.
by default The C# compiler will access mscorlib.dll, but for other DLLs, you‘ll need to tell the compiler the assembly in which the classes are located. These are known as references.
I hope that it's clear now!
From DotNetBookZero Charles pitzold
Wikipedia has to say:
In the Microsoft .NET framework, an
assembly is a partially compiled code
library for use in deployment,
versioning and security. There are two
types: process assemblies (EXE) and
library assemblies (DLL). A process
assembly represents a process which
will use classes defined in library
assemblies. .NET assemblies contain
code in CIL, which is usually
generated from a CLI language, and
then compiled into machine language at
runtime by the CLR just-in-time
compiler. An assembly can consist of
one or more files. Code files are
called modules. An assembly can
contain more than one code module and
since it is possible to use different
languages to create code modules it is
technically possible to use several
different languages to create an
assembly. Visual Studio however does
not support using different languages
in one assembly.
If you really did browse it would help if you'd clarify what you don't understand
See this:
In the Microsoft .NET framework, an assembly is a partially compiled code library for use in deployment, versioning and security
physical collection of Class, interface, enum etc which is in IL code. Which can be .EXE or .DLL file .EXE is executable file and .DLL can dynamically used in any .net Supported language.
An assembly is a collection of types and resources that forms a logical unit of functionality. All types in the .NET Framework must exist in assemblies; the common language runtime does not support types outside of assemblies. Each time you create a Microsoft Windows® Application, Windows Service, Class Library, or other application with Visual Basic .NET, you're building a single assembly. Each assembly is stored as an .exe or .dll file.
Source : https://msdn.microsoft.com/en-us/library/ms973231.aspx#assenamesp_topic4
For those with Java background like me hope following diagram clarifies concepts -
Assemblies are just like jar files (containing multiple .class files). Your code can reference an existing assemblie or you code itself can be published as an assemblie for other code to reference and use (you can think this as jar files in Java that you can add in your project dependencies).
At the end of the day an assembly is a compiled code that can be run on any operating system with CLR installed. This is same as saying .class file or bundled jar can run on any machine with JVM installed.
MSDN has a good explanation:
Assemblies are the building blocks of .NET Framework applications; they
form the fundamental unit of
deployment, version control, reuse,
activation scoping, and security
permissions. An assembly is a
collection of types and resources that
are built to work together and form a
logical unit of functionality. An
assembly provides the common language
runtime with the information it needs
to be aware of type implementations.
To the runtime, a type does not exist
outside the context of an assembly.
In .Net, an assembly can be:
A collection of various manageable parts containing Types (or
Classes), Resources (Bitmaps/Images/Strings/Files), Namespaces,
Config Files compiled Privately or Publicly; deployed to a
local or Shared (GAC) folder; discover-able by other
programs/assemblies and; can be version-ed.
As assembly is the smallest unit of versioning security, deployment and reusability of code in Microsoft.Net.
It contains:
- Assembly Identity
- Manifest
- Metadata
- MSIL Code
- Security Information
- Assembly Header
Assembly is the fundamental part of programming with .NET Framework.
It contain code that CLR executes MSIL(Microsoft Intermediate Language) code in a portable executable file will not be executed if it does not have an associated assembly manifest.
In .NET, when we compile our source code then assembly gets generated in Visual Studio. Assembly consists of two parts Manifest and IL(Intermediate Language). Manifest contains assembly metadata means assembly's version requirements, security identity, names and hashes of all files that make up the assembly. IL contains information about classes, constructors, main method etc.
Visual Studio solutions consists of one or more projects. For Example : Console projects can produce an assembly. An assembly is logically chunk of code that can be shipped to customers, and physically an .EXE (executable program) or .DLL (are reusable by other programs).
What is considered as best practice when it comes to assemblies and releases?
I would like to be able to reference multiple versions of the same library - solution contains multiple projects that depend on different versions of a commonutils.dll library we build ourselves.
As all dependencies are copied to the bin/debug or bin/release, only a single copy of commonutils.dll can exist there despite each of the DLL files having different assembly version numbers.
Should I include version numbers in the assembly name to be able to reference multiple versions of a library or is there another way?
Assemblies can coexist in the GAC (Global Assembly Cache) even if they have the same name given that the version is different. This is how .NET Framework shipped assemblies work. A requirement that must be meet in order for an assembly to be able to be GAC registered is to be signed.
Adding version numbers to the name of the Assembly just defeats the whole purpose of the assembly ecosystem and is cumbersome IMHO. To know which version of a given assembly I have just open the Properties window and check the version.
Here's what I've been living by --
It depends on what you are planning to use the DLL files for. I categorize them in two main groups:
Dead-end Assemblies. These are EXE files and DLL files you really aren't planning on referencing from anywhere. Just weakly name these and make sure you have the version numbers you release tagged in source-control, so you can rollback whenever.
Referenced Assemblies. Strong name these so you can have multiple versions of it being referenced by other assemblies. Use the full name to reference them (Assembly.Load). Keep a copy of the latest-and-greatest version of it in a place where other code can reference it.
Next, you have a choice of whether to copy local or not your references. Basically, the tradeoff boils down to -- do you want to take in patches/upgrades from your references? There can be positive value in that from getting new functionality, but on the other hand, there could be breaking changes. The decision here, I believe, should be made on a case-by-case basis.
While developing in Visual Studio, by default you will take the latest version to compile with, but once compiled the referencing assembly will require the specific version it was compiled with.
Your last decision is to Copy Local or not. Basically, if you already have a mechanism in place to deploy the referenced assembly, set this to false.
If you are planning a big release management system, you'll probably have to put a lot more thought and care into this. For me (small shop -- two people), this works fine. We know what's going on, and don't feel restrained from having to do things in a way that doesn't make sense.
Once you reach runtime, you Assembly.Load whatever you want into the application domain. Then, you can use Assembly.GetType to reach the type you want. If you have a type that is present in multiple loaded assemblies (such as in multiple versions of the same project), you may get an AmbiguousMatchException exception. In order to resolve that, you will need to get the type out of an instance of an assembly variable, not the static Assembly.GetType method.
Giving different names to different assembly versions is the easiest way and surely works.
If your assembly (commonutils.dll) is strong-named (i.e. signed), you can think about installing it in the GAC (Global Assembly Cache - you can install different versions of the same assembly side-by-side in the GAC), therefore the calling application automatically gets the proper version from there because .NET Types include assembly version information.
In your VS project you reference the correct version of the library, but you don't deploy it in the application folder; you install it in the GAC instead (during application setup).