Let’s create an extension SDK with two components. To avoid name collisions with other components, you should add your company name to the start of each component name, followed by a period.

Tip
You can use multiple words separated by periods, for example Fabrikam.Systems.Ultimate.Controls.DataGrid.Cell.dll

1. Open Visual Studio. Accept the software license terms and the UAC prompt if you see them.

2. Create a new Visual C# Windows Class Library for Tailored Applications project named MyCompany.Alpha.

3. Add a new Visual C# Windows Class Library for Tailored Applications project named MyCompany.Beta.

4. In the Solution Explorer, choose Show All Files for each project node. Examine the bin/Release folders and verify that you’ve built two managed assemblies.

You can combine your two assemblies into an extension SDK and install it to your machine this way:

1. Navigate to the folder

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   C:\Program Files\Microsoft SDKs\Windows\v8.0\ExtensionSDKs
   

2. Create a new subfolder named MyCompany.Extension.

3. Create a new subfolder in this folder named by the version number of your extension, for example, 1.0:

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   MyCompany.Extension\1.0
   

4. Create a new manifest text file named SDKManifest.xml on your desktop.

   Tip
   Your text editor can’t directly edit files in the Program File folder.

5. Fill the manifest file with the following xml:

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   <?xml version="1.0"?>
   <FileList AppliesTo="TailoredC#,TailoredVB"
       MinToolsVersion="4.0" MinVSVersion="11.0" 
       DisplayName="Brand name of extension"> 
       <File Reference="MyCompany.Alpha.dll"/> 
       <File Reference="MyCompany.Beta.dll"/> 
   </FileList>
   

   This roughly translates to “This extension requires Visual Studio 11.0 or later and .Net Framework 4.0 or later. It can be used by Visual C# or Visual Basic Metro style apps. The extension version is 1.0 and the name that appears in the Add Reference dialog is Brand name of extension. The extension consists of two files, both of which are managed DLLs.”

6. Copy the manifest file to the version subfolder

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   MyCompany.Extension\1.0\SDKManifest.xml
   

7. Create a new subfolder named References in the version folder

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   MyCompany.Extension\1.0\References
   

8. Create a new subfolder named CommonConfiguration in the References folder

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   MyCompany.Extension\1.0\References\CommonConfiguration
   

9. Create a new subfolder named neutral in the CommonConfiguration folder

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   MyCompany.Extension\1.0\References\CommonConfiguration\neutral
   

10. Copy the MyCompany.Alpha and MyCompany.Beta assemblies to the neutral folder.

The CommonConfiguration folder indicates that regardless of the configuration being targeted by the project consuming your SDK, you always want the references in this folder to be used. To limit the extension to a release configuration, name the folder Retail. To limit it to a debug configuration, name it Debug.

The neutral folder indicates that your extension can be used for apps built for Any CPU.

Caution
Actually, folders are examined in order from the least specific to the most specific: \commonconfiguration\neutral \commonconfiguration\[arch] \[config]\neutral \[config]\[arch] By putting your assemblies in the least specific folder, you do not have to put the same assembly in two folders.