CategoryManage assemblies

WinMD Assembly

Windows 8 introduced WinRT(Windows Runtime) that allows us to develop applications based on C++, C#, Vb and JavaScript by allowing access to its Api and by allowing communication between different programming languages. Communication between languages is possible through Windows Runtime Component that creates WinMD Assembly. WinMD Assembly is a Assembly that contains metadata but can also contain types.

When you try to create Windows 8.1 store app you cannot add usual Class Library, you have to add Windows Runtime Component and there you can write your usual code.

Trying to add Class library to your Store App will result in “Unable to add a reference to project” error.

WinMD limitations (copied from

  • The fields, parameters, and return values of all the public types and members in your component must be WinRT types.
  • Public structures may not have any members other than public fields, and those fields must be value types or strings.
  • Public classes must be sealed. If your programming model requires polymorphism, you can create a public interface and implement that interface on the classes that must be polymorphic. The only exceptions are XAML controls.
  • All public types must have a root namespace that matches the assembly name, and the assembly name must not begin with “Windows.”

Why would I need to create WinMD class library?

Lets explore it through Windows store app example.

Create new Solution and there add two Blank App.s for Windows 8.1 (one for C# and another for JS).

Both of these apps should have:

2x Textbox

1x Label

2x Button

Goal of this Application is to create Application where you can input data inside two different TextBoxes and combine their values inside Label after clicking button. Second goal is to copy some text value in your clipboard(simply copy some text with Ctrl+C) and display value in Label after clicking second button.

All this code can be easily achieved by writing it in backend of MainPage.xaml.cs file or inside JavaScript function, but we want our Application to share code, and that is here WinMD steps in. You can create methods that perform that actions and reuse it across different applications and different languages. Yup, even JavaScript can use WinMD classes written in C#.

Example of WinMD / Windows Runtime Component Assembly



MainPage.xaml.cs – Buttons

Windows Runtime Component – Helper class

If you wish to inspect entire solution , download it from this link.

Please do not use code from solution  for your projects because no checks were implemented what so ever.


GAC (Global Assembly Cache)

You can locate GAC folder inside Windows directory. GAC folder contains only strongly named assemblies. All applications that are running on your machine can access GAC folder and use its assemblies. Benefits of storing strongly named assemblies inside GAC are:

  • There is no need to distribute that particular assembly with every new version of application
  • Assemblies stored in GAC folder are strongly named so you need not to worry about having two or more version of same assembly distributed.

How can i locate GAC folder?

There are actually two locations:

  1. Location for assemblies created with .Net Framework 2.0 to .Net Framework 3.5
  2. Location for assemblies created with .Net Framework 4.0 and newer

Usually you cal locate it by typing C:\Windows\assembly for older strongly named assemblies or C:\Windows\Microsoft.NET\assembly for newer strongly named assemblies.

If your machine is not installed on C drive or your windows folder is not named Windows simply type in File explorer : %WINDIR%\Assembly or %WINDIR%\Microsoft.NET\assembly and you there you can find GAC folder.

How to install Strongly named assembly inside Global Assembly Cache?

Add new Class library project to Solution and name it AssemblyToInstall and strong name it.

Drag and drop approach:

Just simple locate bin\Debug folder inside AssemblyToInstall project, locate AssemblyToInstall.dll file and drop it to appropriate location (C:\Windows\Microsoft.NET\assembly). Note that you can do this only if your user has elevated privileges.

Using GacUtil.exe

If you are using Visual Studio 2013 or 2015 version, you can search for Developer Command Prompt and run it as Administrator.

New console will open.

Navigate to project. Mine is located on D drive under charp folder

Next you will need to run gacutil toll with -i parameter (basically -i switch is telling gacutil that we want to install assembly) followed by Assembly dll we want to install.

run command: gacutil.exe -i AssemblyToInstall.dll


How to use gacutil to install strongly named assembly inside GAC folder

You should receive message: “Assembly successfully added to the cache”

If you receive message: “Failure adding assembly to the cache: Attempt to install an assembly without a strong name”. That means that you have not signed assembly.

Now navigate to %WINDIR%\Microsoft.NET\assembly\GAC_MSIL\AssemblyToInstall and there you can see your assembly and can use that path to provide reference to that assembly to all applications located on this machine.

Tomorrow we will continue with topic on how to implement side-by-side hosting.

Strongly named assemblies

Purpose of strong naming assemblies is to create unique identity for desired assembly. You would typically want to do that when you need multiple versions of same assembly to be used, when assembly must be installed inside GAC (global assembly cache) or when you want assemblies to be to be referenced by strongly named assemblies.

What does it mean to be strongly named?

Strongly named assemblies are assemblies that have:

Name (usually name of project)

AssemblyVersion (AssemblyVersion information)

Culture information (Assemblies are usually culture neutral but if you wish to change them you can access AssemblyInfo.cs file and change AssemblyCulture attribute)

Private/Public key token (main difference between strongly named assemblies and weakly named assemblies)

I wish to create strongly named assemblies! What do i do?

First you would create a project. That first step would create weakly named assembly. Next what you want to do is sign it. There are multiple ways to achieve this.

First Approach:

From Visual studio:

  1. Right click project
  2. Properties
  3. Select Signing tab
  4. Check “Sign the assembly” CheckBox
  5. From Drop-down control select New
  6. Input necessary Information
  7. Select Drop-down control again and find your  .pfx file

Strongly named assemblies

How to strongly name assemblies

Now when we know how to strong name assemblies we can continue to part on how to put an assembly in the global assembly cache.



Version assemblies

When talking about Version assemblies you would usually interact with AssemblyVersion, AssemblyFileVersion, AssemblyInformationalVersion Atrributes. Ability to successfully version assemblies is important while testing, debugging and deploying your assemblies. Why? Because it allows you and your team to inspect and debug same version of assemblies on one hand and to know what version of assemblies is are your customers using when talking about future requirements and current problems.

AssemblyVersion and AssemblyFileVersion


Can be manually located in your Solution explorer:


AssemblyInfo.cs file you can manually change values of a few Attributes. But now we will take look at AssemblyVersion and AssemblyFileVersion attributes. Both these Attributes provide default value in string format. Default values  should appear like this when you initially create project:

Number values inside string have specific meaning:

  1. value -> major value. Value should be changed when changes to your program are noticeable, like major User interface and under the hood changes
  2. value -> minor. increment this value when adding new capabilities to your Application.
  3. value -> build number. Obviously this value should be incremented when running a build
  4. value -> revision. Value that you should increment when choosing which build version to deploy

Build number and revision can be automated by using asterisk(*). Just change strings too look like this and their values will be incremented automatically after each build:

If you are developing small scale application it is best to change minor and major values manually.

AssemblyVersion attribute is used by other assemblies. When value of this attribute is changed, all assemblies that reference it must change value to match current value to ensure that communication between them will proceed uninterrupted.

AssemblyFileVersion attribute is used for deployment (when you ship assemblies to end user). You always need to know which version of assembly is shipped to your customer so that you can assist them, detect bugs and plan future changes.


Usually you would not like to bore or even worse scare customers by displaying version of your Application in format like 8.56.7520.1459. You will want to display assembly version in user friendly format like 8.56 RC or 8 Orange, or any other format that will appeal to end user. This is where AssemblyInformationalVersion steps in. We can declare AssemblyInformationalVersion inside AssemblyInfo.cs file.

Nice. Please show me how to access these values.

First of. make sure that your AssemblyInfo.cs files has following values:

And inside main Method put following code:

This post has thought you how to version assemblies and was first post in Manage assemblies topic. Now we will continue to topic on how to strong name your assembly.

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