How to get Custom Assembly Attribute with PowerShell

Question

In the AssemblyInfo files of a .net project one can specify a custom assembly attribute via

[assembly: AssemblyMetadata("key1", "value1")]

My question is how does one retrieve this value from a compiled .net assembly via powershell? I'm able to read all the standard attributes like fileversion, companyname, etc. but I'm having a heck of a time getting the value of this custom attribute (key1)

Answer 1

Try something like this:

32# (get-date).GetType().Assembly.GetCustomAttributes([Reflection.AssemblyCopyrightAttribute], $false)

Copyright                                                   TypeId
---------                                                   ------
© Microsoft Corporation.  All rights reserved.              System.Reflection.AssemblyCopyrightAttribute

Instead of get-date use an instance from the assembly you're interested in. Also substitute the Assembly*Attribute that you are interested in retrieving.

In the specific case of AssemblyMetadataAttribute, it is new to .NET 4.5. PowerShell is still on .NET 4.0. So you have to use the reflection only context to get this attribute:

$assembly = [Reflection.Assembly]::ReflectionOnlyLoadFrom("$pwd\ClassLibrary1.dll")
[reflection.customattributedata]::GetCustomAttributes($assembly)

Spits out:

AttributeType                 Constructor                   ConstructorArguments
-------------                 -----------                   --------------------
System.Runtime.Versioning.... Void .ctor(System.String)     {".NETFramework,Version=v4...
System.Reflection.Assembly... Void .ctor(System.String)     {"ClassLibrary1"}
System.Reflection.Assembly... Void .ctor(System.String)     {""}
System.Reflection.Assembly... Void .ctor(System.String)     {""}
System.Reflection.Assembly... Void .ctor(System.String)     {"CDL/TSO"}
System.Reflection.Assembly... Void .ctor(System.String)     {"ClassLibrary1"}
System.Reflection.Assembly... Void .ctor(System.String)     {"Copyright © CDL/TSO 2013"}
System.Reflection.Assembly... Void .ctor(System.String)     {""}
System.Reflection.Assembly... Void .ctor(System.String, ... {"key1", "value1"}
System.Runtime.InteropServ... Void .ctor(Boolean)           {(Boolean)False}
System.Runtime.InteropServ... Void .ctor(System.String)     {"945f04e1-dae3-4de6-adf6-...
System.Reflection.Assembly... Void .ctor(System.String)     {"1.0.0.0"}
System.Diagnostics.Debugga... Void .ctor(DebuggingModes)    {(System.Diagnostics.Debug...
System.Runtime.CompilerSer... Void .ctor(Int32)             {(Int32)8}
System.Runtime.CompilerSer... Void .ctor()                  {}

Note the key1 ane value1 in the output.

Answer 2

Building off @Keith Hill -

$assembly = [Reflection.Assembly]::ReflectionOnlyLoadFrom("$pwd\ClassLibrary1.dll")
$metadata = @{}
[reflection.customattributedata]::GetCustomAttributes($assembly) | Where-Object {$_.AttributeType -like "System.Reflection.AssemblyMetadataAttribute"} | ForEach-Object { $metadata.Add($_.ConstructorArguments[0].Value, $_.ConstructorArguments[1].Value) }

Gets you the AssemblyMetadata converted into a dictionary object. You can get just the value using:

$metadata["key1"]

Resulting in:

value1