AssemblyVersionAttribute Class

Definition

Namespace:

System.Reflection

Assembly:

System.Runtime.dll

Source:

AssemblyVersionAttribute.cs

Specifies the version of the assembly being attributed.

public ref class AssemblyVersionAttribute sealed : Attribute

[System.AttributeUsage(System.AttributeTargets.Assembly, Inherited=false)]
public sealed class AssemblyVersionAttribute : Attribute

[<System.AttributeUsage(System.AttributeTargets.Assembly, Inherited=false)>]
type AssemblyVersionAttribute = class
    inherit Attribute

Public NotInheritable Class AssemblyVersionAttribute
Inherits Attribute

Inheritance

Object

Attribute

AssemblyVersionAttribute

Attributes

AttributeUsageAttribute

Examples

The following example uses the AssemblyVersionAttribute attribute to assign a version number to an assembly. At compile time, this version information is stored with the assembly's metadata. At run time, the example retrieves the value of the Type.Assembly property on a type found in the assembly to get a reference to the executing assembly, and it retrieves the assembly's version information from the Version property of the AssemblyName object returned by the Assembly.GetName method.

using System;
using System.Reflection;

[assembly:AssemblyVersionAttribute("2.0.1")]

public class Example1
{
   public static void Main()
   {
      Assembly thisAssem = typeof(Example1).Assembly;
      AssemblyName thisAssemName = thisAssem.GetName();
       
      Version ver = thisAssemName.Version;
       
      Console.WriteLine("This is version {0} of {1}.", ver, thisAssemName.Name);    
   }
}
// The example displays the following output:
//        This is version 2.0.1.0 of Example1.

Imports System.Reflection

<Assembly:AssemblyVersionAttribute("2.0.1")>
Module Example1
   Public Sub Main()
       Dim thisAssem As Assembly = GetType(Example1).Assembly
       Dim thisAssemName As AssemblyName = thisAssem.GetName()
       
       Dim ver As Version = thisAssemName.Version
       
       Console.WriteLine("This is version {0} of {1}.", ver, thisAssemName.Name)    
   End Sub
End Module
' The example displays the following output:
'      This is version 2.0.1.0 of Example1.

Remarks

The AssemblyVersionAttribute attribute is used to assign a version number to an assembly. That version number is then stored with the assembly's metadata.

The assembly version number is part of an assembly's identity and plays a key part in binding to the assembly and in version policy. The default version policy for the runtime is that applications run only with the versions they were built and tested with, unless overridden by explicit version policy in configuration files (the application configuration file, the publisher policy file, and the computer's administrator configuration file). See Assemblies in .NET for more information.

Note

Version checking only occurs with strong-named assemblies.

The version number has four parts, as follows:

<major version>.<minor version>.<build number>.<revision>

Important

All components of the version must be integers greater than or equal to 0. Metadata restricts the major, minor, build, and revision components for an assembly to a maximum value of UInt16.MaxValue - 1. If a component exceeds this value, a compilation error occurs.

For example, [assembly:AssemblyVersion("2.3.25.1")] indicates 2 as the major version, 3 as the minor version, 25 as the build number, and 1 as the revision number.

The AssemblyVersionAttribute attribute allows you to specify an asterisk (*) in place of the build or revision number. A version number such as [assembly:AssemblyVersion("1.2.*")] specifies 1 as the major version and 2 as the minor version, and accepts the default build and revision numbers. A version number such as [assembly:AssemblyVersion("1.2.15.*")] specifies 1 as the major version, 2 as the minor version, and 15 as the build number, and accepts the default revision number. The default build number increments daily. The default revision number is the number of seconds since midnight local time (without taking into account time zone adjustments for daylight saving time), divided by 2. If you specify an asterisk for the build number, you can't specify a revision number.

Important

Use of the AssemblyVersionAttribute attribute that specifies an asterisk:

• Makes the build outputs non-reproducible (see Reproducible builds). If the project sets Deterministic build property to true an error CS8357 is reported by the compiler.
• Might degrade build performance, as it prevents build from caching compiler outputs.
• Is incompatible with the Edit & Continue and Hot Reload features.

You can mitigate some of these issues by limiting the use of time-based versions to release builds using conditional compilation, like so:

#if DEBUG
[assembly: AssemblyVersion("1.0.0.0")]
#else
[assembly: AssemblyVersion("1.0.*")]
#endif

A better approach to versioning is to derive the assembly or file version from the HEAD commit SHA (for git repositories). See, for example, Nerdbank.GitVersioning.

The assembly major and minor versions are used as the type library version number when the assembly is exported. Some COM hosts do not accept type libraries with the version number 0.0. Therefore, if you want to expose an assembly to COM clients, set the assembly version explicitly to 1.0 in the AssemblyVersionAttribute page for projects created outside Visual Studio 2005 and with no AssemblyVersionAttribute specified. Do this even when the assembly version is 0.0. All projects created in Visual Studio 2005 have a default assembly version of 1.0.*.

To get the name of an assembly you have loaded, call GetName on the assembly to get an AssemblyName, and then get the Version property. To get the name of an assembly you have not loaded, call GetAssemblyName from your client application to check the assembly version that your application uses.

The AssemblyVersionAttribute attribute can only be applied once. Some Visual Studio project templates already include the attribute. In those projects, adding the attribute in code causes a compiler error.

Constructors

AssemblyVersionAttribute(String)

Initializes a new instance of the AssemblyVersionAttribute class with the version number of the assembly being attributed.

Properties

TypeId	When implemented in a derived class, gets a unique identifier for this Attribute. (Inherited from Attribute)
Version	Gets the version number of the attributed assembly.

Methods

Equals(Object)	Returns a value that indicates whether this instance is equal to a specified object. (Inherited from Attribute)
GetHashCode()	Returns the hash code for this instance. (Inherited from Attribute)
GetType()	Gets the Type of the current instance. (Inherited from Object)
IsDefaultAttribute()	When overridden in a derived class, indicates whether the value of this instance is the default value for the derived class. (Inherited from Attribute)
Match(Object)	When overridden in a derived class, returns a value that indicates whether this instance equals a specified object. (Inherited from Attribute)
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
ToString()	Returns a string that represents the current object. (Inherited from Object)

See also

• Version
• Set assembly attributes
• Assembly versioning
• Metadata and Self-Describing Components
• Managed Execution Process
• Assemblies in .NET