Global Attributes in Visual Basic

Most attributes are attached to specific language elements such as classes or methods. However, some attributes are global—they can apply to a whole assembly or module.

You can set many of the attributes in the Visual Studio Integrated Development Environment (IDE) through the Assembly Information Dialog Box. For more information, see Managing Application Properties and Managing Assembly and Manifest Signing.

Assembly Attributes

You specify assembly-level attributes by using the following syntax:

<Assembly: Attribute1, Assembly: Attribute2..., Assembly: AttributeN>

You specify module-level attributes by using similar syntax:

<Module: Attribute1, Module: Attribute2..., Module: AttributeN>

You add global attributes in source code after any top-level directives, such as Option Explicit and Imports statements, but before any type or namespace declarations. Global attributes can appear in multiple source files in a project, but they are generally put in the file AssemblyInfo.vb file created automatically with Visual Basic projects.

Assembly attributes are values that provide information about an assembly. They fall into the following categories:

• Assembly identity attributes

• Informational attributes

• Assembly manifest attributes

• Strong name attributes

Assembly Identity Attributes

Three attributes (with a strong name, if applicable) determine the identity of an assembly: name, version, and culture. These attributes form the full name of the assembly and are required when you reference it in code. You can set an assembly's version and culture using attributes. However, the name value is set by the compiler, the Visual Studio IDE in the Assembly Information Dialog Box, or the Assembly Linker (Al.exe) when the assembly is created, based on the file that contains the assembly manifest. The AssemblyFlagsAttribute attribute specifies whether multiple copies of the assembly can coexist.

The following table shows the identity attributes.

The following code applies the version and culture attributes to an assembly:

'Set version number for assembly.
<Assembly: Reflection.AssemblyVersionAttribute("4.3.2.1")> 
'Set culture as German.
<Assembly: Reflection.AssemblyCultureAttribute("de")> 

Informational Attributes

You can use informational attributes to provide additional company or product information for an assembly. The following table shows the informational attributes defined in the System.Reflection namespace.

Assembly Manifest Attributes

You can use assembly manifest attributes to provide information in the assembly manifest. This includes title, description, default alias, and configuration. The following table shows the assembly manifest attributes defined in the System.Reflection namespace.

Strong Name Attributes

Strong names are unique identifiers that protect the identity and integrity of an assembly. You can sign an assembly from the Visual Studio IDE through the Signing Page, Project Designer. For more information, see Managing Assembly and Manifest Signing.

Alternatively, you can use strong-name attributes to set a strong name for an assembly. The following table shows the strong-name attributes defined in the System.Reflection namespace.

If the KeyFile and the KeyName values are both specified, the following processing occurs:

• If the KeyName can be found in the CSP, that key is used.

• If the KeyName does not exist and the KeyFile does exist, the key in the KeyFile is installed into the CSP and used.

• For more information, see Assembly Security Considerations.

Signing Assemblies

You can sign an assembly in two different but complementary ways: with a strong name or with signing. You can sign using the Visual Studio IDE Signing Page, Project Designer or by using the File Signing Tool (Signcode.exe). When you sign an assembly with a strong name, it adds a public key encryption to the file that contains the assembly manifest. Strong-name signing helps verify name uniqueness, prevent name spoofing, and provide callers with some identity when a reference is resolved. For more information, see Managing Assembly and Manifest Signing and How to: Sign an Assembly with a Strong Name.

To sign an assembly with a strong name

1. Use the Strong Name Tool (Sn.exe) to generate a key file that contains a key pair.

2. Add strong name attributes to the AssemblyInfo.vb file created automatically with Visual Basic projects. To edit this file, double-click the file name in the Solution Explorer.

   The following example uses delay signing to create a strong-named assembly with a public key file that is named myKey.snk.

   <Assembly: Reflection.AssemblyKeyFile("myKey.snk")> 
   <Assembly: Reflection.AssemblyDelaySign(True)> 
   

   Note

   Assembly-level attributes are ignored if you do not create an assembly, such as when you compile from the command line by using the /target:module option.

See Also

Tasks

How to: Define Your Own Attributes

How to: Sign an Assembly with a Strong Name

Concepts

Application of Attributes

Assembly Security Considerations

Reference

Strong Name Tool (Sn.exe)

File Signing Tool (Signcode.exe)

Signing Page, Project Designer

Assembly Information Dialog Box

Other Resources

Custom Attributes in Visual Basic

Managing Application Properties

Managing Assembly and Manifest Signing